Jyh Cherng Shyu

Fluctuation of serum leptin level in rats after ovariectomy and the influence of estrogen supplement.

In order to understand the mechanism of increasing body fat in perimenopausal and postmenopausal women, an ovariectomy-induced obesity model was used to study the role of leptin. In this investigation, a long-term study lasted for 13 weeks was conducted to monitoring the change of serum leptin level in rats after the loss of estrogen, and also to examine the influence of estrogen replacement. The results showed that three weeks after the removal of ovaries the body weight of Ovx rats was already significantly higher than the other two groups, and continued to gain more weight thereafter. Accompanying with the significant weight gain was the changes in the serum leptin levels. The leptin concentration declined gradually during the first half of experimental period, dropping down to an almost undetectable level at week 7 (0.216+/-0.132 ng/ml). Subsequently, its concentration began to elevate, and by the end of experiment leptin level was significantly higher (3.182+/-0.936 ng/ml) than the value before the operation (0.818+/-0.242 ng/ml). This fluctuation of serum leptin level caused by ovariectomy was eliminated by the replacement of estrogen. The present data indicate that ovariectomy-induced weight gain is caused by the early drop in leptin level. The later rise in leptin production is connected to the increased body weight probably originated from a reduced sensitivity in leptin signal.

Estrous cycle variation of TRPV1-mediated cross-organ sensitization between uterus and NMDA-dependent pelvic-urethra reflex activity

Cross-organ sensitization between the uterus and the lower urinary tract (LUT) underlies the high concurrence of pelvic pain syndrome and LUT dysfunctions, and yet the role of gonadal steroids is still unknown. We tested the hypothesis that cross-organ sensitization on pelvic-urethra reflex activity caused by uterine capsaicin instillation is estrous cycle dependent. When compared with the baseline reflex activity (1.00 +/- 0.00 spikes/stimulation), uterine capsaicin instillation significantly increased reflex activity (45.42 +/- 9.13 spikes/stimulation, P < 0.01, n = 7) that was corroborated by an increase in phosphorylated NMDA NR2B (P < 0.05, n = 4) but not NR2A subunit (P > 0.05, n = 4) expression. Both intrauterine pretreatment with capsazepine (5.02 +/- 2.11 spikes/stimulation, P < 0.01, n = 7) and an intrathecal injection of AP5 (3.21 +/- 0.83 spikes/stimulation, P < 0.01, n = 7) abolished the capsaicin-induced cross-organ sensitization and the increment in the phosphorylated NR2B level (P < 0.05, n = 4). The degrees of the cross-organ sensitization increased in a dose-dependent manner with the concentration of instilled capsaicin from 100 to 300 microM in both the proestrus and metestrus stages, whereas they weakened when the concentrations were higher than 1,000 microM. Moreover, the cross-organ sensitization caused by the uterine capsaicin instillation increased significantly in the rats during the proestrus stage when compared with the metestrus stage (P < 0.01, n = 7). These results suggest that estrogen levels might modulate the cross-organ sensitization between the uterus and the urethra and underlie the high concurrence of pelvic pain syndrome and LUT dysfunctions.

Nicotine-activated descending facilitation on spinal NMDA-dependent reflex potentiation from pontine tegmentum in rats

This study was conducted to investigate the possible neurotransmitter that activates the descending pathways coming from the dorsolateral pontine tegmentum (DPT) to modulate spinal pelvic-urethra reflex potentiation. External urethra sphincter electromyogram (EUSE) activity in response to test stimulation (TS, 1/30 Hz) and repetitive stimulation (RS, 1 Hz) on the pelvic afferent nerve of 63 anesthetized rats were recorded with or without microinjection of nicotinic cholinergic receptor (nAChR) agonists, ACh and nicotine, to the DPT. TS evoked a baseline reflex activity with a single action potential (1.00 +/- 0.00 spikes/stimulation, n = 40), whereas RS produced a long-lasting reflex potentiation (16.14 +/- 0.96 spikes/stimulation, n = 40) that was abolished by d-2-amino-5-phosphonovaleric acid (1.60 +/- 0.89 spikes/stimulation, n = 40) and was attenuated by 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo (F) quinoxaline (7.10 +/- 0.84 spikes/stimulation, n = 40). ACh and nicotine microinjections to DPT both produced facilitation on the RS-induced reflex potentiation (23.57 +/- 2.23 and 28.29 +/- 2.36 spikes/stimulation, P < 0.01, n = 10 and 20, respectively). Pretreatment of selective nicotinic receptor antagonist, chlorisondamine, reversed the facilitation on RS-induced reflex potentiation caused by nicotine (19.41 +/- 1.21 spikes/stimulation, P < 0.01, n = 10) Intrathecal WAY-100635 and spinal transection at the T(1) level both abolished the facilitation on reflex potentiation resulting from the DPT nicotine injection (12.86 +/- 3.13 and 15.57 +/- 1.72 spikes/stimulation, P < 0.01, n = 10 each). Our findings suggest that activation of nAChR at DPT may modulate N-methyl-d-aspartic acid-dependent reflex potentiation via descending serotonergic neurotransmission. This descending modulation may have physiological/pathological relevance in the neural controls of urethral closure.

The activation of matrix metalloproteinase-2 induced by protein kinase C alpha in decidualization†

This study investigated the protein kinase C (PKC) and matrix metalloproteinase‐2 (MMP‐2) in the development of deciduomata in pseudo‐pregnant and pregnant rats. The results showed that the expression of MMP‐2 was significantly increased from day 2 to day 5 in pseudo‐pregnancy and from day 7 to day 9 in pregnancy. To further investigate the correlation between MMP‐2 and protein kinase Cα (PKCα), the expression of MMP‐2 in the 12‐O‐tetradecanoylphorbol 13‐acetate (TPA)‐treated organotypic culture of decidual tissue was determined. The results showed that the active form of MMP‐2 was significantly increased in the TPA‐treated cultures. Moreover, this response was inhibited by the PKC inhibitor H7, the PKCα specific inhibitor Gö‐6976 and the translation inhibitor cycloheximide, but not by the transcription inhibitor actinomycin D or the replication inhibitor mitomycin C. In addition, TPA also reversed the MMP‐2 expression after by progesterone pretreatment in the primary decidual cells. These findings indicate that PKCα may play an important role in the regulation of the MMP‐2 expression during decidualization. J. Cell. Biochem. 108: 547–554, 2009.

Protective Effects of Ocimum gratissimum Polyphenol Extract on Carbon Tetrachloride-Induced Liver Fibrosis in Rats

Ocimum gratissimum found in tropical regions is a traditional herb commonly which prevents free radical damage and protects liver from oxidative stress and fibrosis. Ocimum gratissimum polyphenol extract (OGPE) was purified by resin tube to 33.24% polyphenol and 8.2% flavonoid, which were three-fold higher compared with the pre-purification concentrations. The abstract was used to determine if the antioxidant components in the O. gratissimum extract (OGE) were responsible for protective effects on liver fibrosis. High-performance liquid chromatography analysis revealed that the content levels of catechin, caffeic acid and epicatechin in OGPE also increased three-fold. Male Wistar rats were administered with carbon tetrachloride (CCl₄) and varying amounts of OGPE doses [0-12 mg/kg body weight (BW)] or OGE dose (40 mg/kg BW) for 8 weeks. Results showed that OGPE at 12 mg/kg BW, similar to OGE at 40 mg/kg BW, maintained the liver weight, significantly ameliorated CCl₄-induced steatosis, and mitigated other pathological changes. OGPE (12 mg/kg BW) also maintained the levels of serum alanine aminotransferase and aspartate aminotransferase, as well as the levels of malondialdehyde, catalase and α-smooth muscle actin in liver tissues from CCl₄-induced changes. These findings suggest that antioxidant components in OGPE were the major factors that prevented liver fibrosis. Moreover, higher polyphenol concentrations were necessary for higher effectiveness.