Thesis (Ph. D.)--School of Pharmacy. University of Missouri--Kansas City, 2006. / "A dissertation in pharmaceutical sciences and pharmacology." Advisor: Srikumaran Melethil. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Dec. 20, 2007. Includes bibliographical references (leaves 159-192). Online version of the print edition.

Dendritic cells (DCs) form a key component of the immune response, as they are involved in the innate and adaptive immunity and in the process of tolerance. Under normal conditions, DCs are absent from the Central Nervous System (CNS), as the blood brain barrier (BBB) restricts their entry. However, DCs have recently been implicated in the pathogenesis of several CNS diseases. The molecular mechanisms that mediate DC trafficking across the BBB are poorly understood. The objectives of this study were to examine the role of endothelial cell adhesion molecules (eCAMs) and their ligands in the process of DC adhesion to the BBB endothelium, and to investigate the participation of DCs in human CNS diseases. To study DC adhesion, DCs were generated in vitro by culturing human blood monocytes in the presence of GM-CSF and IL- 4, and DC maturation was induced by adding inflammatory cytokines (TNF-α, IL-1β, IL-6) and PGE₂. Immature and mature DCs displayed differences in their expression of surface molecules, including eCAM ligands, by flow cytometry. Adhesion to the cerebral endothelium was investigated using an in vitro model of the BBB consisting of primary cultures of human brain microvessel endothelial cells (HBMEC). Immature or mature DCs were incubated with resting or TNF-α-activated HBMEC for up to one hour. Only a few DCs adhered to resting HBMEC, but adhesion was upregulated upon activating HBMEC (p<O.Ol). Moreover, immature DCs adhered to activated HBMEC to a greater extent compared to mature DCs (p<O.OOl). Blocking experiments indicated that the adhesion of both immature and mature DCs to HBMEC was dependent upon ICAM-1-CD18 or ICAM-2-CD18, ICAM-2-DC-SIGN, and PECAM-l PECAM-l interactions. In addition, VCAM-1-VLA-4 interactions mediated the adhesion of immature but not mature DCs to activated HBMEC. Using immunohistochemistry for DC markers, we also examined the presence of DCs in human inflammatory, infectious, and neurodegenerative diseases, stroke and tumours. The results indicate accumulation of DC SIGN—, fascin—, and MHC class Il—expressing DCs in the CNS under most pathological conditions. These findings provide further insight into the mechanisms of neuroinflammation, and highlight the role of DCs and the BBB endothelium in this process.

The blood-brain barrier (BBB) is located at the level of the cerebral microvasculature and is critical to maintain central nervous system (CNS) homeostasis. The tight junction (TJ) protein complexes between endothelial cells at the BBB are primarily responsible for limiting paracellular diffusion of substances from the blood to the CNS. The BBB’s functional integrity is compromised in a number of disease states which affect the CNS, suggesting BBB dysfunction causes or contributes to many diseases of the CNS. A common component of most of these diseases is oxidative stres. Oxidative stress is associated with hypoxia-reoxygenation (HR) and peripheral inflammatory pain (PIP). Both HR and PIP have been shown to compromise BBB functional integrity. Using in vivo rat models of HR and PIP, we examined the role of ROS on BBB permeability as well as the TJ protein occludin using the free radical scavenger tempol. First, we subjected rats to HR with or without pre-treatment with tempol (200 mg/kg). We showed that tempol prevents up-regulation of the cellular stress marker heat shock protein 70 at the BBB during HR. Next we showed tempol reverses HR-mediated BBB permeability increase to ¹⁴C-sucrose, a marker of BBB paracellular permeability. Tempol also attenuated changes in the structure and localization of occludin, suggesting ROS produced during HR alter occludin and lead to disruption of BBB. We then investigated whether ROS production have similar effects on occludin and BBB permeability during PIP by administering 3% λ-carrageenan into the hind paw of rats. We found tempol attenuated carrageenan-induced increase in paw edema and thermal hyperalgesia. Tempol also attenuated up-regulation of the cellular stress marker NF-κB in cerebral microvessels. Tempol significantly decreased BBB permeability to ¹⁴C sucrose during PIP. We found PIP reduces disulfide bonds in occludin oligomeric assemblies thought to be important in maintaining the structural integrity of the BBB. Tempol significantly inhibited disulfide bond reduction, suggesting ROS mediate BBB disruption during inflammatory pain by reducing occludin disulfide bonding. Taken together, these findings show the involvement of ROS during HR and PIP contributes to BBB dysfunction by altering the structure of high molecular weight occludin oligomeric assemblies.

P-glycoprotein (Pgp; ABCB1) is a well known transporter involved in energy-dependent-drug efflux activity. At the brain capillary endothelium, its luminal membrane location is ideal for its ascribed role in the physiological efflux of a wide array of structurally and functionally diverse compounds from the brain. This is a critical issue in regards to the delivery of central nervous system (CNS)-acting therapeutics. Moreover, a dysregulation of Pgp has been implicated in specific CNS disease states, including Alzheimer's disease, epilepsy, and brain cancer where an upregulation of Pgp has been well established as a mediator of multi-drug resistance. Inflammation is a common component in all of these conditions. Previously our laboratory has reported changes in BBB molecular and functional properties during inflammatory pain (Huber et al. 2001). This has led us to investigate the effects of peripheral inflammatory pain on Pgp efflux transport properties at the BBB, in vivo. In the present study we examined the effects of lambda-carrageenan-induced inflammatory pain (i.e. hyperalgesia; CIP) on the molecular and functional properties of Pgp at the BBB. Western blots using enriched fractions of isolated rat brain microvessels revealed that Pgp expression at the BBB was increased by CIP and that this increase occurred predominantly within the membrane region of the cell. Additionally, both in situ brain perfusions and whole body antinociceptive profiling of the Pgp substrate and opioid analgesic, [3H] morphine, indicate that changes in Pgp at the BBB, mediated by peripheral inflammation, can impact brain uptake of morphine. To further elucidate the mechanism(s) behind the rapid upregulation (3 h) of Pgp at this region, we explored regulation of Pgp at the plasma membrane. Our findings show that CIP induces a movement of Pgp within these domains and that Pgp co-localizes with caveolin-1 and clathrin, key structural proteins associated with caveolae and clathrin-pit lipid rafts, respectively. Our data indicate for the first time that peripheral inflammatory pain induces functional and molecular changes in Pgp, a critical efflux transporter, at the BBB in vivo and that these alterations may be mediated in part via a proteolipidic re-organization mechanism.

The blood-brain barrier (BBB) is located at the level of the cerebral microcapillaries, and functions to maintain environmental homeostasis by allowing the neurons access to the required nutrients and enabling the exchange of metabolic waste. BBB dysfunction has been observed in a number of pathophysiologic statres including peripheral inflammatory pain (Huber et al., 2001b). Using the lamda-carrageenan inflammatory pain (CIP) model, we observed alterations in the tight junction (TJ) proteins paralleled by an increase in BBB permeability to [14C] sucrose. The mechanisms by which these perturbations occurred remain to be elucidated. In the current study, we investigate the central mechanism for the BBB perturbations under CIP. It is our hypothesis that the modulations of the BBB under CIP, are mediated via a central signaling pathway. First, to investigate the involvement of neuronal input from pain activity on alterations in BBB, we developed a method for inhibiting the nociceptive input from the paw. Using a perineural injection of 0.75% bupivacaine into the right hind leg prior to CIP, we were able inhibit development thermal hyperalgesia induced by CIP, as tested by infrared heat stimulus, without effecting edema formation 1 h post CIP. Upon inhibition of nociception under CIP, there was an attenuation of both the changes in permeability and the changes in tight junction protein expression, with both returning to control levels. Next, we investigated intercellular adhesion molecule-1 (ICAM-1), a key signaling protein at the BBB, which in the presence of proinflammatory mediators, increases in expression leading to the activation of signaling pathways as well as morphological changes. We found a region specific increase in ICAM-1 mRNA and protein expression following CIP which directly correlated with increased expression of activated microglia. Finally, we investigated the influence activated microglia had on BBB permeability. Using an 0.150 mg intrathecal bolus injection of minocycline, a potent inhibitor of microglia activation (Klein and Cunha, 1995), we were able to inhibit the increased expression of activated microglia, and saw an attenuation of permeability to control levels. These findings suggest CIP induced BBB disruption is localized and has a central-mediated component independent of peripheral influence.

Dendritic cells (DCs) form a key component of the immune response, as they are involved in the innate and adaptive immunity and in the process of tolerance. Under normal conditions, DCs are absent from the Central Nervous System (CNS), as the blood brain barrier (BBB) restricts their entry. However, DCs have recently been implicated in the pathogenesis of several CNS diseases. The molecular mechanisms that mediate DC trafficking across the BBB are poorly understood. The objectives of this study were to examine the role of endothelial cell adhesion molecules (eCAMs) and their ligands in the process of DC adhesion to the BBB endothelium, and to investigate the participation of DCs in human CNS diseases. To study DC adhesion, DCs were generated in vitro by culturing human blood monocytes in the presence of GM-CSF and IL- 4, and DC maturation was induced by adding inflammatory cytokines (TNF-α, IL-1β, IL-6) and PGE₂. Immature and mature DCs displayed differences in their expression of surface molecules, including eCAM ligands, by flow cytometry. Adhesion to the cerebral endothelium was investigated using an in vitro model of the BBB consisting of primary cultures of human brain microvessel endothelial cells (HBMEC). Immature or mature DCs were incubated with resting or TNF-α-activated HBMEC for up to one hour. Only a few DCs adhered to resting HBMEC, but adhesion was upregulated upon activating HBMEC (p<O.Ol). Moreover, immature DCs adhered to activated HBMEC to a greater extent compared to mature DCs (p<O.OOl). Blocking experiments indicated that the adhesion of both immature and mature DCs to HBMEC was dependent upon ICAM-1-CD18 or ICAM-2-CD18, ICAM-2-DC-SIGN, and PECAM-l PECAM-l interactions. In addition, VCAM-1-VLA-4 interactions mediated the adhesion of immature but not mature DCs to activated HBMEC. Using immunohistochemistry for DC markers, we also examined the presence of DCs in human inflammatory, infectious, and neurodegenerative diseases, stroke and tumours. The results indicate accumulation of DC SIGN—, fascin—, and MHC class Il—expressing DCs in the CNS under most pathological conditions. These findings provide further insight into the mechanisms of neuroinflammation, and highlight the role of DCs and the BBB endothelium in this process.

The blood-brain barrier (BBB) formed by the brain capillary endothelial cells provides a protective barrier between the systemic blood and the extracellular environment of the central nervous system. Since most fatty acids in the brain enter from the blood, we examined the mechanism of permeability of various fatty acids across primary human brain microvessel endothelial cells (HBMEC). Cardiolipin (CL), a major mitochondrial phospholipid involved in energy metabolism in mammalian mitochondria, and fatty acid transport protein-1 (FATP-1) may regulate the intracellular level of fatty acyl-Coenzyme A’s. Since fatty acids are required for oxidative phosphorylation via mitochondrial oxidation, we also examined the effect of altering FATP-1 levels on CL biosynthesis. The permeability of radiolabeled fatty acids was determined using confluent cells grown on Transwell® inserts following inhibition of various fatty acid transporters. The passage of [1-14C]oleate across confluent HBMEC monolayers was significantly enhanced when fatty acid free albumin was present in the basolateral media. Knockdown of FATP-1, FATP-4, fatty acid translocase/CD36, or fatty acid binding protein 5 significantly decreased permeability of a number of radiolabeled fatty acids across the HBMEC monolayer from either apical as well as basolateral sides. The findings indicate that transport of some fatty acids across HBMEC is, in part, a transcellular process mediated by fatty acid transport proteins. Next, HEK 293 cells were used as a model to determine the effect of altering FATP-1 levels on CL. HEK-293 mock- and FATP-1 siRNA-transfected cells or mock and FATP-1 expressing cells were incubated for 24 h with 0.1 mM oleate bound to albumin (1:1 molar ratio) then incubated for 24 h with 0.1 mM [1,3-3H]glycerol and radioactivity incorporated into CL determined. FATP-1 siRNA-transfected cells exhibited reduced FATP-1 mRNA and increased incorporation of [1,3-3H]glycerol into CL (2-fold, p<0.05) compared to controls indicating elevation in de novo CL biosynthesis. In contrast, expression of FATP-1 resulted a reduction in incorporation of [1,3-3H]glycerol into CL (65%, p<0.05) indicating reduced CL synthesis. In addition, in vitro cytidine-5’-diphosphate-1,2-diacyl-sn-glycerol synthetase (CDS) activity was reduced by exogenous addition of oleoyl-Coenzyme A. The data indicate that CL de novo biosynthesis may be regulated by FATP-1 through CDS-2 expression in HEK 293 cells.

The blood-brain barrier (BBB) formed by the brain capillary endothelial cells provides a protective barrier between the systemic blood and the extracellular environment of the central nervous system. Since most fatty acids in the brain enter from the blood, we examined the mechanism of permeability of various fatty acids across primary human brain microvessel endothelial cells (HBMEC). Cardiolipin (CL), a major mitochondrial phospholipid involved in energy metabolism in mammalian mitochondria, and fatty acid transport protein-1 (FATP-1) may regulate the intracellular level of fatty acyl-Coenzyme A’s. Since fatty acids are required for oxidative phosphorylation via mitochondrial oxidation, we also examined the effect of altering FATP-1 levels on CL biosynthesis. The permeability of radiolabeled fatty acids was determined using confluent cells grown on Transwell® inserts following inhibition of various fatty acid transporters. The passage of [1-14C]oleate across confluent HBMEC monolayers was significantly enhanced when fatty acid free albumin was present in the basolateral media. Knockdown of FATP-1, FATP-4, fatty acid translocase/CD36, or fatty acid binding protein 5 significantly decreased permeability of a number of radiolabeled fatty acids across the HBMEC monolayer from either apical as well as basolateral sides. The findings indicate that transport of some fatty acids across HBMEC is, in part, a transcellular process mediated by fatty acid transport proteins. Next, HEK 293 cells were used as a model to determine the effect of altering FATP-1 levels on CL. HEK-293 mock- and FATP-1 siRNA-transfected cells or mock and FATP-1 expressing cells were incubated for 24 h with 0.1 mM oleate bound to albumin (1:1 molar ratio) then incubated for 24 h with 0.1 mM [1,3-3H]glycerol and radioactivity incorporated into CL determined. FATP-1 siRNA-transfected cells exhibited reduced FATP-1 mRNA and increased incorporation of [1,3-3H]glycerol into CL (2-fold, p<0.05) compared to controls indicating elevation in de novo CL biosynthesis. In contrast, expression of FATP-1 resulted a reduction in incorporation of [1,3-3H]glycerol into CL (65%, p<0.05) indicating reduced CL synthesis. In addition, in vitro cytidine-5’-diphosphate-1,2-diacyl-sn-glycerol synthetase (CDS) activity was reduced by exogenous addition of oleoyl-Coenzyme A. The data indicate that CL de novo biosynthesis may be regulated by FATP-1 through CDS-2 expression in HEK 293 cells.

The blood brain barrier (BBB), formed by endothelial cells lining the lumen of the brain capillaries, is a restrictively permeable interface that only allows transport of specific compounds into the brain. Cardiolipin (CL) is a mitochondrial- specific phospholipid known to be required for the activity and integrity of the respiratory chain. The current study examined the role of cardiolipin in maintaining an optimal mitochondrial function that may be necessary to support the barrier properties of the brain microvessel endothelial cells (BMECs). Endothelial cells have been suggested to obtain most of their energy through an-aerobic glycolysis based on studies of cells that were obtained from the peripheral vasculatures. However, here, we showed that the adult human brain capillary endothelial cell line (hCMEC/D3) appeared to produce ~60% of their basal ATP requirement through mitochondrial oxidative phosphorylation. In addition, RNAi mediated knockdown of the CL biosynthetic enzyme cardiolipin synthase (CLS), although did not grossly affect the mitochondrial coupling efficiency of the hCMEC/D3 cells, did seem to reduce their ability to increase their mitochondrial function under conditions of increased demand. Furthermore, the knockdown appeared to have acted as a metabolic switch causing the hCMEC/D3 cells to become more dependent on glycolysis. These cells also showed increase in [3H]-2-deoxyglucose uptake under a low glucose availability condition, which might have served as a mechanism to compensate for their reduced energy production efficiency. Interestingly, the increase in glucose uptake appeared correlated to an increase in [3H]-2-deoxyglucose glucose transport across the knockdown confluent hCMEC/D3 monolayers grown on Transwell® plates, which was used in our study as an in vitro model for the human BBB. This suggests that changes in the brain endothelial energy status may play a role in regulating glucose transport across the BBB. These observations, perhaps, also explain why the brain capillary endothelial cells were previously observed to possess higher mitochondrial content than those coming from non-BBB regions (Oldendorf et al. 1977).

Thesis (M.D.)--University of Adelaide, Dept. of Surgery, 1984. / Some mounted ill. Includes bibliographical references (leaves 147-194).