Dong Maolong, Hu Nan, Hua Yinan, Xu Xihui, Kandadi Machender R, Guo Rui, Jiang Shasha, Nair Sreejayan, Hu Dahai, Ren Jun
Department of Burn and Cutaneous Surgery, Xijing Hospital, the Fourth Military Medical University, Xi'an 710032, PR China.
Biochim Biophys Acta. 2013 Jun;1832(6):848-63. doi: 10.1016/j.bbadis.2013.02.023. Epub 2013 Mar 6.
Sepsis is characterized by systematic inflammation and contributes to cardiac dysfunction. This study was designed to examine the effect of protein kinase B (Akt) activation on lipopolysaccharide-induced cardiac anomalies and underlying mechanism(s) involved. Mechanical and intracellular Ca²⁺ properties were examined in myocardium from wild-type and transgenic mice with cardiac-specific chronic Akt overexpression following LPS (4 mg/kg, i.p.) challenge. Akt signaling cascade (Akt, phosphatase and tensin homologue deleted on chromosome ten, glycogen synthase kinase 3 beta), stress signal (extracellular-signal-regulated kinases, c-Jun N-terminal kinases, p38), apoptotic markers (Bcl-2 associated X protein, caspase-3/-9), endoplasmic reticulum (ER) stress markers (glucose-regulated protein 78, growth arrest and DNA damage induced gene-153, eukaryotic initiation factor 2α), inflammatory markers (tumor necrosis factor α, interleukin-1β, interleukin-6) and autophagic markers (Beclin-1, light chain 3B, autophagy-related gene 7 and sequestosome 1) were evaluated. Our results revealed that LPS induced marked decrease in ejection fraction, fractional shortening, cardiomyocyte contractile capacity with dampened intracellular Ca²⁺ release and clearance, elevated reactive oxygen species (ROS) generation and decreased glutathione and glutathione disulfide (GSH/GSSG) ratio, increased ERK, JNK, p38, GRP78, Gadd153, eIF2α, BAX, caspase-3 and -9, downregulated B cell lymphoma 2 (Bcl-2), the effects of which were significantly attenuated or obliterated by Akt activation. Akt activation itself did not affect cardiac contractile and intracellular Ca²⁺ properties, ROS production, oxidative stress, apoptosis and ER stress. In addition, LPS upregulated levels of Beclin-1, LC3B and Atg7, while suppressing p62 accumulation. Akt activation did not affect Beclin-1, LC3B, Atg7 and p62 in the presence or absence of LPS. Akt overexpression promoted phosphorylation of Akt and GSK3β. In vitro study using the GSK3β inhibitor SB216763 mimicked the response elicited by chronic Akt activation. Taken together, these data showed that Akt activation ameliorated LPS-induced cardiac contractile and intracellular Ca²⁺ anomalies through inhibition of apoptosis and ER stress, possibly involving an Akt/GSK3β-dependent mechanism.
脓毒症的特征是全身性炎症，并会导致心脏功能障碍。本研究旨在检测蛋白激酶B（Akt）激活对脂多糖诱导的心脏异常及相关潜在机制的影响。在腹腔注射脂多糖（4 mg/kg）刺激后，检测野生型小鼠和心脏特异性慢性Akt过表达转基因小鼠心肌的机械特性和细胞内钙离子特性。评估Akt信号级联反应（Akt、10号染色体上缺失的磷酸酶和张力蛋白同源物、糖原合酶激酶3β）、应激信号（细胞外信号调节激酶、c-Jun氨基末端激酶、p38）、凋亡标志物（Bcl-2相关X蛋白、半胱天冬酶-3/-9）、内质网（ER）应激标志物（葡萄糖调节蛋白78、生长停滞和DNA损伤诱导基因-153、真核起始因子2α）、炎症标志物（肿瘤坏死因子α、白细胞介素-1β、白细胞介素-6）和自噬标志物（Beclin-1、轻链3B、自噬相关基因7和聚集体蛋白1）。我们的结果显示，脂多糖导致射血分数、缩短分数、心肌细胞收缩能力显著降低，细胞内钙离子释放和清除受到抑制，活性氧（ROS）生成增加，谷胱甘肽和谷胱甘肽二硫化物（GSH/GSSG）比值降低，细胞外信号调节激酶、c-Jun氨基末端激酶、p38、葡萄糖调节蛋白78、生长停滞和DNA损伤诱导基因-153、真核起始因子2α、BAX、半胱天冬酶-3和-9升高，B细胞淋巴瘤2（Bcl-2）下调，而Akt激活可显著减轻或消除这些影响。Akt激活本身并不影响心脏收缩和细胞内钙离子特性、ROS产生、氧化应激、细胞凋亡和内质网应激。此外，脂多糖上调Beclin-1、轻链3B和自噬相关基因7的水平，并抑制聚集体蛋白1的积累。无论有无脂多糖存在，Akt激活均不影响Beclin-1、轻链3B、自噬相关基因7和聚集体蛋白1。Akt过表达促进Akt和糖原合酶激酶3β的磷酸化。使用糖原合酶激酶3β抑制剂SB216763的体外研究模拟了慢性Akt激活引发的反应。综上所述，这些数据表明，Akt激活通过抑制细胞凋亡和内质网应激改善脂多糖诱导的心脏收缩和细胞内钙离子异常，可能涉及Akt/糖原合酶激酶3β依赖性机制。
