Hokkaido University (北海道大学) / 博士 / 医学

Background: Type 1 Diabetes mellitus (TIDM) is a chronic disorder in which the insulin producing beta cells are selectively self-destroyed. Although the etiology of the disease has not been determined, genetic dispositions such as SLC11A1 polymorphism in suffering patients have been reported. The role of pathogenic microorganisms such as Mycobacterium avium subspecies paratuberculosis (MAP) in TIDM has also been recently debated. MAP is already known to cause paratuberculosis in cattle and now it is a strong suspect of causing autoimmune diseases in humans such as Crohn’s disease, multiple sclerosis, autoimmune Thyroiditis, rheumatoid arthritis and autoimmune diabetes. We hypothesis that molecular mimicry between MAP Heat shock protein 65K (Hsp65) and human Glutamic Acid Decarboxylase 65K (GAD65) can be the trigger which leads to the autoimmune destruction of beta cell in patients exposed to MAP . Method: To test the hypothesis, peptide sequences of MAP Hsp65 and human GAD65 were investigated using BLAST and PyMOL bioinformatics tools. Moreover, 18 blood samples from humans with TIDM and controls, and 100 sera samples from cattle with paratuberculosis and controls were evaluated for the presence of MAP, MAP DNA and its antibodies. Glucose, insulin and GAD65 antibodies were also determined in some of the clinical samples. Results: Peptide BLAST analysis revealed 44% identity between the two proteins with 75% positive identities in a 16 amino acid region. PyMOL structural analysis identified possible shared epitope regions of the proteins in its 3D conformation. Immunoblot analysis revealed a strong cross reactivity between lysate of E.coli recombinant of MAP Hsp65 and plasma from human subject with TIDM. A weak cross reactivity was also observed between healthy rat pancreatic homogenate and rabbit anti MAP IgG. Nested PCR using IS900-specific iv oligonucleotide primers did not detect MAP DNA in peripheral blood from 18 subjects with Type I Diabetes, Type II Diabetes and non-diabetic controls. Long term culture of leukocytes from blood samples from same subjects resulted in the presence of MAP in 3/10 (30%) TIDM and 4/8 (50%) control subjects. However anti MAP IgG were detected in 5/10 (50 %) TIDM samples compared to 3/8 (37.5 %) controls. Insulin level was measured in sera from paratuberculosis cattle and controls. In MAP infected cattle, insulin level ranged from below 0.1ng/ml to 2.456 ng/ml with an average of 0.36 +/- 0.57ng/ml compared to below 0.1ng/ml to 13.47ng/ml with an average of 2.86 +/- 3.00ng/ml in healthy cattle. Conclusion: Bioinformatics analysis between MAP Hsp65 and human GAD65 through BLAST and PyMOL analysis revealed a homology of 16 amino acid motif and possible shared epitope regions; immunohistochemistry analysis revealed a cross reactivity between rabbit antiMAP IgG and pancreatic cell homogenate from a healthy rat. Moreover, plasma from patient with TIDM (TD8), who was confirmed to be positive for MAP DNA and MAP IgG, reacted strongly with MAP Hsp65 in MAP protein lysate and MAP Hsp65 recombinant clone pmptb20. Culture of MAP from human leukocytes is significant despite the lack of correlation between MAP in samples from TIDM and controls. It is worth noting that some of the control subjects have not been evaluated for other autoimmune diseases possible MAP role. Additionally, antiMAP IgG levels in TIDM subjects compared to controls have raised a suspicion on the involvement of MAP in TIDM. The poor correlation of MAP in blood versus either the antiMAP IgG or the insulin level may be related with the fastidious nature of MAP and in vitro cultivation. Since MAP is the sole causative agent of Johne’s disease, it is significant that the insulin level is 8 folds less in MAP infected cattle compared to MAP free cattle. Overall, the data v is mixed and suggest that further study is needed to investigate the intriguing question to whether MAP is involved in TIDM or not.

L'étude qu'on a entreprise a pour but d'analyser les facteurs de virulence des espèces "Classiques" et "nouvelles" de Brucella. Dans cette perspective, on a analysé les génomes des espèces récemment découvertes : Brucella inopinata BO1 et Brucella inopinata-like BO2, isolés pour la première fois de patients humains sans réservoir animal connu. On a découvert que ces deux espèces possèdent des profils de restriction uniques. De plus, BO2 possède deux chromosomes de taille identique, un profil jamais décrit pour une autre espèce de Brucella. L'analyse de la réplication intracellulaire de ces deux espèces révèle que BO2 ne se réplique pas dans les macrophages humains et murins alors que BO1 se réplique d'une façon similaire à Brucella suis 1330, ce qui confirme la potentielle implication de BO1 dans la pathogenèse chez l'homme. Sur un autre niveau d'analyse, on a été à la recherche de facteurs de virulence potentiels dans d'autres espèces de Brucella notamment Brucella microti et Brucella suis sur les niveaux génomique et post-transcriptionnel. Sur le niveau génomique, on a découvert que le système GAD (glutamate decarboxylase) confère une résistance à l'acidité à Brucella microti lors de son passage dans l'estomac. Sur le niveau post-transcriptionnel, on a isolé, séquencé et identifié les petits ARNs noncodant associés à la protéine chaperone Hfq, qui joue un rôle important dans la virulence de Brucella. / We have undertaken in this study a multidimensional analysis of the virulence factors of "Classical" and new "Brucella species". In this objective, we have analysed the genomes of newly described species Brucella inopinata BO1 and Brucella inopinata-like BO2 isolated for the first time from human patients with no known animal reservoir. We found that these two species have unique restriction profiles. In addition, BO2 has a unique chromosomal distribution with two chromosomes of the same size, never seen before in Brucella. Analysis of the intracellular replication of these strains reveals that BO2 is unable to replicate in neither human nor mouse macrophages while BO1 successfully entered and replicated as efficiently as Brucella suis 1330 confirming the potential virulence of this species for humans. On an other level of analysis, we looked for potential virulence factors in other Brucella species including Brucella microti and Brucella suis at the genomic and post-transcriptional level. At the genomic level we discovered that the glutamate decarboxylase system confers resistance to acidity to Brucella miroti during its transit in the stomach. On the post-transcriptional level, we isolated, sequenced and identified small noncoding RNAs associated to the chaperone protein Hfq, known to play a role in the virulence of Brucella.

The fetal lung epithelium secretes fluid into the potential pulmonary air-spaces by actively transporting chloride (Cl¯) into the lung lumen. This Cl¯-driven fluid secretion declines with the progression of lung development. Recent studies demonstrate that the A-type γ-aminobutyric acid receptor (GABAAR), a Cl¯ channel, and glutamic acid decarboxylase (GAD65/67), key GABA-synthesizing enzymes, are expressed in adult pulmonary epithelial cells (ECs), forming an autocrine GABAAR signaling system. My thesis study revealed that GABAAR π- and β2- subunits are expressed in high levels in the fetal rat lung epithelium and decline at birth, consistent with pattern of fluid secretion. Immunohistochemistry showed distinct profiles of expression for GABAAR subunits and GAD65/67. Treatment of alveolar ECs with dexamethasone reduced the GABAAR π-subunit expression. These results suggest that the GABAAR signaling in the fetal pulmonary epithelium is developmentally regulated and the GABAAR expression and GABAAR-mediated Cl¯ secretion in pulmonary ECs may be regulated by glucosteroids.

The fetal lung epithelium secretes fluid into the potential pulmonary air-spaces by actively transporting chloride (Cl¯) into the lung lumen. This Cl¯-driven fluid secretion declines with the progression of lung development. Recent studies demonstrate that the A-type γ-aminobutyric acid receptor (GABAAR), a Cl¯ channel, and glutamic acid decarboxylase (GAD65/67), key GABA-synthesizing enzymes, are expressed in adult pulmonary epithelial cells (ECs), forming an autocrine GABAAR signaling system. My thesis study revealed that GABAAR π- and β2- subunits are expressed in high levels in the fetal rat lung epithelium and decline at birth, consistent with pattern of fluid secretion. Immunohistochemistry showed distinct profiles of expression for GABAAR subunits and GAD65/67. Treatment of alveolar ECs with dexamethasone reduced the GABAAR π-subunit expression. These results suggest that the GABAAR signaling in the fetal pulmonary epithelium is developmentally regulated and the GABAAR expression and GABAAR-mediated Cl¯ secretion in pulmonary ECs may be regulated by glucosteroids.

蛋白激酶CK2（Casine kinase 2）為四單體所構成，針對配受質蛋白之絲胺酸或蘇胺酸位置進行磷酸化，先前研究已經發現在紋狀體腦區之CK2的表現量與活性皆高於大腦中其餘腦區，而紋狀體腦區主要神經細胞為-氨基丁酸神經元（GABAergic neurons）的medium spiny neuron（MSN），會受到來自黑質多巴胺神經細胞（dopaminergic neurons）的調控。此外，DARPP-32（dopamine- and cAMP-regulated phosphoprotein, Mr 32 kDA）蛋白亦被發現大量表現於在MSN細胞中，且為CK2之受質蛋白質。雖然CK2已被證實參與多巴胺神經元的神經保護機制，但是否參與MSN細胞對運動行為調控之生理機制仍未清楚。由於已有研究發現施予1-甲基-4-苯基-1,2,3,6-四氢吡啶（MPTP）藥物處理造成黑質-紋狀體腦區受損之老鼠腦內-氨基丁酸（GABA）的生合成酵素─麩胺酸脫羧酵素67（GAD67）表現量與正常老鼠不同，因此本論文研究的主題擬在大鼠實驗模式中利用MPP+造成投射至紋狀體之多巴胺神經細胞受損，探討當多巴胺調控紋狀體神經細胞能力缺失的狀態下，MSN細胞之CK2、DARPP-32和GAD蛋白表現與動物運動行為之相關性。 實驗結果發現，直接於紋狀體給予1-甲基-4-苯基碘化啶 （MPP+ Iodide）皆會造成CK2、DARPP-32以及GAD67之蛋白質含量的減少，多巴胺及其代謝物和GABA等神經化學傳遞物質亦有減少的現象；另外，在MPP+給予前分別操弄CK2或DARPP-32 胺基酸Ser102磷酸化的表現，皆會改變GAD67蛋白質含量與黑質酪胺酸羥化酶（Tyrosine Hydroxylase, TH）蛋白質含量，同時神經化學傳遞物質的含量或代謝亦有改變。由現有之結果推測CK2/DARPP-32/GAD67細胞訊息傳遞機制可能參與巴金森氏症運動行為失常之細胞層面的調控。 / Protein kinase CK2 is a heterotetrameric and serine/threonine protein kinase. Its protein levels and activity are found to be elevated in the striatum when compared to other brain areas. CK2 is known to involve in the neuroprotective effects of dopaminergic neurons, whether it also regulates the neuronal function relative to motor behaviors is still unclear. DARPP-32 protein is known as one of the substrates for CK2 and is highly expressed in the GABAergic medium spiny neurons (MSN) responsible for dopamine stimulation in the striatum. Furthermore, other studies have indicated that the expression of glutamic acid decarboxylase 67 (GAD67) mRNA and protein was different in the striatum of MPTP vs. naïve animals, which is one of the enzymes responsible for the synthesis of neurotransmitter GABA. In the present study, we observed that the parallel changes in protein levels of CK2, DARPP-32 and GAD67 in the striatum and TH in the substantia nigra of MPP+-treated. We also found that manipulation of CK2 or DARPP-32 gene expression aggravated the MPP+-induced neuropathological dificts. The present results suggest that CK2/DARPP-32/GAD67 signaling pathway might involve in the cellular mechanism of motor-deficit in Parkinson’s disease.