The expression and regulation of the PGE receptors, EP2 and EP4, both of which are coupled to the stimulation of adenylate cyclase, were examined in peritoneal resident macrophages from C3H/HeN mice. mRNA expression of EP4 but not EP2 was found in nonstimulated cells, but the latter was induced by medium change alone, and this induction was augmented by LPS. mRNA expression of EP4 was down-regulated by LPS but not by medium change. PGE2 increased the cAMP content of both LPS-treated and nontreated cells. ONO-604, an EP4 agonist, also increased cAMP content in nonstimulated cells and in cells treated with LPS for 3 h, but not for 6 h. Butaprost, an EP2 agonist, was effective only in the cells treated with LPS for 6 h. The inhibitory effects of ONO-604 on TNF-α and IL-12 production were equipotent with PGE2 at any time point, but the inhibitory effects of butaprost were only seen from 14 h after stimulation. PGE2 or dibutyryl cAMP alone, but not butaprost, reduced EP4 expression, and indomethacin reversed the LPS-induced down-regulation of EP4, indicating that the down-regulation of EP4 is mediated by LPS-induced PG synthesis and EP4 activation. Indeed, when we used C3H/HeJ (LPS-hyporesponsive) macrophages, such reduction in EP4 expression was found in the cells treated with PGE2 alone, but not in LPS-treated cells. In contrast, up-regulation of EP2 expression was again observed in LPS-treated C3H/HeJ macrophages. These results suggest that EP4 is involved mainly in the inhibition of cytokine release, and that the gene expression of EP2 and EP4 is differentially regulated during macrophage activation.

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.

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An environmental isolate of Salmonella Enteritidis (SE), grown to the logarithmic phase, rapidly lost culturability by the addition of 3 mM H2O2 to cultures grown in Luria-Bertani (LB) medium; however, some H2O2-treated bacteria regained their culturability in M9 minimal medium, if sodium pyruvate was present at at least 0.3 mM. In addition, most pyruvate analogues, such as bromopyruvate or phenylpyruvate, did not show restoration activity similar to that of pyruvate, except in the case of α-ketobutyrate. Further analysis of the mechanism underlying the resuscitation by pyruvate revealed that although many of the bacteria showed respiratory activity on CTC (5-cyano-2,3-di-(p-tolyl) tetrazolium chloride) reduction with or without pyruvate, the biosynthesis of DNA and protein synthesis were quite different in the presence or absence of pyruvate, i.e., pyruvate endowed the cells with the ability to incorporate much more radio-label into precursors during the resuscitation process. These results suggest that pyruvate is one of the key molecules working in the resuscitation process by taking bacteria from the non-culturable state to the growing and colony-forming state by triggering the synthesis of macromolecules such as DNA and protein.