Activation Of Alpha7 Nicotinic Acetylcholine Receptors Research Articles

Alpha7 nicotinic acetylcholine receptor activation protects against myocardial reperfusion injury through modulation of autophagy

Alpha7 nicotinic acetylcholine receptor (α7nAChR) activation alleviates myocardial ischemia/reperfusion (MI/R) injury. However, the underlying mechanisms remain unclear. Here, we investigated the role of autophagy in α7nAChR-mediated cardioprotection and the molecular mechanisms involved. Activating α7nAChR with PNU-282987 at the initiation of reperfusion reduced myocardial infarct size in MI/R rats. PNU-282987 treatment also significantly inhibited MI/R-induced myocardial autophagy dysfunction as evidenced by the reduction of LC3-II/LC3-I ratio, Beclin-1 and p62 abundance. In addition, PNU-282987 treatment reduced hypoxia/reoxygenation (H/R)-induced cardiomyocyte injury in vitro, accompanied with the inhibition of Beclin-1-associated autophagy and the restoration of autophagic flux. Interestingly, inhibiting autophagic flux attenuated α7nAChR-afforded improvement of mitochondrial function as well as inhibition of apoptosis in vitro. Mechanistically, co-administration of PNU-282987 with LY294002 (a PI3K inhibitor), AG490 (a JAK2 inhibitor) or Bcl-2 siRNA, but not compound C (an AMPK inhibitor), reduced Bcl-2 level and prevented the modulation of autophagy afforded by PNU-282987 in H/R cardiomyocytes. Collectively, these findings suggest that α7nAChR activation inhibits Beclin-1-associated autophagy dysfunction via the JAK2/Bcl-2 and PI3K/Bcl-2 cascades, leading to cardioprotection against MI/R injury.

Spinal activation of alpha7-nicotinic acetylcholine receptor attenuates posttraumatic stress disorder-related chronic pain via suppression of glial activation

The high prevalence of chronic pain in posttraumatic stress disorder (PTSD) individuals has been widely reported by clinical studies, which emphasized an urgent need to uncover the underlying mechanisms and identify potential therapeutic targets. Recent studies suggested that targeting activated glia and their pro-inflammatory products may provide a novel and effective therapy for the stress-related pain. In this study, we investigated whether activation of alpha-7 nicotinic acetylcholine receptor (α7 nAChR), a novel anti-inflammatory target, could attenuate PTSD-related chronic pain. The experiments were conducted in a rat model of single prolonged stress (SPS), an established model of PTSD-pain comorbidity. We found that SPS exposure produced persistent mechanical allodynia. Immunohistochemical and enzyme-linked immuno sorbent assay analysis showed that SPS also induced elevated activation of glia cells (including microglia and astrocytes) and accumulation of pro-inflammatory cytokines in spinal cord. In another experiment, we found that intrathecal injection of PHA-543613, a selective α7 nAchR agonist, attenuated the SPS-evoked allodynia in a dose dependent manner. However, this anti-hyperalgesic effect was blocked by pretreatment with methyllycaconitine (MLA), a selective α7 nAchR antagonist. Further analyses showed that PHA-543613 suppressed SPS-induced spinal glial activation and SPS-elevated spinal pro-inflammatory cytokines, and these were abolished by MLA. Taken together, the present study showed that spinal activation of α7 nAChR by PHA-543613 attenuated mechanical allodynia induced by PTSD-like stress, and the suppression of spinal glial activation may underlie this anti-hyperalgesic effect. Our study demonstrated the therapeutic potential of targeting α7 nAChR in the treatment of PTSD-related chronic pain.

Alpha7 nicotinic acetylcholine receptor activation attenuated intestine-derived acute lung injury

BackgroundIntestinal ischemia–reperfusion (IIR) could lead to acute lung injury, associated with severe alveolar epithelial cells inflammatory and oxidative injury. Alpha7 nicotinic acetylcholine receptor (α7nAChR) is an essential component of the cholinergic anti-inflammatory pathway. The aim of this study was to investigate the important role of α7nAChR on the lung subjected to IIR. MethodsThirty-two Sprague–Dawley rats were randomly divided into four groups (n = 8 in each): sham group (group S), model group (group M), α7nAChR agonist PNU-282987-treated group (group PNU), and specific α7nAChR antagonist methyllycaconitine-treated group (group MLA). Intestinal IR damage was induced by clamping the superior mesenteric artery for 75 min, followed by a 120-min reperfusion. All rats were killed at 2 h after release of the clamps. The histologic examination of lungs was made, and lung water content was detected. Expression levels of malondialdehyde, tumor necrosis factor alpha, interleukin-6, and superoxide dismutase activity of the lungs were detected. Additionally, expression level of toll-like receptor (TLR)4 and nuclear factor-kappaB (NF-κB p65) in the nucleus of lung tissue and apoptosis-related protein (Bax, Bcl-2, and cleaved-caspase3) were detected using Western blot. ResultsLungs were damaged after intestine IR, manifested by higher lung water content, histologic score, concentrations of interleukin-6, tumor necrosis factor alpha, and malondialdehyde of group M than those of group S, accompanied with decreased superoxide dismutase activity (P < 0.05). PNU treatment could significantly improve the pulmonary function of rats subjected to IIR. These effects of activation of α7nAChR were associated with suppression of TLR4/NF-κB pathway and subsequent reduction of apoptosis-related protein. However, MLA treatment aggravated lung injury. Conclusionsα7nAChR plays a role in acute lung injury induced by IIR via attenuating lung oxidative stress and inflammation through suppression of TLR4/NF-κB pathway, resulting in reduction of apoptosis in the lung.

Abstract 3305: The role of mTOR in mediating nicotine induced alpha-7 nicotinic acetylcholine receptor activation and the regulation of radiotherapeutic response

Abstract Tobacco use is the single largest preventable risk factor for developing cancer. Furthermore, tobacco is associated with poor therapeutic outcomes in part because its continued use has been shown to decrease the efficacy of conventional chemotherapy and/or radiotherapy (RT). Preclinical data suggests that nicotine administration decreases RT efficacy by activating the alpha-7-nicotinic acetylcholine receptor (a7-nAChR). Our study evaluated the effects of nicotine and selective a7-nAChR agonists (LY 2087101, PHA 543613, PNU 282987, and TC 1698) administration on radiotherapeutic efficacy. H460 and A549 human lung cancer cell lines were dose escalated with nicotine and the a7-nAChR agonists alone or in combination with single fraction X-ray radiation (2, 6 Gy) and cell survival was assessed by clonogenic assay. Nicotine administration and activation of a7-nAChR by LY 2087101 or PHA 543613 was found to have a radioprotective effect in both cell lines by increasing cell survival following RT. Conversely, activation of a7-nAChR by PNU 282987 or TC 1698 did not modulate radiotherapeutic response. Western blot analysis demonstrated that although all four tested a7-nAChR agonists increased phosphorylation of AKT (S473), only PHA 543613 and LY 2087101 were found to also activate mTOR (S2448). Additional clonogenic studies were performed to further examine the role of mTORC1 in governing response to RT. Inhibition of mTORC1 by rapamycin alone sensitized both A549 and H460 cells to the effect of RT. Interestingly, rapamycin treatment was sufficient to block the radioprotective effects of nicotine, PHA 543613, and LY 2087101 in A549 cells, however, in H460 cells rapamycin did not restore radiotherapeutic efficacy. Moreover, examination of Deptor, a key component of mTOR complexes shown to be associated with RT response, demonstrated that a7-nAChR activation by nicotine, PHA 543613, or LY 2087101 increased Deptor degradation in A549 cells, while a7-nAChR activation decreased Deptor degradation in H460 cells. These observations suggest that differences in the regulation of Deptor level may contribute to the variation in both rapamycin sensitivity and restoration of therapeutic efficacy to RT between H460 and A549 cell lines. Additional studies will be necessary to further elucidate the role of the mTOR complexes in mediating a7-nAChR induced modulation of response to RT. Citation Format: Samantha L. Sobus, Sundaravadivel Balasubramanian, Michelle A. Romano, Graham W. Warren. The role of mTOR in mediating nicotine induced alpha-7 nicotinic acetylcholine receptor activation and the regulation of radiotherapeutic response. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3305. doi:10.1158/1538-7445.AM2015-3305