No description available.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Bacterial chemotaxis, as observed for Escherichia coli, in a field of chemoattractant molecules is characterised by a run-and-tumble motion. The motion is effected by the clockwise (CW) or counter-clockwise (CCW) rotation of flagella; filamentous appendages attached to molecular motors on the cell body. Runs appear when all flagella turn in the CCW-direction and are used to maintain a favourable direction. Tumbles emerge as soon as one flagellum starts to turn CW and are used for reorientation. Because of the variation observed between individual bacteria displaying run-and-tumble motion, we choose to model this behaviour within a probabilistic framework. An important feature of the chemotactic ability of E.coli is that the cell increases run while moving in the right direction and shortens it in the opposite case. This underlines that tumbles are used for reorientation. It has been found from experiments that there can be significant variation in the tumble fashion depending on the fraction of CW-rotating motors (Turner et al., 2000). The change in angle produced when fewer flagella are rotating CW was found to be smaller when compared to the case for many CW-rotating flagella. In addition, the change of direction contributed by a small portion of CW-rotating flagella is rarely significant for bacteria with many flagella. Based on these observations, we have distinguished between models for the one-flagellated and the multi-flagellated cases. Furthermore, since the tumbling angle change increases with the fraction of CW-rotating motors, it would not be impossible to have some cases where the amount of turn produced by the CW-rotating motors induces the bacterium to have a change of direction greater than 2π. But, this feature could not have been observed because when the bacterium tumbles it can effectuate several revolutions before resuming to a new direction. Therefore, we do not restrict our change of direction to (0,2π) to allow the bacteria to have the possibility to effectuate change of directions of magnitude greater than 2π. To this end, we differentiate between the probability of having directional change of magnitude α and α +2π . Thus we do not use angle change distributions that are defined modulo 2π such as the von Mises distribution or the wrapped normal distribution. The chemotactic ability of the bacterium is modelled by representing the CCW-bias of a single flagellum as a function of the chemoattractant concentration. The model includes the temporal memory of chemoattractant concentration that the bacterium has, which usually spans about 4s. The information about the quality of the current direction of the bacterium is transmitted to the flagellar motor by assuming that this one varies with the chemoattractant concentration level. In addition, the saturation of the bias is incorporated by assuming that the bacterium performs a temporal comparison of the receptor occupancy. The present CCW-bias-Model accounts for the chemotactic ability of the bacterium as well as its adaptation to uniform chemoattractant environment. The models of one-flagellated and multi-flagellated bacterial motion, are used to investigate two main problems. The first one consists of determining the optimal tumbling angle strategy of the bacteria. The second one consists of looking at the effects of the tumble variation on the chemotactic efficiency of the bacteria. In order to address these questions, the chemotactic efficiency measure is defined in such a way that it reflects the ability of the bacteria to converge and to stay in a near neighbourhood of the source so that they gain more nutrients. Since its movement is entirely governed by its single flagellum, the one flagellated bacterium is more able to effectuate a run motion. Tumbling events are modelled to be all equivalent because there is not any fraction of flagella to consider. On the other hand, the tumble variation of the multi-flagellated bacteria is modelled by assuming that the directional change during a tumble is a function of the fraction of CW-rotating motors. By assuming that the number of CW-rotating flagella follows a binomial distribution, we suppose that the multi-flagellated bacteria are less able to effectuate a run motion. This also implies that the change of direction produced by fewer CW-rotating flagella are more likely to happen, and this compensates the lack of run. The models show that the optimal tumbling angle change for the bacteria is less than 2π and that higher flagellated bacteria have higher chemotacitc efficiency. As the number of flagella of the bacteria increases, there can be more tumble variation, in this case the bacteria are more capable of adjusting their direction. There could be some situation were the bacteria are not moving to the right direction, but do not require a large change of direction. This ability to adjust their direction accordingly allows them to converge nearer to the source and to gain more nutrients. In addition, the dependence of the tumbling angle on the fraction of CW-rotating flagella of the mutli-flagellated bacteria, implies that there is a correlation between the tumbling angle deviation and the external environment, because the rotational states CCW-CW of the flagella depends on the external cue. Consequently, it would not be impossible that the average magnitude of tumbling angle change depends on the external environment. To investigate this possibility we analyse the distribution of the tumbling tendency of a single bacterium over time, which is the distribution over time of the average positive tumbling change of the bacterium, within zerogradient environment and within non-zero-gradient environment. We defined the average of these tumbling tendency over time as the directional persistence. We observe that the directional persistence within these different nonzero- gradient environment remains the same. However, the difference between the directional persistence within zero-gradient and non-zeros gradient environment gets larger as the number of flagella of the cell increases. There is more correlation between the external environment and the tumbling tendency of the bacterium. Which is the reason why the higher flagellated bacteria responds the best to the external environment by having the higher chemotactic performance. Finally, the total directional persistence generated by the optimal tumbling angle change of the bacteria is the average directional persistence of the bacteria regardless of their number of flagella. Its value, predicted by the model is 1.54 rad within a non-zero-gradient environment and 1.63 rad within a zero-gradient environment. / AFRIKAANSE OPSOMMING: Bakteriese chemotakse, soos waargeneem word vir Escherichia coli, in ’n veld van chemiese lokmiddel molekules word gekenmerk deur ’n hardloopen- tuimel beweging. Die beweging word bewerkstellig deur die regsom of linksom rotasie van flagella; filamentagtige aanhangsels geheg aan molekulêre motors op die selliggaam. ’n Hardloop aksie kom voor as al die flagella linksom roteer en word gebruik om ’m voordelige koers te handhaaf. Tuimels kom voor sodra een van die flagella regsom draai en word gebruik vir heroriënteering. Van wee die variasie wat waargeneem word tussen individuele bakterieë wat hardloop-en-tuimel bewegiging vertoon, verkies ons ’n probabilistiese raamwerk om in te werk. ’n Belangrike eienskap van die chemotakse vermoë van E. coli is dat die sel meer gereeld hardloop terwyl dit in die regte rigting beweeg en minder gereeld in die teenoorgestelde geval. Dit beklemtoon dat tuimels gebruik word vir heroriënteering. Dit is al eksperimenteel vasgestel dat daar betekenisvolle variasie kan wees in die tuimel wyse, wat afhang van die breukdeel regsom roterende motors (Turner et al., 2000). Die hoekverskil afkomstig van minder regsom roterende flagella was vasgestel om kleiner te wees in vergelyking met die menig regsom roterende geval. Verder word die bydrae tot die hoekverskil van ’n klein breukdeel regsom roterende flagella selde beduidend vir bakterieë met baie flagella. As gevolg van hierdie waarnemings, tref ons onderskeid tussen modelle vir een-flagella en multiflagella gevalle. Aangesien die tuimel hoeksverskil vergroot saam met die breukdeel regsom roterende motore, is dit nie onmoontlik om gevalle te hê waar die hoeveelheid draaiaksie gegenereer deur die regsom roterende motore ’n rigtingsverskil groter as 2π kan bewerkstellig nie. Dit was nie moontlik om hierdie eienskap waar te neem nie aangesien die bakterieë ’n paar keer kan tuimel voordat ’n nuwe rigting vasgestel word. Vir hierdie rede beperk ons nie die hoeksverskil tot (0,2π) nie om die bakterieë toe te laat om rigtings veranderinge groter as 2π te ondergaan. Vir hierdie doel, onderskei ons tussen die waarskynlikheid van ’n rigtinsverskil met grootte α en α + 2π. Dus, gebruik ons nie hoekverskil verspreidings wat modulo 2 gedefinieer is nie, soos die von Mises verspreiding of omwinde normaalverdeling. Die chemotakse vermoë van die bakterium word gemodelleer deur die linksom sydigheid van ’n enkele flagellum as ’n funksie van die chemotakse lokmiddel konsentrasie voor te stel. Die model sluit in die tydelike geheue wat die bakterium besit oor chemotakse lokmiddel konsentrasie, wat gewoonlik oor 4s strek. Die informasie oor die kwaliteit van die huidige rigting van die bakterium word deur gegee na die flagella motor toe deur die aanname te maak dat dit wissel met die chemotakse lokmiddel konsentrasie vlak. Die versadiging van die sydigheid word geinkorporeer deur aan te neem dat die bakterium ’n temporale vergelyking maak tussen reseptor okkupasie. Die huidige linksom sydige model neem die bakterium chemotakse vermoë in ag, as ook aanpassing tot ’n uniforme chemotakse lokmiddel omgewing. Die modelle van een-flagella en multi-flagella bakteriële beweging word gebruik om twee hoof probleme te bestudeer. Die eerste, bestaan daaruit om vas te stel wat die optimale tuimel hoek strategie van die bakterieë is. Die tweede kyk na die uitwerking van tuimel variasie op chemotakse effektiwiteit. In orde om hierdie vra te adreseer word die chemotakse effektiwiteit op so mannier gedefinieer dat dit die bakteriese vermoë om die buurt om die oorsprong te nader en daar te bly. Aangesien die beweging heeltemal vasgestel word deur een flagella, in die een-flagella geval, is ’n bakterium meer in staat daartoe om ’n hardloop aksie te bewerkstellig. Tuimel voorvalle word as ekwivalent gemodeleer omdat daar geen breukdeel roterende flagella is om in ag te neem nie. In teenstelling, word die tuimel variasie van multi-flagella bakterieë gemodeleer deur die aanname te maak dat rigtingsverandering gedurende ’n tuimel ’n funksie is van die breukdeel regsom roterende motore. Deur die aanname te maak dat die getal regsom roterende flagella ’n binomiese verspreiding volg, veronderstel ons dat multi-flagella bakterieë minder in staat daartoe is om ’n hardloop aksie te onderneem. Hierdie impliseer ook dat rigtingverandering wat geproduseer word deur minder regsom roterende flagella meer geneig is om voor te kom en dan kompenseer vir ’n tekortkoming aan hardloop gebeure. Die modelle wys dat die optimale tuimelhoek verandering minder as 2 is en dat bakterieë met meer flagella meer chemotaksies effektief is. Soos die getal flagella vermeder, kan daar meer tuimel variasie wees, en in die geval is die bakterieë meer in staat om hul rigting te verander. Daar kan omstandighede wees waar die bakterieë nie in die regtige rigting beweeg nie, maar nie ’n groot rigtingsverskil nodig het nie. Hierdie vermoë om hul rigting byvolglik te verander stel hul in staat om nader aan die oorsprong te konvergeer en dus meer voedingstowwe op te neem. Die afhanklikheid van die tuimel hoek op die breukdeel regsom roterende flagella van multi-flagella bakterieë dui daarop dat daar ’n korrelasie is tussen die tuimel hoek afwyking en die eksterne omgewing, omdat die roterings toestand, regs- of linksom, van die flagella afhanklik is van die eksterne sein. As ’n gevolg, is dit nie onmoontlik dat die gemiddelde grootte van die tuimel hoek verandering van die eksterne omgewing afhang nie. Om hierdie moontlikheid te bestudeer, analiseer ons die verspreiding van die tuimel neiging van ’n enkele bakterium oor tyd, wat die verspreiding oor tyd van die gemiddelde positiewe tuimel verandering is, in ’n nulgradient en nie-nul-gradient omgewing. Ons het hierdie gemiddelde tuimel neigings oor tyd gedefinieer as die rigtings volharding. Ons het waargeneem dat die rigtings volharding binne verskillende nienul- gradient omgewings dieselfde bly. Nogtans is die verskil tussen die rigtings volharding binne nul-gradient en nie-nul-gradient omgewings groter soos die getal flagella vermeder. Daar is meer korrelasie tussen die eksterne omgewing en tuimel neiging van die bakterium. Dit is die rede hoekom bakterieë met meer flagella die beste reageer op die eksterne omgewing deur beter chemotakse effektiwiteit. Ten slotte, die totale rigtings volharding gegenereer deur die optimale tuimel hoek verandering is die gemiddelde rigtings volharding ongeag van die getal flagella. Die waarde wat deur die model voorspel word is 1.54 rad binne ’n nie-nul-gradient omgewing en 1.63 rad binne ’n nul-gradient omgewing.

Thromboxane A2 receptor (TP) has been shown to play important roles in multiple aspects of cancer development including regulation of tumor growth, survival and metastasis. Molecular mechanisms of TP mediated cancer cell invasion remain to be identified. TP agonist, I-BOP, significantly elevated several matrix metalloproteinases (MMPs) including MMP-1, MMP-3, MMP-9 and MMP-10 in A549 human lung adenocarcinoma cells overexpressing TPα (A549-TPα) or TPβ (A549-TPβ). Signaling pathways of I-BOP-induced MMP-1 expression were examined in further detail as a model system for MMPs induction. Signaling molecules involved in I-BOP-induced MMP-1 expression were identified by using specific inhibitors including small interfering (si)-RNAs of signaling molecules and promoter reporter assay. The results indicate that I-BOP-induced MMP-1 expression is mediated by protein kinase C (PKC), extracellular signal-regulated kinase (ERK)-activator protein-1(AP-1) and ERK-CCAAT/enhancer-binding protein β (C/EBPβ) pathways. I-BOP-induced cellular invasiveness of A549-TPα cells was blocked by, GM6001, a general inhibitor of MMPs. Knockdown of MMP-1 and MMP-9 by their respective siRNA partially reduced I-BOP-stimulated A549-TPα cells invasion suggesting that other MMPs induced by I-BOP were also involved. Furthermore, secreted MMP-1 in conditioned media from I-BOP-treated A549-TPα cells (CM-I-BOP) autocrinely induced monocyte chemoattractant protein-1 (MCP-1) expression. The induction of MCP-1 by MMP-1 in A549 cells was via activation of protease-activated receptor 2 (PAR2) instead of commonly assumed PAR1. This conclusion was reached from the following findings: (1) expression of MCP-1 induced by trypsin, a PAR2 agonist, was inhibited by a PAR2 antagonist. (2) expression of MCP-1 induced by MMP-1 and by CM-I-BOP was blocked by a PAR2 antagonist but not by other PAR antagonists; (3) expression of MCP-1 induced by MMP-1 and by CM-I-BOP was attenuated significantly by pretreatment of cells with PAR2-siRNA. Finally, MCP-1 also can be induced by direct activation of TP in a SP1 involved mechanism. CM-I-BOP enhanced MCP-1-dependent migration of RAW 264.7 macrophages. Co-culture of A549 cells with RAW 264.7 macrophages induced expression of MMPs, VEGF and MCP-1 genes, and increased the invasive potential in A549 cells. My studies provide molecular mechanisms by which TP-mediated cancer cell invasion and suggest that TP is a potential anti-cancer drug target.

Thesis (Ph.D.)--University of Central Florida, 2009. / Adviser: Kiminobu Sugaya. Includes bibliographical references (p. 45-50).

The presence of inflammation in the progression of fatty liver disease induced by fasting was determined in mink. Tumour necrosis factor alpha (TNF-?), and monocyte chemoattractant protein 1 (MCP-1) liver mRNA levels were quantified by real-time PCR. Mink fasted for 5 and 7 days had significantly higher levels of TNF-? and MCP-1 liver mRNA, compared to mink fasted for 0, 1, and 3 days. Mink fasted for 7 days, but re-fed for 28 days had the lowest mRNA levels of both TNF-?, and MCP-1 demonstrating the liver’s ability to restore homeostasis post-fasting. TNF-? mRNA levels were correlated with MCP-1 liver mRNA and liver fat percent. To confirm the physical presence of inflammation, slides stained with haematoxylin and eosin were analyzed for bile ducts resulting in no significant differences. Results indicate that elevated MCP-1 and TNF-? expression are associated with fasting induced fatty liver in mink.

Cardiovascular diseases are the number one cause of death in Western societies. Endothelial dysfunction is an early event in the pathology of atherosclerosis, which is an underlying cause in the majority of cardiovascular events. Exposure to persistent environmental pollutants, such as polychlorinated biphenyls (PCBs), is a risk factor for the development of atherosclerosis. First, we tested a hypothesis that coplanar PCBs, dioxin-like chemicals with affinity for aryl hydrocarbon receptor (AhR), can stimulate up-regulation of monocyte chemoattractant protein-1 (MCP-1), an endothelium-derived chemokine that attracts monocytes into sub-endothelial space in early stages of atherosclerosis. Coplanar PCBs 77 and 126 increased expression of MCP-1 in endothelial cells, and this effect was dependent on activation of AhR and increased levels of cytochrome P450 monoxygenases. Subsequent rise in the levels of reactive oxygen species (ROS) led to a downstream stimulation of redox-sensitive kinases and transcription factors. Lipid rafts, and particularly caveolae, are enriched in endothelial cells, and down-regulation of caveolin-1, a key structural protein of caveolae, decreases the progression of atherosclerosis. Studies using deletion of caveolin-1 in vitro and in vivo demonstrated that intact caveolae were required for up-regulation of MCP-1 and pro-inflammatory interleukin-6 (IL-6) by PCB77. Nutrition can modulate adverse outcomes of human exposure to environmental chemicals. Fish oil-derived long-chain omega-3 polyunsaturated fatty acids, such as docosahexaenoic acid (DHA, 22:6ω-3), can alleviate inflammatory responses and the risk of cardiovascular disease. Cyclopentenone metabolites produced by oxidation of DHA contribute to these protective effects. Endothelial cells were pre-treated with oxidized DHA (oxDHA), prepared by incubation of the fatty acid with a free radical generator. Subsequent up-regulation of MCP-1 by coplanar PCB77 was markedly reduced. DHA-derived cyclopentenones increased nuclear translocation and DNA binding of a transcription factor NF-E2-related factor-2 (Nrf2), as well as expression levels of its target, antioxidant enzyme NAD(P)H:quinone oxidoreductase (NQO1). This stimulation of antioxidant responses prevented ROS production and inflammatory responses induced by PCB77. These data support the concept that nutrition prevents toxicity caused by environmental pollutants; thus, nutrition and can be a sensible approach to alleviate chronic pathologies associated with these chemicals.

Sponges are the descendants of the oldest members of the metazoan phylogenetic lineage and their genome contains animal specific genes but lack true tissues, organ systems, and neurons. Thus, the sponge model system can be used to elucidate origin of developmental processes. The PSED (RDGN) network (Pax/Six/Eya/Dac) is important in development of eyes, muscles, and other structures in Bilaterians. Similarly, sponges contain a precursor Pax-Six gene network. The Ephydatia muelleri (Em) PaxB protein binds to a Pax2/5/8 consensus sequence site and two cis-regulatory elements upstream and one intron sequence of EmSix1/2 (Rivera et al., 2013). This study aimed to determine if transcription factor EmSix1/2 binds upstream of EmPaxB using gel shift mobility assays, identify other downstream targets of EmSix1/2 using DNA immunoprecipitation, and to identify the recognition sequence of Six in sponges through sequencing. In conclusion, purified EmSix binds to DNA specific fragments (1 and 3), which may contain enhancer sequences located in the PaxB promoter region.Possible consensus recognition sequence of Six in sponges were also identified. The host immune response has various mechanisms to protect the organism from infections and invasions of microorganisms and cell damaging chemicals. One such mechanism is the elimination of reactive oxygen species aided by superoxide dismutase (SOD). A study showed that anti-neutrophil chemotactic factor antibodies recognize Tritrichomonas foetus SOD (Granger et al., 1997). During first casualties, SOD is released and triggers a host immune response. The parasites could use SOD to counter oxidative attacks by the leukocytes and damaged cells to protect surrounding parasites. We used the parasite Trichomonas vaginalis that causes trichomoniasis to determine if SOD acts a neutrophil (or other leukocyte) chemotactic factor in this parasite and characterize the expression and secretions of epithelial cells when treated with SOD6. HeLa cells treated with SOD6 showed an increase in the expression of IL-8 chemokine relative to TrxR treated cells. Scratch test assays showed that SOD may act as a macrophage chemoattractant as compared to TrxR but further tests are needed to confirm this.

Sinorhizobium meliloti is a nitrogen-fixing endosymbiont of the legume Medicago sativa commonly known as alfalfa. It uses flagellar rotation and chemotaxis to seek roots of host plants to inhabit. This symbiosis serves as a great model system for studying biological nitrogen fixation and plant-microbe interactions. Since alfalfa brings enormous economic value to the USA, investments into the knowledge of the chemotaxis process that initiates symbiosis have the ability to mitigate deterioration of the environment and significantly increase food supply. The chemotaxis system in the enteric bacteria Escherichia coli is well studied and has been a great resource to understanding the process in other bacterial systems including our model organism S. meliloti. This dissertation compares and contrasts the chemotaxis features in E. coli and S. meliloti and investigates their molecular functions. Based on the understanding gained so far, we attempt to offer plausible explanations for the underlying mechanisms of the S. meliloti chemotaxis pathway. Chapter 1 describes why biological nitrogen fixation is important for agriculture and the health of our environment. This chapter also sheds light on the symbiotic relationship between alfalfa and S. meliloti, which culminates in the formation of nitrogen fixing nodules. We expound on the chemotaxis systems in E. coli and other bacteria including S. meliloti and Bacillus subtilis. In chapter 2, we compare the distribution of C-terminal pentapeptide-bearing receptors and the adaptation proteins that they tether in E. coli and S. meliloti. The stoichiometry data show that the ratio of pentapeptide-bearing chemoreceptors to chemotaxis protein (Che)R and CheB molecules are approximately 500- and 160-fold higher in S. meliloti than in E. coli, respectively. Since not all chemoreceptors in chemotactic bacteria have and utilize the pentapeptide moiety, we investigated the S. meliloti system and observed a strong interaction between CheR, activated CheB and the isolated pentapeptides via in-vitro binding studies. On the contrary, unmodified CheB showed weak binding to the pentapeptide. Through in-vivo studies, we highlighted the physiological necessity of the pentapeptide for chemotaxis. S. meliloti strains with substitutions of the conserved tryptophan residue to alanine in one or all four pentapeptide-bearing Methyl-accepting Chemotaxis Proteins (MCPs) resulted in diminished or loss of chemotaxis to glycine betaine, lysine, and acetate, ligands sensed by pentapeptide-bearing McpX and pentapeptide-lacking McpU and McpV, respectively. The flexible linker connecting the pentapeptide to the MCPs together with the pentapeptide itself were shown to be functional on pentapeptide-lacking chemoreceptors and provided adaptational assistance to other chemoreceptors that lacked a functional pentapeptide. Based on these results, we concluded that S. meliloti employs a pentapeptide-dependent adaptation system with MCPs possessing a consensus pentapeptide motif (N/D)WE(E/N)F). Finally, we postulated that the higher abundance of CheR and CheB in S. meliloti compared to E. coli compensates for the lower number of pentapeptide-bearing chemoreceptors in the chemosensory array. In chapter 3, we explored the putative phosphatase function of a novel protein, CheT, on phosphorylated S. meliloti response regulators. The kinase CheA phosphorylates both the sink response regulator, CheY1, and the flagellar motor interacting response regulator, CheY2. CheY1 competes with CheY2 for these phosphate groups, but we have discovered another layer of complexity to the story. Sequence comparison of S. meliloti CheT and the E. coli phosphatase CheZ shows little sequence homology. However, both proteins share a DXXXQ phosphatase motif. Phosphorylation assays performed using radiolabeled [γ-32P]-ATP revealed that CheT acts as a phosphatase of CheY1~P and accelerates dephosphorylation of CheY1~P by at least two-fold. Interestingly, we also discovered that CheT interacts with CheR, but this interaction did not affect the enzymatic activity of either protein under the examined conditions. Unexpectedly, a cheT deletion strain and strains carrying mutations in the phosphatase motif exhibit an increased swimming speed, a phenotype that does not conform with the model that the absence of CheT or its activity results in increased CheY2~P levels and reduced swimming speed. We concluded that a revised S. meliloti signal termination pathway should include CheT enhancing dephosphorylation of CheY1~P and sensory adaptation involving the yet unknown function of CheT on CheR. While the adaptation system in S. meliloti is unexplored, this work provides first insights into fascinating deviations and similarities to the known paradigm. We have also delivered evidence that the S. meliloti signal termination system requires a dedicated phosphatase. The knowledge gained here takes us a step closer to enhance the S. meliloti chemotaxis pathway towards improved symbiosis with alfalfa and to reduce our dependence on environmentally deleterious synthetic fertilizers. / Doctor of Philosophy / Like all living things, bacteria inhabit a constantly changing environment, hence the need to take up and process this information. Bacterial cells have evolved sophisticated biological tools to tackle this challenge of detecting, responding and adapting to environmental signals like nutrients, toxins, temperature changes, light, metabolites, etc. Motile bacteria such as Escherichia coli, a gut resident microbe, and Sinorhizobium meliloti, a soil dwelling bacterium, direct their swimming behavior in response to chemical gradients within the milieu through a process termed chemotaxis. Generally, this vital process enables a bacterium to escape harmful chemicals and gravitate towards beneficial ones. However, S. meliloti specifically employs chemotaxis to locate the roots of its plant host (alfalfa) and to establish a symbiotic relationship through which the bacteria provide essential nitrogen for plant growth in exchange for nourishment. The biological tools employed by S. meliloti for chemotaxis include environmental sensing receptors called Methyl-accepting Chemotaxis Proteins (MCPs) and proteins inside the bacterial cell that transfer information from the sensors to long, helical rotating propeller structures, called flagella. Importantly, the efficiency of this process hinges on a timely termination of information flow and the ability to adapt to prevailing stimuli while maintaining sensitivity to increasing concentration gradients. This work investigates the function of the C-terminal five amino acid motif of MCPs known to be critical for adaptation in E. coli and the phosphatase activity of a novel protein, CheT, in signal termination of S. meliloti chemotaxis system.

Traumatic Brain Injury (TBI) is one of the leading causes of death and disability among young adults and has been a significant field in medical research over the past decades. Intensive studies focusing on how to repair tissue damage resulting from head injuries have discovered that the central nervous system (CNS) retains a regenerative capacity throughout life due to the persistent presence of neural stem/progenitor cells (NS/NPCs) in the neurogenic regions. In the normal brain, cells generated in the subventricular zone (SVZ) migrate along the rostral migratory stream (RMS) to the olfactory bulb and cells in the subgranular zone (SGZ) migrate laterally into the granule cell layer of the dentate gyrus. Directed movement of these NS/NPCs is controlled by a variety of factors, and among them the chemoattractant SDF-1 is of particular importance. Studies have identified that the chemokine SDF-1α and its receptor CXCR4 play an important role in guiding cell migration in many types of cells including NS/NPCs. The current study tested if SDF-1 could be delivered through alginate to attract and guide migration of NS/NPCs and its progeny both in vitro and in vivo. Using a Boyden chamber migration assay, we found SDF-1α either added directly in the medium or incorporated into alginate threads was capable of influencing migration of cultured NS/NPCs in a dose-dependent manner. In the in vivo study, when injected directly into the cerebral cortex, SDF-1  showed limited capability in inducing neuroblasts migration off the normal tract to the site of SDF-1 injection. When SDF-1 was delivered via alginate thread to the focal injury site at 2 days post TBI, significantly increased number of migrating neuroblasts derived from the SVZ was observed around the injury site. Increased expression of SDF-1 receptor CXCR4 was observed in the NS/NPCs in the SVZ and around the injury site following TBI. These data suggest that bioactive SDF-1α can be delivered via alginate thread and exogenous delivery of SDF-1α and its interaction with receptor CXCR4 mediates migration of newly generated neurons from the SVZ to the site of injury following TBI. Collectively, our study indicates that SDF-1α could be utilized as a guidance cue for tissue repair following brain injury.

Introdução: A nefrite lúpica (NL) é o maior preditor de morbidade e mortalidade em pacientes portadores de lupus eritematoso sistêmico. Recentes estudos mostram que a proteína quimiotática de monócitos (MCP-1) está implicada na ativação de células inflamatórias, afetando a progressão e a severidade da NL, e que a excreção urinária do MCP-1 (uMCP-1) está aumentada em pacientes com NL em atividade. Na literatura os dados sobre o polimorfismo do gene MCP-1 A(-2518)G e do seu receptor CCR2 V(-64)I sobre a susceptibilidade para nefrite lúpica ainda estão em discussão. Objetivos: Avaliar a associação entre o polimorfismo do gene MCP-1 e do seu receptor CCR2 em pacientes com NL e indivíduos saudáveis, além da associação de ambos os polimorfismos com parâmetros clínicos e histológicos nos pacientes portadores de NL. Além disso, avaliar a associação entre a excreção urinária do MCP-1 em pacientes portadores de nefrite lúpica em atividade com parâmetros clínicos e histológicos. Pacientes e Métodos: As genotipagens do MCP-1 e do CCR2 foram realizadas em 197 pacientes com nefrite lúpica através da extração do DNA genômico, seguido da técnica de reação em cadeia da polimerase, utilizando-se primers específicos. A dosagem urinária do MCP-1 foi realizada em 34 pacientes com nefrite lúpica em atividade através da técnica de ELISA. Resultados: Foram estudados 197 pacientes portadores de nefrite lúpica, do sexo feminino, com idade média de 28±9,8 anos, sendo 65,5% de etnia branca e 34,5% não-branca, acompanhados em nosso ambulatório durante o período de 69±37,1 meses. Como grupo controle, utilizou-se um grupo de 220 indivíduos saudáveis do sexo feminino, pareados de acordo com idade e etnia. Quanto à distribuição do genótipo do MCP-1, evidenciou-se que a freqüência do genótipo GG foi significativamente maior nos pacientes portadores de nefrite lúpica quando comparado ao grupo controle (12,7%x5,0%) (p=0,019), enquanto que o genótipo AA apresentou maior freqüência no grupo controle, porém sem significância estatística (48,7%x56,8%). Com relação aos alelos, a freqüência do alelo A foi significativamente maior no grupo controle (75,9%x68%) (p=0,007) quando comparada aos pacientes com NL. Já em relação ao polimorfismo do CCR2, não foi observada nenhuma diferença na freqüência do genótipo entre os dois grupos, porém foi observada maior freqüência do alelo V no grupo controle (89,8%x86,3%) (p=0,046). Não houve associação entre o genótipo e alelos do MCP-1 e do CCR2 com a função renal no início e no final do estudo, marcadores imunológicos, manifestações clínicas (SLEDAI) e a classe histológica. Porém, observou-se um predomínio significante dos flares moderado e grave nos pacientes portadores dos genótipos AA e AG (p< 0,05) em relação ao genótipo GG, enquanto que, em relação à distribuição alélica do MCP-1 e ao CCR2, não se notou diferença estatística. Não se evidenciou diferença estatística entre as curvas de sobrevida renal funcional dos pacientes portadores de nefrite lúpica e os genótipos do MCP-1 e CCR2 e seus respectivos alelos. Notou-se diferença estatística na variação da creatinina sérica ao longo do seguimento (p<0,001). Foram também estudados 34 pacientes portadores de nefrite lúpica em atividade, do sexo feminino, com idade média de 28,4 ± 9,9 anos, sendo 26,5% pacientes de etnia branca e 73,5% de etnia não-branca. A dosagem do MCP-1 urinário foi realizada no início do quadro e após 3 e 6 meses de seguimento. Em relação ao uMCP-1, houve um aumento significante do mesmo no início do quadro renal quando comparado com 3 e 6 meses de tratamento (p<0,05). Evidenciou-se um aumento do uMCP-1 nos pacientes que apresentavam creatinina plasmática inicial > 1,2mg/dl (p<0,05), porém não houve associação entre uMCP-1 e a creatinina após 6 meses de tratamento. Não se observou associação entre os níveis de uMCP-1 com as manifestações clínicas (SLEDAI), classe histológica e marcadores imunológicos, exceto quanto ao anticorpo antifosfolípide, pois houve excreção aumentada do uMCP-1 em pacientes com anticorpo antifosfolípide positivo no início do quadro (p<0,05). Notou-se valores elevados do uMCP-1 nos pacientes que apresentaram flares grave e moderado em relação ao flare leve (p<0,05). Quanto à distribuição genotípica do MCP-1 em relação ao uMCP-1, foi observado uma associação do uMCP-1 em pacientes portadores dos genótipos AG e AA quando comparados ao genótipo GG (p<0,05). Já em relação à distribuição genotípica e alélica do CCR2, não se notou nenhuma diferença na freqüência dos mesmos e a dosagem de uMCP-1. Conclusões: Houve uma significante associação do genótipo GG do polimorfismo do MCP-1 em pacientes portadoras de NL na população estudada, além de uma associação entre os níveis do uMCP-1 com a severidade do flare renal e a função renal nas pacientes portadoras de NL. / Introduction: Lupus Nephritis (LN) contributes substantially to morbidity and mortality in patients with systemic lupus erythematosus. Literature data show monocyte chemoattractant protein (MCP-1) is implicated in the activation of inflamatory cells and has been suggested to affect the progression and severity of lupus nephritis and urinary MCP-1 levels (uMCP-1) are increased in LN patients during active renal disease. Literature data about genotype polymorphism of MCP-1 A(-2518)G and of its receptor CCR2 V(-64)I and susceptibility to LN is still open to discussion. Objectives: The aim of our protocol was to study association of the genotype polymorphism of MCP-1 and CCR2 with LN compared to a healthy matched population and study association these polymorphisms with clinical and histological parameters in LN patients. Moreover, investigate the relationship of uMCP-1 on the onset, severity and resolution of LN flare. Patients and Methods: Genomic DNA was extracted from peripheral leukocytes from 197 LN patients and MCP-1 and CCR2 genomic variants were detected by polymerase chain reaction followed by restriction enzyme-fragment analysis. uMCP-1 levels were mesured by enzyme-linked immunosorbent assay from 34 LN flare patients. Results: One hundred and ninety seven (197) female patients with histological diagnosis de LN undergoing follow up in our institution and 220 ethnically matched healthy controls were enrolled in this study. Epidemiological characteristics of the LN group were: age 28±9.8 years, race 65.5% of caucasians and 34.5% of Brazilian afro-south-latins. Baseline values were collected at the onset of LN and final values in their last follow up (69±37.1 months). There was a significant association of the GG genotype polymorphism of MCP-1 with LN patients compared to controls (12.7%x5.0%) (p=0.019), while the allele A distribuition was associated with healthy controls (75.9%x68%) (p=0.007). Considering CCR2 -64 V/I polymorphism genotype there was a association of the allele V with the control group compared to LN (89.8%x86.3%) (p=0.046). Analyzing genotype polymorphism of MCP-1 and CCR2 there werent correlation with renal function, immunological markers, clinical manifestations (SLEDAI) or histological classes of LN. There was a significant association of the AA and AG genotypes polymorphism of MCP-1 with moderate and severe renal flares compared to GG genotype polymorphism of MCP-1 (p< 0.05). Kaplan-Meier analysis of the renal survival curves with respect to the studied genotypes did not show any influence in the progression of renal disease. There was a significant association of the creatinine onset and on follow up (p<0.001). Thrity four (34) female patients with criteria for active LN and histological diagnosis were enrolled and treated for six months. Each patient was evaluated once a month and uMCP-1 bimonthly. Epidemiological characteristics of the group showed: age 28.4±9.9 years and race 26.5% caucasians and 73.5% Brazilian afro-south-latins. uMCP-1 excretion at onset (T0) of LN was significantly increased when compared to uMCP-1 measured on the third (T3) and sixth months (T6) (p<0.05). Analyzing uMCP-1 values on T0 there was a correlation with creatinine (p<0,05), but not with, clinical manifestations histological classes of LN or immunological markers, except in patients with positive antiphospholipid autoantibodies demonstrated increased of uMCP-1 (p<0.05). Otherwise, uMCP-1 levels were associated with seriousness of nephritis flares, severe and moderate over mild (p<0.05). Considering MCP-1 polymorphism genotype there was association of the AA and AG genotypes with increased uMCP-1 in patients with active renal disease (p<0.05). Conclusions: There is a significant association of the GG genotype of MCP-1 -2518 A/G polymorphism with LN in our population. uMCP-1 levels in LN is associated with flare seriousness and renal function.