In both humans and rodents, males are known to be more susceptible than females to hepatocarcinogenesis. We have previously reported that glycine N-methyltransferase (GNMT) interacts with aflatoxin B 1 (AFB 1 ) and reduces both AFB 1 -DNA adduct formation and hepatocellular carcinoma (HCC) in mice. We also reported that 50% of the males and 100% of the females in a small group of Gnmt null (Gnmt2/2) mice developed HCC, with first dysplastic hepatocellular nodules detected at mean ages of 17 and 16.5 months, respectively. In our study, we tested our hypothesis that male and female Gnmt2/2 mice are susceptible to AFB 1 carcinogenesis, and that the absence of Gnmt expression may accelerate AFB 1 -induced liver tumorigenesis. We inoculated Gnmt2/2 and wild-type mice intraperitoneally with AFB 1 at 7 days and 9 weeks of age and periodically examined them using ultrasound. Dysplastic hepatocellular nodules were detected in six of eight males and five of five females at 12.7 and 12 months of ages, respectively. Dysplastic hepatocellular nodules from 5/8 (62.5%) male and 4/ 5 (80%) female Gnmt2/2 mice were diagnosed as having HCC,~6 months earlier than AFB 1 -treated wild-type mice. Results from microarray and real-time PCR analyses indicate that five detoxification pathway-related genes were downregulated in AFB 1 -treated Gnmt2/2 mice: Cyp1a2, Cyp3a44, Cyp2d22, Gsta4 and Abca8a. In summary, we observed overall higher susceptibility to AFB 1 -related HCC in Gnmt2/2 mice, further evidence that GNMT overexpression is an important contributing factor to liver cancer resistance.Human hepatocarcinogenesis is a multistage process with multifactorial etiology, including genetic and environmental interactions. The risk factors associated with HCC include chronic infection with the hepatitis B or C virus, exposure to dietary aflatoxin B1 (AFB 1 ) on moldy corn and vegetables, and that simultaneous infection with hepatitis B virus and ingestion of AFB 1 leads to a synergistic increase in liver carcinogenesis and HCC.1 Two unusual phenomena have been observed in the epidemiology of human hepatocellular carcinoma (HCC): (i) high morbidity in sub-Saharan Africa and eastern Asia, implying a large prevalence of HBV and the contamination of foodstuffs with AFB 1 and (ii) regardless of region, HCC is more prevalent in males, with reported maleto-female ratios in most countries ranging from 2:1 to 6:1. 1-3Aflatoxin ingestion has been identified as a major risk factor for HCC development in Africa and Asia.4-6 AFB 1 epoxide binds covalently to DNA and induces G-to-T transversions at the third base in codon 249 of the p53 gene. 7,8 Male mice have been shown to be more susceptible than female mice to AFB 1 -induced liver tumor formation, 9,10 and multiple proteins are known to be capable of binding with AFB 1 in rat liver cytosols. 11We recently reported that glycine N-methyltransferase (GNMT) can bind with AFB 1 and inhibits DNA adduct formation. 12 We also used AFB 1 to challenge GNMT transgenic mice intraperitoneally. After 11 months, w...

The effect of exercise on the production of ovarian progesterone was examined in female rats. During in vivo experiments, diestrous rats were catheterized via the right jugular vein (RJV), and blood samples were collected before and after 10, 15, 30, and 60 min of swimming. In addition, blood samples were collected from the RJV before and 2, 5, 10, 15, 30, 60, and 120 min after 10 min of infusion of lactate (13 mg.kg-1.min-1) through the left femoral vein. To explore if lactate modulates progesterone secretion by acting directly on rat ovary or on anterior pituitary gland (AP), an in vitro experiment that mimicked the in vivo condition was performed. The ovarian tissue was challenged with lactate (0.01-10 mM) or porcine follicle-stimulating hormone (1 microgram/ml) and 3-isobutyl-1-methylxanthine (1 mM) for 60 min, and the AP was challenged with lactate ranging from 0.1 to 10 mM or 10 nM gonadotropin-releasing hormone for 30 min. The postexercise levels of plasma glucose, lactate, and progesterone at 10, 15, and 30 min were significantly higher than the corresponding basal levels. Plasma luteinizing hormone (LH) did not change after exercise. An elevation of plasma lactate and progesterone was found at 15 and 30 min subsequent to 10 min of infusion of lactate. Lactate ranging from 0.01 to 10 mM significantly increased ovarian adenosine 3',5'-cyclic monophosphate (cAMP) and progesterone production in a dose-dependent manner. LH concentration in plasma was not changed subsequent to lactate infusion. LH level in media samples was not altered after incubation of AP with lactate. These results suggest that the increase of plasma progesterone level in rats during exercise is independent of LH secretion and at least in part is due directly to a stimulatory effect of lactate on the production of ovarian cAMP.

GNMT regulates genes related to detoxification and anti-oxidation pathways. BaP is a liver cancer carcinogen especially during GNMT deficiency.

The hypothalamic neuropeptide gonadotropin-releasing hormone (GnRH) serves a key role in regulating mammalian reproductive function. An extrapituitary role for GnRH in the normal and malignant reproductive tissues has been postulated. The purpose of our study is to demonstrate the presence and levels of GnRH receptor (RGnRH) protein and its mRNA in normal and malignant tissues of ovary. Normal human ovarian tissues (n = 13), as well as epithelial ovarian cancer specimens from stages I-IV (n = 39), were obtained from appropriate patients at operation room. Monoclonal antibodies against RGnRH were used for immunohistochemical evaluation of paraffin-embedded ovarian tissue sections by methods of streptavidin-biotin immunostaining. The molecular size and levels of RGnRH were determined by enhanced chemiluminescence-Western blot assay. The amount of RGnRH mRNA was detected by reverse transcriptase polymerase chain reaction (RT-PCR). The rate of positive immunostaining in ovarian cancers was 53.8% (21/39). The rate of positive staining in the late stage (stages III and IV) was significantly higher than that in the early stage (stages I and II). A single band of molecular weight of about 60 kDa was detected from protein extracts of ovarian cancer as well as from normal ovary. The mean values of fold increase of signal intensities of 60 kDa detected by Western blots in stages I-IV ovarian cancers were 2.39, 2.42, 2.78, and 3.62, respectively, as compared with normal ovarian tissues. The overall positive rate of Western blot analysis for ovarian cancers was 59% (23/39). The mean values of signal intensity of RT-PCR products of RGnRH mRNA in stages I-IV were 2.24, 2.58, 3.10, and 3.20, respectively. The positive rate of overexpression of RGnRH mRNA in ovarian cancer was 70% (21/30). The differences of mean values of signal intensities of Western blot staining (2.41 versus 2.85) as well as RT-PCR products (2.40 versus 3.11) between the early stage and the late stage of ovarian cancers were statistically nonsignificant. Mechanism of autocrine regulation of tumor growth in human epithelial ovarian cancer can be explained by the coexistence of GnRH, RGnRH, and its mRNA, according to our own and other studies. The level of RGnRH expressed by ovarian cancer might be used for targeting chemotherapeutic agents to those patients who harbor RGnRH-positive tumors.

Glucocorticoids (GCs) have been employed as immunosuppressive agents for many years. However, it is still unclear how GCs instantly uncouple T cells from acute stressful inflammatory. In terms of time scale, the genomic activity of the classic GC receptor cannot fulfill this role under crisis; but a rapid non-genomic response can. In a previous study, intracellular acidification was found to be due to a rapid non-genomic inhibition of Na(+)/H(+)-exchange 1 (NHE1) and this event led to the immunosuppression of T cell proliferation by progesterone. The aim of this study was to examine whether there is a rapid acidification response caused by an inhibition of NHE1 activity and to explore the differential non-genomic effect on immunosuppression of hydrocortisone and dexamethasone. The IC(50) values for NHE1-dependent pH(i) recovery by hydrocortisone and dexamethasone are 250 and 1 nM, respectively. Co-stimulation of GCs with phytohemagglutinin (PHA) is able to inhibit PHA-induced IL-2 secretion, IL-4 secretion, and T-cell proliferation. Furthermore, apoptosis in PHA-activated T cells is not induced by hydrocortisone but by dexamethasone. The mechanism of immunosuppression on proliferation by dexamethasone was found to be different of hydrocortisone and seems to involve cytotoxicity against T cells. Moreover, apoptosis induced by dexamethasone and impermeable dexamethasone-bovine serum albumin suggests that the apoptotic immunosuppression occurs through both the plasma membrane and cytoplasmic sites. The rapid inhibitory responses triggered by GCs would seem to release T cells instantly when an acute stress-related response is needed. Nonetheless, the apoptotic immunosuppression by dexamethasone is attributable to its severe cytotoxicity.