Nefrología, IIS-Fundación Jiménez Diaz, Madrid, Spain.
Lab Invest. 2012 Jan;92(1):32-45. doi: 10.1038/labinvest.2011.138. Epub 2011 Sep 19.
Apoptosis is a driving force of diabetic end-organ damage, including diabetic nephropathy (DN). However, the mechanisms that modulate diabetes-induced cell death are not fully understood. Heat shock protein 27 (HSP27/HSPB1) is a cell stress protein that regulates apoptosis in extrarenal cells and is expressed by podocytes exposed to toxins causing nephrotic syndrome. We investigated the regulation of HSPB1 expression and its function in podocytes exposed to factors contributing to DN, such as high glucose and angiotensin (Ang) II. HSPB1 expression was assessed in renal biopsies from patients with DN, minimal change disease or focal segmental glomerulosclerosis (FSGS), in a rat model of diabetes induced by streptozotocin (STZ) and in Ang II-infused rats. The regulation of HSPB1 was studied in cultured human podocytes and the function of HSPB1 expressed in response to pathophysiologically relevant stimuli was explored by short interfering RNA knockdown. Total kidney HSPB1 mRNA and protein expression was increased in rats with STZ-induced diabetes and in rats infused with Ang II. Upregulation of HSPB1 protein was confirmed in isolated diabetic glomeruli. Immunohistochemistry showed increased glomerular expression of HSPB1 in both models and localized glomerular HSPB1 to podocytes. HSPB1 protein was increased in glomerular podocytes from patients with DN or FSGS. In cultured human podocytes HSPB1 mRNA and protein expression was upregulated by high glucose concentrations and Ang II. High glucose, but not Ang II, promoted podocyte apoptosis. HSPB1 short interfering RNA (siRNA) targeting increased apoptosis in a high-glucose milieu and sensitized to Ang II or TGFβ1-induced apoptosis by promoting caspase activation. In conclusion, both high glucose and Ang II contribute to HSPB1 upregulation. HSPB1 upregulation allows podocytes to better withstand an adverse high-glucose or Ang II-rich environment, such as can be found in DN.
细胞凋亡是糖尿病终末器官损伤（包括糖尿病肾病）的驱动因素。然而，调节糖尿病诱导的细胞死亡的机制尚未完全阐明。热休克蛋白 27（HSP27/HSPB1）是一种细胞应激蛋白，可调节肾脏以外细胞的细胞凋亡，并在暴露于引起肾病综合征的毒素的足细胞中表达。我们研究了 HSPB1 表达的调节及其在暴露于高血糖和血管紧张素（Ang）II 等导致糖尿病肾病的因素的足细胞中的功能。在糖尿病肾病、微小病变性肾病或局灶节段性肾小球硬化症患者的肾活检组织中，在链脲佐菌素（STZ）诱导的糖尿病大鼠模型中和在 Ang II 输注大鼠中评估了 HSPB1 表达。在培养的人足细胞中研究了 HSPB1 的调节，并用短干扰 RNA 敲低研究了对病理生理相关刺激表达的 HSPB1 的功能。STZ 诱导的糖尿病大鼠和 Ang II 输注大鼠的总肾脏 HSPB1 mRNA 和蛋白表达增加。在两种模型中均证实 HSPB1 蛋白表达增加，并将 HSPB1 定位于肾小球。免疫组化显示两种模型中 HSPB1 在肾小球的表达均增加，并将 HSPB1 定位在足细胞。糖尿病肾病或局灶节段性肾小球硬化症患者的肾小球足细胞中 HSPB1 蛋白表达增加。在培养的人足细胞中，高葡萄糖浓度和 Ang II 上调 HSPB1 mRNA 和蛋白表达。高葡萄糖但不是 Ang II 促进足细胞凋亡。针对 HSPB1 的 siRNA 靶向增加高葡萄糖环境中的细胞凋亡，并通过促进半胱天冬酶激活使足细胞对 Ang II 或 TGFβ1 诱导的凋亡更加敏感。总之，高葡萄糖和 Ang II 均有助于 HSPB1 上调。HSPB1 的上调使足细胞能够更好地耐受高葡萄糖或富含 Ang II 的不利环境，如糖尿病肾病中所见。
