Interaction between Programmed cell death-1 (PD-1), a member of costimulatory molecules, and its receptors Programmed cell Death-1 Ligand 1 (PD-L1) and Programmed cell Death-1 Ligand 2 (PD-L2), play an important role in the negative regulation of immune reactions. It was shown that a polymorphism in a regulatory site of the PD-1 gene was associated with susceptibility to several autoimmune diseases in various ethnic groups, whereas the contribution of the PD-1 gene or its ligand genes to the onset of type 1 diabetes (T1D) mellitus in the Japanese population remains unknown. We first screened PD-1, PD-L1, and PD-L2 genes for polymorphisms in the Japanese population, and then investigated the frequencies of polymorphisms in patients with T1D mellitus in comparison with healthy controls. In total, we identified 26 polymorphic sites within these genes, and then 23 polymorphisms with minor allele frequencies greater than 5% were intensively analyzed for genotyping in the patients and the controls. As a result, allele and genotype frequencies of the polymorphism numbers 2, 3, 4, 5, 6, and 8 in the PD-1 gene were different to some extent between the patients and the controls with P < 0.05, which did not reach statistical significance after the correction of multiple comparisons. Allele or genotype frequencies of any SNPs in the PD-L1 or PD-L2 gene did not show differences between the patients and the controls. The frequencies of the estimated haplotypes, those of which consisted of polymorphism numbers 2, 3, 4, 5, 6, and 8 in the PD-1, were significantly different between the patients and the controls (P = 0.00095). The in vitro assessment for a transcription activity of each haplotype of the PD-1 gene by luciferase assay did not demonstrate a functional difference between the haplotypes. In conclusion, the genetic evaluation by association study demonstrated that the PD-1 gene was a predisposing gene to the development of T1D mellitus in the Japanese population.
A growing body of evidence has shown that oxidative stress may be involved in the development of vascular complications associated with diabetes. However, the molecular mechanism for increased reactive oxygen species (ROS) production in diabetes remains uncertain. Among various possible mechanisms, attention have increasingly been paid to NAD(P)H oxidase as the most important source of ROS production in vascular cells. High glucose level stimulates ROS production through protein kinase C (PKC)-dependent activation of vascular NAD(P)H oxidase. Furthermore, the expression of NAD(P)H oxidase components is increased in micro- and macrovascular tissues of diabetic animals in association with various functional disorders and histochemical abnormalities. These results suggest that vascular NAD(P)H oxidase-driven ROS production may contribute to the onset or development of diabetic micro- or macrovascular complications. In this point of view, the possible new strategy of antioxidative therapy for diabetic vascular complications is discussed in this review.
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