Cytochrome P450 (CYP) 2A6 catalyzes nicotine C-oxidation, leading to cotinine formation, a major metabolic pathway of nicotine in humans. There are genetic polymorphisms in the human CYP2A6 gene. Previously, we demonstrated that in vivo nicotine metabolism is impaired with the CYP2A6*4, CYP2A6*7, and CYP2A6*10 alleles in Japanese subjects and Korean subjects. An allele possessing a point mutation in the TATA box termed CYP2A6*9 (T-48G) has been reported to decrease the transcriptional activity in vitro as assessed by luciferase assay. In this study we investigated the effects of the CYP2A6*9 allele on in vivo enzymatic activity by evaluating nicotine metabolism. The mutation of T-48G was found only on the CYP2A6*1A allele but not on the CYP2A6*1B allele. Allele frequencies of CYP2A6*9 in Japanese subjects (n = 92) and Korean subjects (n = 209) were 21.3% and 22.3%, respectively. In Korean subjects the cotinine/nicotine ratios as an index of nicotine metabolism in the subjects with CYP2A6*9/CYP2A6*9 (4.3 +/- 2.4) were significantly lower than those in the subjects with CYP2A6*1A/CYP2A6*9 (7.7 +/- 5.6) and CYP2A6*1A/CYP2A6*1A (10.4 +/- 9.2) (P <.05 and P <.005, respectively). In Japanese subjects a similar result was observed, although it was not significant. Thus it is suggested that the mutation in the TATA box (CYP2A6*9 allele) caused the decreased in vivo enzymatic activity. With an in vitro study, it was shown that the expression levels of CYP2A6 messenger ribonucleic acid and coumarin 7-hydroxylase activity in human livers genotyped as CYP2A6*1/CYP2A6*9 and CYP2A6*9/CYP2A6*9 tended to be lower than those in human livers genotyped as CYP2A6*1/CYP2A6*1, although there was no significant difference because of the small number of samples. These in vitro data supported the in vivo data demonstrating that the CYP2A6*9 allele caused the decreased expression level and enzymatic activity of CYP2A6.

Peroxisome proliferator-activated receptor ␥ coactivator (PGC)-1 is a critical transcriptional regulator of energy metabolism. Here we found that PGC-1␣ is a short lived and aggregation-prone protein. PGC-1␣ localized throughout the nucleoplasm and was rapidly destroyed via the ubiquitin-proteasome pathway. Upon proteasome inhibition, PGC-1␣ formed insoluble polyubiquitinated aggregates. Ubiquitination of PGC-1␣ depended on the integrity of the C terminus-containing arginine-serine-rich domains and an RNA recognition motif. Interestingly, ectopically expressed C-terminal fragment of PGC-1␣ was autonomously ubiquitinated and aggregated with promyelocytic leukemia protein. Cooperation of the N-terminal region containing two PEST-like motifs was required for prevention of aggregation and targeting of the polyubiquitinated PGC-1␣ for degradation. This region thereby negatively controlled the aggregation properties of the C-terminal region to regulate protein turnover and intranuclear compartmentalization of PGC-1␣. Exogenous expression of the PGC-1␣ C-terminal fragment interfered with degradation of full-length PGC-1␣ and enhanced its coactivation properties. We concluded that PGC-1␣ function is critically regulated at multiple steps via intramolecular cooperation among several distinct structural domains of the protein.

Lipocalin-type prostaglandin D synthase (L-PGDS), which was originally identified as an enzyme responsible for PGD 2 biosynthesis in the brain, is highly expressed in the myocardium, including in cardiomyocytes. However, the factors that control expression of the gene encoding L-PGDS and the pathophysiologic role of L-PGDS in cardiomyocytes are poorly understood. In the present study, we demonstrate that glucocorticoids, which act as repressors of prostaglandin biosynthesis in most cell types, upregulated the expression of L-PGDS together with cytosolic calcium-dependent phospholipase A2 and COX2 via the glucocorticoid receptor (GR) in rat cardiomyocytes. Accordingly, PGD 2 was the most prominently induced prostaglandin in vivo in mouse hearts and in vitro in cultured rat cardiomyocytes after exposure to GR-selective agonists. In isolated Langendorff-perfused mouse hearts, dexamethasone alleviated ischemia/reperfusion injury. This cardioprotective effect was completely abrogated by either pharmacologic inhibition of COX2 or disruption of the gene encoding L-PGDS. In in vivo ischemia/reperfusion experiments, dexamethasone reduced infarct size in wild-type mice. This cardioprotective effect of dexamethasone was markedly reduced in L-PGDS-deficient mice. In cultured rat cardiomyocytes, PGD 2 protected against cell death induced by anoxia/reoxygenation via the D-type prostanoid receptor and the ERK1/2-mediated pathway. Taken together, these results suggest what we believe to be a novel interaction between glucocorticoid-GR signaling and the cardiomyocyte survival pathway mediated by the arachidonic acid cascade.

The authors propose the use of the terms "RExP," "RDP," and "transitional zone," instead of RExZ, which cannot be well defined. The RDP appears to be a good landmark for use during microvascular decompression.