Department of Pediatric Surgery, University Hospital of Leipzig, Leipzig, Germany.
PLoS One. 2012;7(7):e41026. doi: 10.1371/journal.pone.0041026. Epub 2012 Jul 13.
Incidence of urinary tract infections is elevated in patients with diabetes mellitus. Those patients show increased levels of the saturated free fatty acid palmitate. As recently shown metabolic alterations induced by palmitate include production and secretion of the pro-inflammatory cytokine interleukine-6 (IL-6) in cultured human bladder smooth muscle cells (hBSMC). Here we studied the influence of palmitate on vital cell properties, for example, regulation of cell proliferation, mitochondrial enzyme activity and antioxidant capacity in hBSMC, and analyzed the involvement of major cytokine signaling pathways.
METHODOLOGY/PRINCIPAL FINDINGS: HBSMC cultures were set up from bladder tissue of patients undergoing cystectomy and stimulated with palmitate. We analyzed cell proliferation, mitochondrial enzyme activity, and antioxidant capacity by ELISA and confocal immunofluorescence. In signal transduction inhibition experiments we evaluated the involvement of NF-κB, JAK/STAT, MEK1, PI3K, and JNK in major cytokine signaling pathway regulation. We found: (i) palmitate decreased cell proliferation, increased mitochondrial enzyme activity and antioxidant capacity; (ii) direct inhibition of cytokine receptor by AG490 even more strongly suppressed cell proliferation in palmitate-stimulated cells, while counteracting palmitate-induced increase of antioxidant capacity; (iii) in contrast knockdown of the STAT3 inhibitor SOCS3 increased cell proliferation and antioxidant capacity; (iv) further downstream JAK/STAT3 signaling cascade the inhibition of PI3K or JNK enhanced palmitate induced suppression of cell proliferation; (v) increase of mitochondrial enzyme activity by palmitate was enhanced by inhibition of PI3K but counteracted by inhibition of MEK1.
CONCLUSIONS/SIGNIFICANCE: Saturated free fatty acids (e.g., palmitate) cause massive alterations in vital cell functions of cultured hBSMC involving distinct major cytokine signaling pathways. Thereby, certain cytokines might counteract the palmitate-induced downregulation of cell proliferation and vitality. This could be an important link to clinical findings of increased risk of metabolic related bladder diseases such as overactive bladder (OAB) and bladder pain syndrome/interstitial cystitis (BPS/IC).
患有糖尿病的患者尿路感染的发病率升高。这些患者的饱和游离脂肪酸棕榈酸水平升高。最近的研究表明，棕榈酸引起的代谢改变包括在培养的人膀胱平滑肌细胞（hBSMC）中产生和分泌促炎细胞因子白细胞介素-6（IL-6）。在这里，我们研究了棕榈酸对hBSMC 的重要细胞特性的影响，例如细胞增殖、线粒体酶活性和抗氧化能力的调节，并分析了主要细胞因子信号通路的参与情况。
方法/主要发现：从接受膀胱切除术的患者的膀胱组织中建立 hBSMC 培养物，并用棕榈酸刺激。我们通过 ELISA 和共聚焦免疫荧光分析细胞增殖、线粒体酶活性和抗氧化能力。在信号转导抑制实验中，我们评估了 NF-κB、JAK/STAT、MEK1、PI3K 和 JNK 在主要细胞因子信号通路调节中的参与情况。我们发现：（i）棕榈酸降低细胞增殖，增加线粒体酶活性和抗氧化能力；（ii）AG490 直接抑制细胞因子受体，甚至更强烈地抑制棕榈酸刺激细胞的细胞增殖，同时抵消棕榈酸诱导的抗氧化能力增加；（iii）相反，STAT3 抑制剂 SOCS3 的敲低增加了细胞增殖和抗氧化能力；（iv）在 JAK/STAT3 信号级联的下游，PI3K 或 JNK 的抑制增强了棕榈酸诱导的细胞增殖抑制；（v）棕榈酸增加线粒体酶活性的作用通过 PI3K 的抑制增强，但通过 MEK1 的抑制抵消。
结论/意义：饱和游离脂肪酸（例如棕榈酸）导致培养的 hBSMC 的重要细胞功能发生巨大变化，涉及不同的主要细胞因子信号通路。因此，某些细胞因子可能会抵消棕榈酸诱导的细胞增殖和活力下降。这可能是与代谢相关的膀胱疾病（如膀胱过度活动症（OAB）和膀胱疼痛综合征/间质性膀胱炎（BPS/IC））的临床发现中风险增加的重要联系。
