Inhibition of angiotensin converting enzyme increases PKCβI isoform expression via activation of substance P and bradykinin receptors in cultured astrocytes of mice

Background@#Angiotensin-converting enzyme inhibitor (ACEi) inhibits the catalysis of angiotensin I to angiotensin II and the degradation of substance P (SP) and bradykinin (BK). While the possible relationship between ACEi and SP in nociceptive mice was recently suggested, the effect of ACEi on signal transduction in astrocytes remains unclear. @*Objectives@#This study examined whether ACE inhibition with captopril or enalapril modulates the levels of SP and BK in primary cultured astrocytes and whether this change modulates PKC isoforms (PKCα, PKCβI, and PKCε) expression in cultured astrocytes. @*Methods@#Immunocytochemistry and Western blot analysis were performed to examine the changes in the levels of SP and BK and the expression of the PKC isoforms in primary cultured astrocytes, respectively. @*Results@#The treatment of captopril or enalapril increased the immunoreactivity of SP and BK significantly in glial fibrillary acidic protein-positive cultured astrocytes. These increases were suppressed by a pretreatment with an angiotensin-converting enzyme.In addition, treatment with captopril increased the expression of the PKCβI isoform in cultured astrocytes, while there were no changes in the expression of the PKCα and PKCε isoforms after the captopril treatment. The captopril-induced increased expression of the PKCβI isoform was inhibited by a pretreatment with the neurokinin-1 receptor antagonist, L-733,060, the BK B 1 receptor antagonist, R 715, or the BK B 2 receptor antagonist, HOE 140. @*Conclusions@#These results suggest that ACE inhibition with captopril or enalapril increases the levels of SP and BK in cultured astrocytes and that the activation of SP and BK receptors mediates the captopril-induced increase in the expression of the PKCβI isoform.

NAG-1/GDF-15 Transgenic Female Mouse Shows Delayed Peak Period of the Second Phase Nociception in Formalin-induced Inflammatory Pain

Non-steroidal anti-inflammatory drug-activated gene-1 (NAG-1), also known as growth differentiation factor-15 (GDF-15), is associated with cancer, diabetes, and inflammation, while there is limited understanding of the role of NAG-1 in nociception. Here, we examined the nociceptive behaviors of NAG-1 transgenic (TG) mice and wild-type (WT) littermates. Mechanical sensitivity was evaluated by using the von Frey filament test, and thermal sensitivity was assessed by the hot-plate, Hargreaves, and acetone tests. c-Fos, glial fibrillary acidic protein (GFAP), and ionized calcium binding adaptor molecule-1 (Iba-1) immunoreactivity was examined in the spinal cord following observation of the formalin-induced nociceptive behaviors. There was no difference in mechanical or thermal sensitivity for NAG-1 TG and WT mice. Intraplantar formalin injection induced nociceptive behaviors in both male and female NAG-1 TG and WT mice. The peak period in the second phase was delayed in NAG-1 TG female mice compared with that of WT female mice, while there was no difference in the cumulative time of nociceptive behaviors between the two groups of mice. Formalin increased spinal c-Fos immunoreactivity in both TG and WT female mice. Neither GFAP nor Iba-1 immunoreactivity was increased in the spinal cord of TG and WT female mice. These findings indicate that NAG-1 TG mice have comparable baseline sensitivity to mechanical and thermal stimulation as WT mice and that NAG-1 in female mice may have an inhibitory effect on the second phase of inflammatory pain. Therefore, it could be a novel target to inhibit central nervous system response in pain.

Spinal Nitric Oxide Synthase Type II Increases Neurosteroid-metabolizing Cytochrome P450c17 Expression in a Rodent Model of Neuropathic Pain

We have previously demonstrated that the neurosteroid dehydroepiandrosterone sulfate (DHEAS) induces functional potentiation of N-methyl-D-aspartate (NMDA) receptors via increases in phosphorylation of NMDA receptor GluN1 subunit (pGluN1). However, the modulatory mechanisms responsible for the expression of the DHEA-synthesizing enzyme, cytochrome P450c17 following peripheral nerve injury have yet to be examined. Here we determined whether oxidative stress induced by the spinal activation of nitric oxide synthase type II (NOS-II) modulates the expression of P450c17 and whether this process contributes to the development of neuropathic pain in rats. Chronic constriction injury (CCI) of the sciatic nerve induced a significant increase in the expression of NOS-II in microglial cells and NO levels in the lumbar spinal cord dorsal horn at postoperative day 5. Intrathecal administration of the NOS-II inhibitor, L-NIL during the induction phase of neuropathic pain (postoperative days 0~5) significantly reduced the CCI-induced development of mechanical allodynia and thermal hyperalgesia. Sciatic nerve injury increased the expression of PKC- and PKA-dependent pGluN1 as well as the mRNA and protein levels of P450c17 in the spinal cord at postoperative day 5, and these increases were suppressed by repeated administration of L-NIL. Co-administration of DHEAS together with L-NIL restored the development of neuropathic pain and pGluN1 that were originally inhibited by L-NIL administration alone. Collectively these results provide strong support for the hypothesis that activation of NOS-II increases the mRNA and protein levels of P450c17 in the spinal cord, ultimately leading to the development of central sensitization and neuropathic pain induced by peripheral nerve injury.

Bee venom stimulation of a lung meridian acupoint reduces inflammation in carrageenan-induced pleurisy: an alternative therapeutic approach for respiratory inflammation

Respiratory inflammation is a frequent and fatal pathologic state encountered in veterinary medicine. Although diluted bee venom (dBV) has potent anti-inflammatory effects, the clinical use of dBV is limited to several chronic inflammatory diseases. The present study was designed to propose an acupoint dBV treatment as a novel therapeutic strategy for respiratory inflammatory disease. Experimental pleurisy was induced by injection of carrageenan into the left pleural space in mouse. The dBV was injected into a specific lung meridian acupoint (LU-5) or into an arbitrary non-acupoint located near the midline of the back in mouse. The inflammatory responses were evaluated by analyzing inflammatory indicators in pleural exudate. The dBV injection into the LU-5 acupoint significantly suppressed the carrageenan-induced increase of pleural exudate volume, leukocyte accumulation, and myeloperoxidase activity. Moreover, dBV acupoint treatment effectively inhibited the production of interleukin 1 beta, but not tumor necrosis factor alpha in the pleural exudate. On the other hand, dBV treatment at non-acupoint did not inhibit the inflammatory responses in carrageenan-induced pleurisy. The present results demonstrate that dBV stimulation in the LU-5 lung meridian acupoint can produce significant anti-inflammatory effects on carrageenan-induced pleurisy suggesting that dBV acupuncture may be a promising alternative medicine therapy for respiratory inflammatory diseases.