A Pathophysiologic Role for Epidermal Growth Factor Receptor in Pemphigus Acantholysis

The pemphigus family of autoimmune bullous disorders is characterized by autoantibody binding to desmoglein 1 and/or 3 (dsg1/dsg3). In this study we show that EGF receptor (EGFR) is activated following pemphigus vulgaris (PV) IgG treatment of primary human keratinocytes and that EGFR activation is downstream of p38 mitogen-activated protein kinase (p38). Inhibition of EGFR blocked PV IgG-triggered dsg3 endocytosis, keratin intermediate filament retraction, and loss of cell-cell adhesion in vitro. Significantly, inhibiting EGFR prevented PV IgG-induced blister formation in the passive transfer mouse model of pemphigus. These data demonstrate cross-talk between dsg3 and EGFR, that this cross-talk is regulated by p38, and that EGFR is a potential therapeutic target for pemphigus. Small-molecule inhibitors and monoclonal antibodies directed against EGFR are currently used to treat several types of solid tumors. This study provides the experimental rationale for investigating the use of EGFR inhibitors in pemphigus.     

Desmoglein 2 Compensates for Desmoglein 3 but Does Not Control Cell Adhesion via Regulation of p38 Mitogen-activated Protein Kinase in Keratinocytes

Desmosomal cadherins are transmembrane adhesion molecules that provide cell adhesion by interacting in the intercellular space of adjacent cells. In keratinocytes, several desmoglein (Dsg1–4) and desmocollin (Dsc1–3) isoforms are coexpressed. We have shown previously that Dsg2 is less important for keratinocyte cohesion compared with Dsg3 and that the latter forms a complex with p38 MAPK. In this study, we compared the involvement of Dsg2 and Dsg3 in the p38 MAPK-dependent regulation of keratinocyte cohesion. We show that loss of cell adhesion and keratin filament retraction induced by Dsg3 depletion is ameliorated by specific p38 MAPK inhibition. Furthermore, in contrast to depletion of Dsg2, siRNA-mediated silencing of Dsg3 induced p38 MAPK activation, which is in line with immunoprecipitation experiments demonstrating the interaction of activated p38 MAPK with Dsg3 but not with Dsg2. Cell fractionation into a cytoskeleton-unbound and a cytoskeleton-anchored desmosome-containing pool revealed that Dsg3, in contrast to Dsg2, is present in relevant amounts in the unbound pool in which activated p38 MAPK is predominantly detectable. Moreover, because loss of cell adhesion by Dsg3 depletion was partially rescued by p38 MAPK inhibition, we conclude that, besides its function as an adhesion molecule, Dsg3 is strengthening cell cohesion via modulation of p38 MAPK-dependent keratin filament reorganization. Nevertheless, because subsequent targeting of Dsg3 in Dsg2-depleted cells led to drastically enhanced keratinocyte dissociation and Dsg2 was enhanced at the membrane in Dsg3 knockout cells, we conclude that Dsg2 compensates for Dsg3 loss of function.     

p38 MAPK activation is downstream of the loss of intercellular adhesion in pemphigus vulgaris

Pemphigus vulgaris (PV) is a potentially fatal blistering disease characterized by autoantibodies against the desmosomal adhesion protein desmoglein (Dsg) 3. Whether autoantibody steric hindrance or signaling through pathways such as p38 MAPK is primary in disease pathogenesis is controversial. PV mAbs that cause endocytosis of Dsg3 but do not dissociate keratinocytes because of compensatory adhesion by Dsg1 do not activate p38. The same mAbs plus exfoliative toxin to inactivate Dsg1 but not exfoliative toxin alone activate p38, suggesting that p38 activation is secondary to loss of adhesion. Mice with epidermal p38α deficiency blister after passive transfer of PV mAbs; however, acantholytic cells retain cell surface Dsg3 compared with wild-type mice. In cultured keratinocytes, p38 knockdown prevents loss of desmosomal Dsg3 by PV mAbs, and exogenous p38 activation causes internalization of Dsg3, desmocollin 3, and desmoplakin. p38α MAPK is therefore not required for the loss of intercellular adhesion in PV, but may function downstream to augment blistering via Dsg3 endocytosis. Treatments aimed at increasing keratinocyte adhesion could be used in conjunction with immunosuppressive agents, potentially leading to safer and more effective combination therapy regimens.     

p38 MAPK介导高糖诱导的肾小管上皮细胞向间充质细胞转变

本文旨在观察p38MAPK与高糖诱导的肾小管上皮细胞向间充质细胞转变之间的关系。将雄性Sprague—Dawley（SD）大鼠随机分为对照组、糖尿病组、胰岛素治疗组,用免疫组织化学、Western blot检测p38MAPK和磷酸化p38MAPK（P—p38MAPK）蛋白表达。采用机械分离和酶消化获取SD大鼠肾小管节段,进行肾小管上皮细胞培养,将肾小管上皮细胞分为对照组、高渗组（20mmol／L D—mannitol）、高糖组（20mmol／L D—glucose）和SB202190（p38MAPK特异性抑制剂）＋高糖组,处理72h后收集细胞,用免疫细胞化学检测α-平滑肌肌动蛋白（α—smooth muscleactin,α-SMA）、p-p38MAPK和Snaill蛋白表达,Western blot检测p38MAPK、p-p38MAPK、Snaill、转化生长因子β1（transforming growth factor—β1,TGF-β1）、α-SMA和E-cadherin的表达,RT-PCR检测α-SMA和E-cadherin mRNA的表达。体内和体外结果均显示,高糖状态激活了p38MAPK,这种活化作用在体内可因胰岛素控制血糖而被消除,在体外可被p38MAPK特异性抑制剂SB202190显著抑制;高糖组α-SMA蛋白和mRNA在原代培养肾小管上皮细胞的表达较对照组分别增加12倍和8倍（P〈0．01）,SB202190处理组其表达则较高糖组分别减少67％和50％（P〈0．01）。SB202190不影响TGF—β1蛋白表达,但下调Snaill蛋白表达,并部分恢复高糖组E—cadherin蛋白和mRNA的表达。上述结果提示,p38MAPK可能通过转录因子Snaill介导高糖诱导的肾小管上皮细胞向间充质细胞转变。     

p38 MAPK inhibition is critically involved in VEGFR-2-mediated endothelial cell survival

Vascular endothelial growth factor (VEGF) promotes vasculogenesis, arteriogenesis, and angiogenesis by stimulating proliferation, migration, and cell survival of endothelial cells. VEGF mediates its actions through activation of two receptor tyrosine kinases, VEGFR-1 and VEGFR-2. Serum starvation led to apoptosis of human umbilical vein endothelial cells (HUVEC), which was accompanied by activation of p38 MAPK and caspase-3. Stimulation of both VEGF-receptors resulted in a considerable decrease of apoptosis, which was associated with the inhibition of p38 MAPK and caspase-3 activity. Selective stimulation of VEGFR-2 showed similar results, whereas the isolated activation of VEGFR-1 was without effect. Incubation of HUVEC with SB203580, a p38 MAPK inhibitor, resulted in similar effects as VEGF-stimulation: p38 MAPK and caspase-3 enzyme activity were reduced and apoptosis was prevented. These data indicate that activation of VEGFR-2 prevents endothelial cell apoptosis by inhibiting p38 MAPK phosphorylation and thus, reducing caspase-3 activity.     

p38 MAPK signaling during murine preimplantation development

Mitogen-activated protein kinase (MAPK) pathways mediate some important cellular processes and are likely to also regulate preimplantation development. The role of p38 MAP kinase signaling during murine preimplantation development was investigated in the present study. p38 MAPK, p38-regulated or -activated kinase (PRAK; MK5), map kinase-activated protein kinase 2 (MK2), and heat shock protein 25 (hsp25) mRNAs and proteins were detected throughout preimplantation development. Two-cell stage embryos cultured in the presence of SB220025 and SB203580 (specific inhibitors of p38 MAPK alpha/beta), progressed to the eight-cell stage with the same frequency as controls; however, treated embryos halted their development at the 8- to 16-cell stage. In addition, embryos treated with p38 MAPK inhibitors displayed a complete loss of MK2 and hsp25 phosphorylation and also a complete loss of filamentous actin as indicated by the absence of rhodamine-phalloidin staining. In these inhibitor-treated groups, the embryos were composed of a mixture of compacting and noncompacting cells, and the embryos were one to two cell divisions behind controls. Treated embryos remained viable as the developmental blockade was rescued by removing embryos from the drug treatment and placing them in drug-free medium until they progressed to the blastocyst stage. This study demonstrates that p38 MAPK activity is required to support development through the murine preimplantation interval.     

p38 MAPK在小鼠睾丸不同发育阶段的表达和定位

为探讨丝裂原活化蛋白激酶p38 MAPK在小鼠睾丸不同发育阶段的表达,应用蛋白质免疫印迹杂交技术和免疫组织化学SABC法检测1至7周龄小鼠睾丸p38 MAPK的表达、定位及发育变化,并通过图像分析技术对免疫组织化学结果进行统计学分析。免疫印迹杂交发现,p38 MAPK在2～7周龄小鼠睾丸中均有表达。免疫组织化学结果显示,在2周龄小鼠睾丸曲细精管上皮中即可观察到p38 MAPK免疫阳性反应,免疫反应阳性细胞为精原细胞;3、4、5周龄小鼠睾丸仅有个别曲细精管上皮可见p38 MAPK免疫阳性反应;6、7周龄小鼠睾丸中p38 MAPK表达较丰富,免疫反应阳性细胞为精原细胞和初级精母细胞,免疫阳性反应物均主要位于细胞核内。在7周龄小鼠睾丸中还可见到部分间质细胞的细胞质亦呈p38 MAPK阳性。这些结果提示,p38 MAPK可能对生精细胞的增殖分化具有调控作用。     

The suppressive role of p38 MAPK in cellular vacuole formation

Vacuolization of the cytoplasm is one of the dramatic and frequently observed phenomena in various cell types. Cellular vacuoles occur spontaneously or via a wide range of inductive stimuli, but the molecular mechanism involved in this process remains largely unknown. In this study, we investigated the role of the p38 and JNK pathways in the formation of cytoplasmic vacuoles. We found that p38 and JNK agonist anisomycin abolishes spontaneous cytoplasmic vacuolization of HepG2 cells through p38 activation, but not through JNK activation. Importantly, blocking the activity of p38 or suppression the expression of p38 elicits cytoplasmic vacuoles formation in various cancer cells. Furthermore, cytoplasmic vacuoles induced by p38 blocking are derived from the perinuclear region. These observations provide direct evidence for a role of p38 signaling in regulating the formation of cytoplasmic vacuoles. J. Cell. Biochem. 114: 1789–1799, 2013. © 2013 Wiley Periodicals, Inc.     

巨噬细胞免疫调变信号:Raf-1,MAPK p44,MAPK p42和p38 MAPK的研究

为了了解巨噬细胞免疫调变机理,我们应用LPS和PMA处理小鼠抑制性巨噬细胞,观察到Ras下游信号分子Raf-1,分裂原激活蛋白激酶MAPK p44,MAPK p42和p38 MAPK均被活化,发现forskolin能增强p38 MAPK的活性,进一步提示PKC和PKA途径增强了p38 MAPK的磷酸化效应,为我们了解LPS如何激活p38 MAPK信号通路提供了一个新的机会。     

p38 MAPK信号转导途径在关节软骨细胞中的激活和作用

p38信号转导途径是MAPK途径的一种,软骨细胞是关节软骨中唯一的细胞成分。软骨细胞中的p38 MAPK可以被多种细胞因子、机械因素等所激活,它与软骨细胞表型的保持和分化、软骨细胞的肥大化和钙化、凋亡、软骨基质金属蛋白酶的合成、软骨炎性细胞因子的产生等有密切关系,可能在关节炎的发生发展中发挥了重要作用。     

p38 MAPK interacts with actin and modulates filament assembly during skeletal muscle differentiation

Skeletal muscle differentiation is marked by enhanced myotube formation and increased cytoskeletal rearrangement. Actin, a cytoskeletal protein is involved in various cellular functions such as glucose transport, intracellular trafficking, cell shape, and coordinated cell movement in response to various extracellular signals. The present study reveals an association between actin and p38 MAPK only in differentiated myotubes, not in proliferating myoblasts. Actin filament disassembly caused by cytochalasinD can be reversed using the potent activator of p38 MAPK, anisomycin. Pretreatment of myotubes with anisomycin partially resisted the effect of cytochalasinD. However, inhibition of p38 MAPK completely abolished the anisomycin-mediated actin remodeling. Data suggests that p38 MAPK interacts with actin and modulates actin filament rearrangement in differentiated L6E9 skeletal muscle cells.     

抑制p38MAPK信号通路对Bpiv3复制的影响

由牛副流感病毒3型(Bovine parainfluenza virus type 3,Bpiv3)感染引起的牛副流感病已成为各国牛场最重要的传染病之一,每年都会给世界养牛业造成巨大的经济损失,但关于该病致病的分子机制研究较少。本研究通过观察Bpiv3感染对MDBK细胞中丝裂原活化蛋白激酶(MKK3)及其下游分子p38丝裂酶原活化的蛋白激酶(p38MAPK)的表达的影响,探讨相关的信号转导机制,对p38 MAPK通路在Bpiv3感染过程中的作用进行了初步研究。Bpiv3感染细胞后,采用Western Blot检测MKK3,p38 MAPK在蛋白水平的表达变化,并采用ELISA法检测细胞上清中IL-6,IL-8,IL-13和TNF-α的水平变化,采用SPSS 12软件进行统计学分析。结果表明,Bpiv3在感染后能够诱导MKK3的激活以及p38的磷酸化,激活了p38 MAPK信号通路。而且p38 MAPK信号通路参与了Bpiv3的复制过程。ELISA检测Bpiv3感染后以及使用抑制剂SB202190处理后的细胞上清中IL-6、IL-8、IL-13和TNF-α的水平发现,p38 MAPK信号通路参与了Bpiv3诱导的炎症反应。研究证实Bpiv3感染能够激活p38 MAPK通路,显著上调MKK3的表达并诱导p38发生磷酸化,进一步激活下游分子发挥生物学活性,促进Bpiv3的复制及诱导促炎细胞因子的产生。p38 MAPK信号通路的激活可能是Bpiv3感染诱发炎症反应的机制之一。     

Genistein enhances TRAIL-induced apoptosis through inhibition of p38 MAPK signaling in human hepatocellular carcinoma Hep3B cells

The cytotoxic effect of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is limited in some carcinoma cancer cells. However, it was found that treatment with TRAIL in combination with nontoxic concentrations of genistein sensitized TRAIL-resistant human hepatocellular carcinoma Hep3B cells to TRAIL-mediated apoptosis. Combined treatment with genistein and TRAIL-induced chromatin condensation and sub-G1 phase DNA content. These indicators of apoptosis were correlated with the induction of caspase activity that resulted in the cleavage of poly(ADP-ribose) polymerase (PARP). Both cell viability and the cleavage of PARP induced by combined treatment were significantly inhibited by caspase-3, -8 and -9 inhibitors, which demonstrates the important roles of caspases in the observed cytotoxic effects. Genistein treatment also triggered the inhibition of p38-β mitogen-activated protein kinase (MAPK) activation. Pretreatment with SB203580 resulted in significantly increased sub-G1 population and loss of mitochondrial membrane potential (MMP) in TRAIL-induced apoptosis. By contrast, overexpression of p38 MAPK protected apoptosis by co-treatment with genistein and TRAIL, suggesting that the p38 MAPK act as key regulators of apoptosis in response to treatment with a combination of genistein and TRAIL in human hepatocellular carcinoma Hep3B cells.     

p38alpha MAPK can positively or negatively regulate Rac-1 activity depending on the presence of serum

The small GTP-ase Rac-1 can trigger p38 MAPK activation and, in turn, p38alpha can regulate signalling pathways that potentially impinge on Rac-1 activity. We have investigated the cross-talk between p38alpha and Rac-1 and found that p38alpha regulates the association between Rac-1 and caveolin-1 in serum-deprived cardiomyocytes. This interaction depends on cell attachment and correlates with higher levels of active Rac-1. Actin organization might regulate the formation of Rac-1-caveolin-1 complexes. In contrast, the Rac-1-caveolin-1 interaction is almost undetectable in the presence of serum, where Rac-1 activity is negatively regulated by p38alpha. Our results indicate that p38alpha can differentially contribute to Rac-1 activation depending on the presence of serum.     

p38 MAPK通路在脂多糖致呼吸道上皮损伤中的作用

脂多糖（Lipopolysaccharide,LPS）是革兰阴性杆菌细胞壁的主要组成成分,也是一种很强的炎症反应和氧化应激诱导剂。呼吸道上皮是机体防御外界细菌、病毒、香烟烟雾等生物和化学因素损伤的天然屏障,在维持呼吸道局部微环境稳态中可发挥重要作用,也是吸入性药物治疗的主要靶细胞。呼吸道上皮结构完整性缺陷或功能紊乱还参与了哮喘、慢性阻塞性肺疾病等多种肺部疾病的发生和发展。LPS可引起呼吸道上皮损伤,但其具体的分子机制目前尚不清楚。p38丝裂原活化蛋白激酶（P38mitogen-activated protein kinase,p38 MAPK）作为MAPK家族四个亚家族成员之一,包含四个成员：p38α、p38β、p38γ和p38δ,可通过经典和非经典的p38 MAPK信号通路激活方式及通过激酶活性无关的功能参与调控炎症反应、细胞生长、细胞分化和细胞死亡等多种病理生理过程。本文就p38 MAPK信号通路在LPS致呼吸道上皮损伤中的作用做一综述。