Amphetamine activates connexin43 gene expression in cultured neonatal rat cardiomyocytes through JNK and AP-1 pathway

Abstract

Objective: Amphetamine has been known to induce cardiac dysrhythmia and sudden death. However, the molecular mechanism for the induction of dysrhythmia is not known. Connexin43 (Cx43) plays an important role for arrhythmogenesis. This study was undertaken to test the hypothesis that amphetamine could induce Cx43 expression in cardiac myocytes. Methods: Neonatal Wistar rat cardiac myocytes were cultured under the stimulation of amphetamine. Cx43 mRNA and protein expression were examined by Northern and Western blots, respectively. We used c-Jun N-terminal kinase (JNK) inhibitor, SP600125, and JNK1 dsRNAi to investigate the signal pathway of amphetamine-induced expression of Cx43. Results: The level of Cx43 protein significantly increased from 4 to 24 h after addition of amphetamine (10 AM). The Cx43 mRNA increased maximally to 4.2-fold at 6 h after addition of amphetamine and returned to the baseline level at 48 h. These increases of Cx43 protein at 24 h were completely attenuated ( P < 0.001) by SP600125 (20 AM) and JNK1 dsRNAi. Amphetamine increased and SP600125 decreased the immunohistochemical labeling of Cx43. Amphetamine increased and SP600125 decreased the phosphorylated JNK and c-Jun proteins. Gel-shifting assay showed that DNA-binding activity of AP-1 increased after addition of amphetamine and SP600125 and JNK1 dsRNAi abolished the binding activity induced by amphetamine. Conclusions: These findings indicate that amphetamine activates Cx43 gene expression in cultured rat neonatal cardiac myocytes. Amphetamine mediates the Cx43 gene expression, at least in part, through the JNK pathway. These findings from our study suggest that Cx43 plays a role for the molecular mechanism of amphetamine-induced cardiac dysrhythmias.

Involvement of connexin 43 in angiotensin II-induced migration and proliferation of saphenous vein smooth muscle cells via the MAPK-AP-1 signaling pathway

“…However, many of the signaling events relevant to cell proliferation and differentiation are mediated through activation of transcription factors via MAP kinases, which can be upregulated by Ang II [36]. Activation of the ERK, p38 and JNK signaling pathways may participate in the regulation of cardiac gap junctions [25,37]. Here, our results confirm that Ang II can modulate the expression of Cx43 via the ERK1/2, p38 MAPK and JNK in hSV SMCs.…”

“…Dominant-negative AP-1 (A-Fos) has been proven to inhibit AP-1 activity in epithelial tumor cell [39] and cardiac cells [40]. In cultured neonatal rat cardiomyocytes, amphetamineactivated Cx43 gene expression was through the JNK and AP-1 pathways [37]. The AP-1 and its promoter site are likely involved in the cytokine regulation of Cx43 [41].…”

Downregulated myocardial connexin 43 and suppressed contractility in rabbits subjected to a cholesterol-enriched diet

“…19 On the other hand, a wellcharacterized downstream targets of JNK, activating protein 1 is an activator of the Cx43 proximal promoter in several different cell types, including cardiomyocytes. 45 Our study correlated, although with a time lag, the activation of JNK with the upregulation of Cx43 transcripts and downregulation Cx43 proteins. Further studies will be needed to establish the specific mechanisms of hypercholesterolemia-mediated Cx43 downregulation, including alterations in Cx43 protein synthesis, degradation and membrane assembly.…”

Angiotensin II activates myostatin expression in cultured rat neonatal cardiomyocytes via p38 MAP kinase and myocyte enhance factor 2 pathway

“…Western blot was performed as previously described (Shyu et al 2004). Rabbit polyclonal anti-myostatin antibody (Chemicon, Temecula, CA, USA), polyclonal anti-p38 MAP kinase, monoclonal anti-phospho p38 MAP kinase antibodies (Cell Signaling, Beverly, MA, USA), goat polyclonal antibody against total MEF-2 (Santa Cruz Biotechnol Inc., Santa Cruz, CA, USA), and rabbit polyclonal antibody against phosphorylated MEF-2 (Santa Cruz Biotechnol Inc.) were used.…”