Phosphatidylcholine attenuated docetaxel-induced peripheral neurotoxicity in rats.

Docetaxel is a taxane chemotherapeutic agent used in the treatment of breast cancer, prostate cancer and gastric cancer, but several side effects such as peripheral neurotoxicity could occur. The present study was designed to investigate the therapeutic potential of phosphatidylcholine (PC) on docetaxel-induced peripheral neurotoxicity. Rats were randomly divided into three groups and treated for 4 weeks. Behavioral tests were conducted to measure the effects of PC on docetaxel-induced decreases in mechanical & thermal nociceptive threshold. Biochemical tests were conducted to measure the level of oxidative stress on sciatic nerve. Histopathological and immunohistochemical experiments were also conducted to assess neuronal damage and glial activation. PC treatment significantly attenuated docetaxel-induced changes in mechanical & thermal nociceptive response latencies. PC decreased oxidative stress in sciatic nerve by increasing antioxidant levels (glutathione, glutathione peroxidase and superoxide dismutase activity). In immunohistochemical evaluation, PC treatment ameliorated docetaxel-induced neuronal damage and microglial activation in the sciatic nerve and spinal cord. Thus, PC showed protective effects against docetaxel-induced peripheral neurotoxicity. These effects may be attributed to its antioxidant properties and modulation of microglia.

Signaling pathway of lysophosphatidic Acid-induced contraction in feline esophageal smooth muscle cells.

Lysolipids such as LPA, S1P and SPC have diverse biological activities including cell proliferation, differentiation, and migration. We investigated signaling pathways of LPA-induced contraction in feline esophageal smooth muscle cells. We used freshly isolated smooth muscle cells and permeabilized cells from cat esophagus to measure the length of cells. Maximal contraction occurred at 10(-6) M and the response peaked at 30s. To identify LPA receptor subtypes in cells, western blot analysis was performed with antibodies to LPA receptor subtypes. LPA1 and LPA3 receptor were detected at 50 kDa and 44 kDa. LPA-induced contraction was almost completely blocked by LPA receptor (1/3) antagonist KI16425. Pertussis toxin (PTX) inhibited the contraction induced by LPA, suggesting that the contraction is mediated by a PTX-sensitive G protein. Phospholipase C (PLC) inhibitors U73122 and neomycin, and protein kinase C (PKC) inhibitor GF109203X also reduced the contraction. The PKC-mediated contraction may be isozyme-specific since only PKCε antibody inhibited the contraction. MEK inhibitor PD98059 and JNK inhibitor SP600125 blocked the contraction. However, there is no synergistic effect of PKC and MAPK on the LPA-induced contraction. In addition, RhoA inhibitor C3 exoenzyme and ROCK inhibitor Y27632 significantly, but not completely, reduced the contraction. The present study demonstrated that LPA-induced contraction seems to be mediated by LPA receptors (1/3), coupled to PTX-sensitive G protein, resulting in activation of PLC, PKC-ε pathway, which subsequently mediates activation of ERK and JNK. The data also suggest that RhoA/ROCK are involved in the LPA-induced contraction.

Protective effect of extract from Rumex aquaticus herba on ethanol-induced gastric damage in rats.

BACKGROUND/AIMS: In this study, we investigated the gastroprotective effect of extract including quercetin-3-O-ß-D-glucuronopyranoside (EIQ) from Rumex aquaticus herba against the ethanol-induced gastric damage in rats. METHODS: The rats were divided into eight groups composed of a non-ethanol group, only EIQ (10 mg/kg) group, groups with absolute ethanol after pretreatment with various doses of EIQ (1, 3 and 10 mg/kg), rebamipide (10 mg/kg), stillen (40 mg/kg) and a control receiving only absolute ethanol. Ethanol-induced gastric lesions, lipid peroxidation, neutrophil infiltration and glutathione level were measured. Superoxide dismutase (SOD) and catalase activity were assessed by an assay kit. Protein expression of SOD, catalase or hemoxygenase-1 (HO-1) was assessed by western blotting analysis. RESULTS AND CONCLUSION: In the absolute ethanol treated group, gastric lesion and malondialdehyde levels were significantly increased with enhanced myeloperoxidase activity. Administration of EIQ 1 h prior to ethanol treatment significantly inhibited the formation of gastric lesions and the elevation of the malondialdehyde levels with myeloperoxidase activity. In addition, pretreatment with EIQ significantly increased the level of glutathione, and elevated the activity and protein expression of radical scavenging enzymes, such as SOD, catalase and HO-1. EIQ may exert anti-inflammatory and anti-oxidative effects against ethanol-induced gastric injury through the reduction of lipid peroxidation, myeloperoxidase activity and free radicals.

Regulation of lysophosphatidic acid-induced COX-2 expression by ERK1/2 activation in cultured feline esophageal epithelial cells.

Lysophosphatidic acid (LPA), a potent bioactive phospholipid, mediates diverse cellular responses by binding to specific G protein-coupled receptors (GPCRs). We investigated the signaling mechanisms underlying LPA-induced COX-2 expression in primary cultures of feline esophageal epithelial cells. The identity of the cultures was confirmed by immunocytochemistry using a cytokeratin antibody. Western blot analysis revealed a concentration-and time-dependent induction of COX-2 in response to LPA. Of the three major MAPKs, only ERK1/2 was activated by LPA in a time-dependent manner. LPA-induced COX-2 expression was significantly attenuated by the MEK inhibitor, PD98059, but not by the JNK inhibitor, SP600125, or the p38 MAPK inhibitor, SB212090. LPA-induced COX-2 expression was repressed by pertussis toxin, GF109204X, and Ki16425, indicating the involvements of PTX-sensitive G(i/o) protein, PKC, and the LPA(1/3) receptor, respectively. Our data suggest that in esophageal epithelial cells, LPA-induced COX-2 expression requires activation of PKC and ERK1/2 downstream of the LPA(1/3) receptor, Understanding the regulation of COX-2 expression induced by LPA in esophageal epithelial cells might provide a new therapeutic strategy for esophageal inflammatory diseases.