Here, we show that three enzymes belonging to the 1B group of the aldo-keto reductase (AKR) superfamily, i.e., human placental aldose reductase (AKR1B1), mouse kidney aldose reductase (AKR1B3) and mouse vas deferens protein (AKR1B7), catalyse the reduction of prostaglandin (PG) H(2), a common intermediate of various prostanoids, to form PGF(2alpha) in the presence of NADPH. AKR1B1, AKR1B3 and AKR1B7 displayed higher affinities for PGH(2) (K(m) = 1.9, 9.3 and 3.8 microM, respectively) and V(max) values (26, 53 and 44 nmol/min/mg protein, respectively) than did the human lung PGF(2alpha) synthase (AKR1C3; 18 microM and 4 nmol/min/mg protein, respectively). The PGF(2alpha) synthase activity of AKR1B1 and AKR1B3 was efficiently inhibited by two AKR inhibitors, tolrestat (K(i) = 3.6 and 0.26 microM, respectively) and sorbinil (K(i) = 21.7 and 0.89 microM, respectively), in a non-competitive or mixed-type manner, whereas that of AKR1B7 was not sensitive to these inhibitors (K(i) = 9.2 and 18 mM, respectively). These data provide a molecular basis for investigating novel functional roles for AKR1B members and PGF(2alpha) as mediators of physiological and pathological processes in mammalian organisms.

Prostaglandin (PG) F 2␣ suppresses adipocyte differentiation by inhibiting the function of peroxisome proliferatoractivated receptor ␥. However, PGF 2␣ synthase (PGFS) in adipocytes remains to be identified. Here, we studied the expression of members of the aldo-keto reductase (AKR) 1B family acting as PGFS during adipogenesis of mouse 3T3-L1 cells. AKR1B3 mRNA was expressed in preadipocytes, and its level increased about 4-fold at day 1 after initiation of adipocyte differentiation, and then quickly decreased the following day to a level lower than that in the preadipocytes. In contrast, the mRNA levels of Akr1b8 and 1b10 were clearly lower than that level of Akr1b3 in preadipocytes and remained unchanged during adipogenesis. The transient increase in Akr1b3 during adipogenesis was also observed by Western blot analysis. The mRNA for the FP receptor, which is selective for PGF 2␣ , was also expressed in preadipocytes. Its level increased about 2-fold within 1 h after the initiation of adipocyte differentiation and was maintained at almost the same level throughout adipocyte differentiation. The small interfering RNA for Akr1b3, but not for Akr1b8 or 1b10, suppressed PGF 2␣ production and enhanced the expression of adipogenic genes such as peroxisome proliferator-activated receptor ␥, fatty acid-binding protein 4 (aP2), and stearoylCoA desaturase. Moreover, an FP receptor agonist, Fluprostenol, suppressed the expression of those adipogenic genes in 3T3-L1 cells; whereas an FP receptor antagonist, AL-8810, efficiently inhibited the suppression of adipogenesis caused by the endogenous PGF 2␣ . These results indicate that AKR1B3 acts as the PGFS in adipocytes and that AKR1B3-produced PGF 2␣ suppressed adipocyte differentiation by acting through FP receptors.

1 Protease-activated receptors (PARs) 1 and 2 modulate the gastric and intestinal smooth muscle motility in vitro. In the present study, we examined if activation of PAR-2 and PAR-1 could alter gastrointestinal transit in mice. 2 Intraperitoneal administration of the PAR-2-activating peptide SLIGRL-NH 2 , but not the inactive control LSIGRL-NH 2 , at 1±5 mmol kg 71 , in combination with the aminopeptidase inhibitor amastatin at 2.5 mmol kg 71 , facilitated gastrointestinal transit in a dose-dependent manner. The human PAR-1-derived peptide SFLLR-NH 2 and the speci®c PAR-1 agonist TFLLR-NH 2 , but not the inactive control FSLLR-NH 2 , at 2.5 ± 10 mmol kg 71 , in combination with amastatin, also promoted gastrointestinal transit. 3 The Ca 2+ -activated, small conductance K + channel inhibitor apamin at 0.01 mmol kg 71 signi®cantly potentiated the actions of SLIGRL-NH 2 and TFLLR-NH 2 at sube ective doses. 4 The increased gastrointestinal transit exerted by either SLIGRL-NH 2 at 5 mmol kg 71 or TFLLR-NH 2 at 10 mmol kg 71 was completely abolished by the L-type Ca 2+ channel inhibitor verapamil at 61.6 mmol kg 71 . In contrast, the tyrosine kinase inhibitor genistein at 18.5 mmol kg 71 failed to modify the e ects of the agonists for PAR-2 or PAR-1. 5 These ®ndings demonstrate that PAR-1 and PAR-2 modulate gastrointestinal transit in mice in vivo. Our data also suggest that the PAR-1-and PAR-2-mediated e ects are modulated by apaminsensitive K + channels and are dependent on activation of L-type Ca 2+ channels, but independent of tyrosine kinase. Our study thus provides novel evidence for the physiological and/or pathophysiological roles of PARs 1 and 2 in the digestive systems, most probably during in¯ammation.

No abstract

Urinary excretion of lipocalin-type PGD 2 synthase (L-PGDS), which converts PG H 2 to PGD 2 , increases in early diabetic nephropathy. In addition, L-PGDS expression in the tubular epithelium increases in adriamycin-induced nephropathy, suggesting that locally produced L-PGDS may promote the development of CKD. In this study, we found that L-PGDS-derived PGD 2 contributes to the progression of renal fibrosis via CRTH2-mediated activation of Th2 lymphocytes. In a mouse model, the tubular epithelium synthesized L-PGDS de novo after unilateral ureteral obstruction (UUO). L-PGDS-knockout mice and CRTH2-knockout mice both exhibited less renal fibrosis, reduced infiltration of Th2 lymphocytes into the cortex, and decreased production of the Th2 cytokines IL-4 and IL-13. Furthermore, oral administration of a CRTH2 antagonist, beginning 3 days after UUO, suppressed the progression of renal fibrosis. Ablation of IL-4 and IL-13 also ameliorated renal fibrosis in the UUO kidney. Taken together, these data suggest that blocking the activation of CRTH2 by PGD 2 might be a strategy to slow the progression of renal fibrosis in CKD.

No abstract

Orally administered rubiscolin-6 may stimulate food intake through COX-2 and leptomeningeal L-PGDS, followed by DP(1) and Y(1) receptors, downstream of the central δ opioid receptor.

Duchenne muscular dystrophy is a fatal muscle wasting disease that is characterized by a deficiency in the protein dystrophin. Previously, we reported that the expression of hematopoietic prostaglandin D synthase (HPGDS) appeared in necrotic muscle fibers from patients with either Duchenne muscular dystrophy or polymyositis. HPGDS is responsible for the production of the inflammatory mediator, prostaglandin D(2). In this paper, we validated the hypothesis that HPGDS has a role in the etiology of muscular necrosis. We investigated the expression of HPGDS/ prostaglandin D(2) signaling using two different mouse models of muscle necrosis, that is, bupivacaine-induced muscle necrosis and the mdx mouse, which has a genetic muscular dystrophy. We treated each mouse model with the HPGDS-specific inhibitor, HQL-79, and measured both necrotic muscle volume and selected cytokine mRNA levels. We confirmed that HPGDS expression was induced in necrotic muscle fibers in both bupivacaine-injected muscle and mdx mice. After administration of HQL-79, necrotic muscle volume was significantly decreased in both mouse models. Additionally, mRNA levels of both CD11b and transforming growth factor beta1 were significantly lower in HQL-79-treated mdx mice than in vehicle-treated animals. We also demonstrated that HQL-79 suppressed prostaglandin D(2) production and improved muscle strength in the mdx mouse. Our results show that HPGDS augments inflammation, which is followed by muscle injury. Furthermore, the inhibition of HPGDS ameliorates muscle necrosis even in cases of genetic muscular dystrophy.