Dexmedetomidine alleviates LPS-induced septic cardiomyopathy via the cholinergic anti-inflammatory pathway in mice

Abstract

This study was conducted to investigate the role of the cholinergic anti-inflammatory pathway in LPS-induced septic cardiomyopathy in mice. C57BL/6 mice were used to construct septic cardiomyopathy models. The optimal duration of lipopolysaccharide (LPS) treatment was determined by HE staining and TUNEL assay. Blank controls were intraperitoneally injected with saline and models were injected with LPS (10 mg/kg) (LPS), α-bungarotoxin (BT-LPS), BT and dexmedetomidine (BT-DEX-LPS). The pathological examinations were performed on HE- stained myocardium tissues, apoptosis was determined using TUNEL assay, mRNA expression of NF-κB p65, Caspase-3, Caspase-8, Bcl-2, Bax, p53 and α7nACh was quantified using qRT-PCR, protein levels of IL-6, IL-1β, TNF-α and phosphorylated STAT3 (p-STAT3) were analyzed using Western blot analysis. HE staining and TUNEL assays showed that the optimal LPS treatment time for septic cardiomyopathy induction was 16 h. Compared with the blank control, mice in LPS group had significantly higher apoptosis, while DEX and BT reduced apoptosis when they were used separately and increased apoptosis when they were used jointly. In the LPS-treated mice, the levels of NF-κb p65, Caspase-3, Caspase-8, Bax, p53, IL-6, IL-1β, TNF-α and p-STAT3 were significantly increased, while α7nAChR level was decreased significantly (P < 0.01); DEX alone had no impact on the expression of these proteins but significantly up-regulated the expression of these genes except α7nAChR when used jointly with BT (P < 0.01). It is clear that DEX can alleviate heart injury, while α7nAChR-specific blocker BT is antagonistic against the anti-inflammatory effect of DEX on sepsis in mice.

Keywords: Cardiomyopathy; apoptosis; gene expression; sepsis.

Figure 1

HE staining and TUNEL results of heart tissues following LPS treatments for different times (100×). A. HE staining, showing deformation of muscles and leaking of red blood cells. B. TUNEL assay showing increased number of apoptotic cells following LPS treatment.

Figure 2

HE staining and TUNEL results of heart tissues following different drug treatments (200×). A. HE staining showing deformation of muscles and leaking of red blood cells. B. TUNEL assay showing apoptotic cells following various treatments.

Figure 3

Relative mRNA level of NF-κB, a7nAChR, Caspase-3, Caspase-8, Bcl-2, Bax and p53 mRNA in cardiac tissue following DEX, BT and LPS treatments. A. NF-κB and a7nAChR expression; B. Caspase-3, Caspase-8, Bcl-2, Bax and p53 expression. ***denote P < 0.01 vs control.

Figure 4

Expression of IL-6, IL-1, TNF- and p-STAT3 proteins in cardiac tissue following DEX, BT and LPS treatments. Left panel: representative Western blots, right panel: relative protein levels. ***denote P < 0.01 vs control.