The role of β-adrenergic receptors and p38MAPK signaling pathways in physiological processes of cardiosphere-derived cells

SK4 calcium-activated potassium channels activated by sympathetic nerves enhances atrial fibrillation vulnerability in a canine model of acute stroke

Background

New-onset atrial fibrillation (AF) is common in patients with acute stroke (AS). Studies have shown that intermediate-conductance calcium-activated potassium channel channels (SK4) play an important role in cardiomyocyte automaticity. The aim of this study was to investigate the effects of SK4 on AF vulnerability in dogs with AS.

Experimental

Eighteen dogs were randomly divided into a control group, AS group and left stellate ganglion ablation (LSGA) group. In the control group, dogs received craniotomy without right middle cerebral artery occlusion (MCAO). AS dogs were established using a cerebral ischemic model with right MCAO. LSGA dogs underwent MCAO, and LSGA was performed.

Results

Three days later, the dispersion of the effective refractory period (dERP) and AF vulnerability in the AS group were significantly increased compared with those in the control group and LSGA group. However, no significant difference in dERP and AF vulnerability was found between the control group and the LSGA group. The SK4 inhibitor (TRAM-34) completely inhibited the inducibility of AF in AS dogs. SK4 expression and levels of noradrenaline (NE), β1-AR, p38 and c-Fos in the atrium were higher in the AS dogs than in the control group or LSGA group. However, no significant difference in SK4 expression or levels of NE, β1-AR, p38 and c-Fos in the left atrium was observed between the control group and LSGA group.

Conclusion

SK4 plays a key role in AF vulnerability in a canine model with AS. The effects of LSGA on AF vulnerability were associated with the p38 signaling pathways.

Ganoderic acid A protects neural cells against NO stress injury in vitro via stimulating β adrenergic receptors

Excessive nitric oxide (NO) causes extensive damage to the nervous system, and the adrenergic system is disordered in many neuropsychiatric diseases. However, the role of the adrenergic system in protection of the nervous system against sodium nitroprusside (SNP) injury remains unclear. In this study, we investigated the effect of ganoderic acid A (GA A) against SNP injury in neural cells and the role of adrenergic receptors in GA A neuroprotection. We found that SNP (0.125-2 mM) dose-dependently decreased the viability of both SH-SY5Y and PC12 cells and markedly increased NO contents. Pretreatment with GA A (10 μM) significantly attenuated SNP-induced cytotoxicity and NO increase in SH-SY5Y cells, but not in PC12 cells. Furthermore, pretreatment with GA A caused significantly higher adrenaline content in SH-SY5Y cells than in PC12 cells. In order to elucidate the mechanism of GA A-protecting SH-SY5Y cells, we added adrenaline, phentolamine, metoprolol, or ICI 118551 1 h before GA A was added to the culture medium. We found that addition of adrenaline (10 μM) significantly improved GA A protection in PC12 cells. The addition of β1-adrenergic receptor antagonist metoprolol (10 μM) or β2-adrenergic receptor antagonist ICI 118551 (0.1 μM) blocked the protective effect of GA A, whereas the addition of α-adrenergic receptor antagonist phentolamine (0.1 μM) did not affect GA A protection in SH-SY5Y cells. These results suggest that β-adrenergic receptors play an important role in the protection of GA A in SH-SY5Y cells against SNP injuries, and excessive adrenaline system activation caused great damage to the nervous system.

N‑acetyl cysteine inhibits lipopolysaccharide‑induced apoptosis of human umbilical vein endothelial cells via the p38MAPK signaling pathway

Lipopolysaccharide (LPS) can regulate the expression of apoptotic factors, including caspase‑3, Bcl‑2 and Bcl‑2‑associated X protein (Bax). Nitric oxide (NO) plays an important role in apoptosis. N‑acetyl cysteine (NAC) has been shown to exhibit antioxidant effects in vitro. However, the effects of NAC on LPS‑induced apoptosis of human umbilical vein endothelial cells (HUVECs) and the associated mechanisms are not well characterized. The present study explored the effect of NAC on LPS‑induced apoptosis of HUVECs and determined the participation of the p38 mitogen‑activated protein kinase (MAPK) pathway in the process of apoptosis. Cell viability was assessed using the Cell Counting Kit‑8 (CCK‑8) assay. The expression of caspase‑3, Bax, Bcl‑2, phosphorylated (p)‑p38MAPK/total (t‑)p38MAPK and p‑endothelial e nitric oxide synthase (eNOS)/t‑eNOS proteins were determined by western blotting. The expression levels of caspase‑3, Bax and Bcl‑2 mRNA were determined using reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). The rate of apoptosis was determined using flow cytometry. An NO detection kit (nitric reductase method) was used to determine NO concentration. The results of CCK‑8 and flow cytometric analyses showed that pretreatment of HUVECs with NAC or p38MAPK inhibitor (SB203580) attenuated LPS‑induced decrease in cell viability and increase in cell apoptosis. RT‑qPCR and western blotting showed that LPS promoted caspase‑3 and Bax expression, but inhibited that of Bcl‑2 in HUVECs; however, these effects were attenuated by pretreatment with NAC or SB203580. LPS stimulation significantly enhanced the expression of p‑p38MAPK protein and reduced the expression of p‑eNOS protein; however, these effects were attenuated by pretreatment with NAC or SB203580. NAC pretreatment attenuated LPS‑induced inhibition of NO synthesis, which was consistent with the effects of SB203580. The results demonstrated that NAC pretreatment alleviated LPS‑induced apoptosis and inhibition of NO production in HUVECs. Furthermore, these effects were proposed to be mediated via the p38MAPK signaling pathway.

β-adrenergic receptors and cardiac progenitor cell biology: What is the real connection?

Resident cardiac progenitor cells (CPCs) isolated from small animal models may not always be representative of their human counterparts, especially when significant differences in isolation protocols are considered. Nonetheless, multiple evidences support an important role of β-adrenergic signaling in human CPC survival and commitment, which will need appropriate consideration for future developments of human CPCs as regenerative medicine tools.