Intracellular heat shock protein-70 negatively regulates TLR4 signaling in the newborn intestinal epithelium.
Intracellular heat shock protein-70 negatively regulates TLR4 signaling in the newborn intestinal epithelium.
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DOI：
10.4049/jimmunol.1103114
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发表时间：
2012-05-01
期刊：
影响因子：
--
通讯作者：
Hackam DJ
中科院分区：
文献类型：
--
作者：
Afrazi A;Sodhi CP;Good M;Jia H;Siggers R;Yazji I;Ma C;Neal MD;Prindle T;Grant ZS;Branca MF;Ozolek J;Chang EB;Hackam DJ
坏死性小肠结肠炎（NEC）是早产儿胃肠道相关死亡的主要原因，在新生儿肠上皮中toll样受体-4 （TLR4）信号过度的条件下发展。由于尽管存在肠道TLR4的强直性刺激，NEC并不会自发发展，因此我们假设一定存在抑制在NEC发病过程中减弱的TLR4信号的机制，并将重点放在细胞内应激反应蛋白和伴侣热休克蛋白-70 （Hsp70）上。我们现在证明，通过lps诱导的NFkB易位、细胞因子表达和凋亡，肠细胞内Hsp70的诱导显著降低了TLR4信号转导。这些发现在体内得到了证实，使用的小鼠要么整体缺乏Hsp70，要么在肠上皮内过度表达Hsp70。TLR4激活本身显著增加了肠细胞中Hsp70的表达，提供了TLR4信号在肠细胞中的自抑制机制。为了确定其中的机制，细胞内hsp70介导的TLR4信号抑制需要其底物结合eevd结构域和与共伴侣CHIP的关联，从而导致TLR4的泛素化和蛋白体降解。与健康对照组相比，小鼠和人NEC肠上皮中Hsp70的表达显著降低，提示TLR4对Hsp70的保护作用丧失可能导致NEC。小鼠肠道Hsp70过表达和药理学上调Hsp70可逆转tlr4诱导的细胞因子和肠细胞凋亡，预防和治疗实验性NEC。因此，新生儿肠道中存在一种新的TLR4调控途径，涉及Hsp70，可以通过药理激活来限制NEC的严重程度。
Necrotizing enterocolitis (NEC) is the leading cause of gastrointestinal-related mortality in premature infants, and develops under conditions of exaggerated Toll-like receptor-4 (TLR4) signaling in the newborn intestinal epithelium. Since NEC does not develop spontaneously despite the presence of seemingly tonic stimulation of intestinal TLR4, we hypothesized that mechanisms must exist to constrain TLR4 signaling that become diminished during NEC pathogenesis, and focused on the intracellular stress response protein and chaperone Heat Shock Protein-70 (Hsp70). We now demonstrate that the induction of intracellular Hsp70 in enterocytes dramatically reduced TLR4 signaling as assessed by LPS-induced NFkB translocation, cytokine expression and apoptosis. These findings were confirmed in vivo, using mice that either globally lacked Hsp70 or which over-expressed Hsp70 within the intestinal epithelium. TLR4 activation itself significantly increased Hsp70 expression in enterocytes, which provided a mechanism of auto-inhibition of TLR4 signaling in enterocytes. In seeking to define the mechanisms involved, intracellular Hsp70-mediated inhibition of TLR4 signaling required both its substrate-binding EEVD-domain and association with the co-chaperone CHIP, resulting in ubiquitination and proteosomal degradation of TLR4. The expression of Hsp70 in the intestinal epithelium was significantly decreased in murine and human NEC compared to healthy controls, suggesting loss of Hsp70 protection from TLR4 could lead to NEC. In support of this, intestinal-Hsp70 overexpression in mice and pharmacologic upregulation of Hsp70 reversed TLR4-induced cytokines and enterocyte apoptosis, and prevented and treated experimental NEC. Thus, a novel TLR4 regulatory pathway exists within the newborn gut involving Hsp70 that may be pharmacologically activated to limit NEC severity.
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影响因子：
3.6
作者：
Afrazi A;Sodhi CP;Richardson W;Neal M;Good M;Siggers R;Hackam DJ
通讯作者：
Hackam DJ
DOI：
10.1152/ajpgi.00328.2004
发表时间：
2005-05-01
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作者：
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作者：
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