光线性角化病和鳞状细胞癌表皮生长因子受体与MAPK信号通路的研究

目的 探讨磷酸化ERK1/2、JNK和p38MAPK与其上游因子表皮生长因子受体（EGFR）及下游转录因子Elk-1在光线性角化病（AK）和皮肤鳞状细胞癌（SCC）中的表达。 方法 收集确诊为AK和高、中、低分化SCC患者各30例的病变组织,同时收集30例非癌患者正常皮肤组织作为正常对照组。采用免疫组化及Western印迹法分别检测p-EGFR、p-ERK1/2、p-JNK、p-p38MAPK及p-Elk-1蛋白在AK和不同分化程度SCC中的表达情况。 结果 p-EGFR在SCC组中的表达高于AK组及正常对照组（P < 0.05）,AK组与正常对照组表达差异无统计学意义;p-ERK1/2、p-JNK、p-p38MAPK及p-Elk-1在SCC的表达均高于AK组及正常对照组（P < 0.05）,且在AK中的表达又均高于正常对照组（P < 0.05）。除p-EGFR和p-Elk-1在高分化和中分化SCC中的表达差异无统计学意义,p-ERK1/2、p-JNK、p-p38MAPK随着SCC分化程度的降低,其表达逐渐增高（P < 0.05）。相关性分析显示,在SCC中p-EGFR的表达与p-ERK1/2、p-JNK、p-p38MAPK的表达强度呈正相关（r = 0.843、0.819、0.902,均P < 0.01）,且p-Elk-1的表达与p-ERK1/2、p-JNK、p-p38MAPK的表达强度亦呈正相关（r = 0.874、0.843、0.893,均P < 0.01）;在AK中p-EGFR的表达仅与p-p38MAPK的表达强度呈正相关（r =0.707,P = 0.022）。 结论 p-EGFR、p-ERK1/2、p-JNK、p-p38MAPK及p- Elk-1蛋白在皮肤SCC中的表达与其病理分级有关。磷酸化EGFR→ERK1/2、JNK、p38MAPK→Elk-1信号转导途径可能在AK和SCC的发生发展中起作用。     

雷公藤内酯醇对HaCaT细胞表皮生长因子受体磷酸化及其下游信号激酶MEK的影响

目的 探讨雷公藤内酯醇对表皮生长因子(EGF)信号刺激HaCaT细胞后EGF受体磷酸化以及下游MEK途径的影响.方法 在HaCaT细胞培养体系中,用外源性重组人EGF为刺激信号,用免疫印迹法检测总EGF受体及其磷酸化受体,以及总MEK及其磷酸化激酶的表达.结果 雷公藤内酯醇对rhEGF引起的细胞总EGF受体表达无明显影响,但抑制磷酸化EGF受体表达,抑制作用呈剂量依赖性,IC₅₀值为2.38×10^-10mol/L.对细胞总MEK1/2表达也不影响,但明显下调磷酸化MEK,抑制作用的IC₅₀值约为6.03×10^-11mol/L.结论 雷公藤内酯醇对EGF信号引起的EGF受体磷酸化及下游MEK激酶磷酸化均有抑制作用.     

Differential expression of phosphorylated extracellular signal-regulated kinase 1/2, phosphorylated p38 mitogen-activated protein kinase and nuclear factor-κB p105/p50 in chronic inflammatory skin diseases

The keratinocytes actively participate in the cutaneous immune responses. Dysregulation and abnormal expression of inflammatory mediators or their receptors in keratinocytes are relevant to the pathogenesis of chronic inflammatory skin diseases. The mechanism of long-lasting inflammatory processes is related with the activation of nuclear factor (NF)-κB and mitogen-activated protein kinase (MAPK), which play a crucial role in the immune responses. There are potential interaction points between these two pathways. The aim of this study is to investigate the differences in expression levels and distributions of phosphorylated extracellular signal-regulated kinase (ERK)1/2, phosphorylated p38 MAPK and NF-κB p105/p50 in chronic inflammatory skin diseases. An immunohistochemical staining technique was employed to measure the expression of these molecules in 25 cases of lichen planus, 22 cases of psoriasis, 26 cases of chronic eczema, seven cases of prurigo and seven cases of normal skin. We observed that the expression of phosphorylated ERK1/2, phosphorylated p38 MAPK and NF-κB p105/p50 was significantly more augmented in the lesional epidermis of all the inflammatory skin diseases than those in normal skin ( P  < 0.05), and the number of positive keratinocytes was significantly more in lichen planus than that in other inflammatory diseases ( P  < 0.001). Moreover, the positive keratinocytes of these three molecules were more widely distributed in the entire layer of the epidermis in lichen planus than those in other diseases. We concluded that ERK1/2, p38 MAPK and NF-κB p105/p50 might play important roles in the pathophysiology of chronic inflammatory skin diseases.     

Heat-induced MMP-1 expression is mediated by TRPV1 through PKCalpha signaling in HaCaT cells

Background: Matrix metalloproteinase‐1 (MMP‐1) is considered a key initiator of collagen degradation in inflammatory responses. A heat‐gated channel, transient receptor potential vanilloid type 1 (TRPV1), induces release of proinflammatory mediators. TRPV1 channels have been localized to the epidermis and we have recently suggested that they act as mediators of heat‐induced MMP‐1. The aim of this study was to investigate the signaling of TRPV1 in MMP‐1 regulation by heat shock in human epidermal keratinocytes. Methods: Heat shock‐induced MMP‐1 expression was decreased by treatment with TRPV1 inhibitor. The heat‐induced MMP‐1 expression was suppressed by Gö6976 [calcium‐dependent inhibitor] and staurosporine (ST, broad‐spectrum PKC inhibitor), while rottlerin (ROT, calcium‐independent PKCδ inhibitor) had no effect. Also, transfection of PKCα siRNA decreased MMP‐1 expression, whereas MMP‐1 expression was not significantly affected in cells transfected with negative control siRNA, PKCβ siRNA or PKCδ siRNA. Results: We demonstrated that heat shock failed to induce MMP‐1 expression in HaCaT cells cultured in calcium‐free media. The heat‐induced [Ca²⁺]_i increase was inhibited by Gö6976 and ST, but not by ROT. We also found that heat‐induced phosphorylation of ERK, JNK and p38 MAPK in HaCaT cells, but capsazepine and ruthenium red had no effect on this activation. In addition to the role of TRPV1 in heat‐induced MMP‐1 expression, we also found that heat increased TRPV1 proteins in human skin in vivo. Conclusions: Our results suggest that TRPV1 mediates heat shock‐induced MMP‐1 expression via calcium‐dependent PKCα signaling in HaCaT cells.     

两性霉素B对人THP-1细胞产生肿瘤坏死因子α、白细胞介素8及p38MAPK活化的影响

目的 探讨两性霉素B对人急性单核细胞白血病细胞系THP-1细胞系分泌肿瘤坏死因子α(TNF-α)和白细胞介素8(IL-8)以及p38丝裂原活化蛋白激酶(MAPK)活化的影响.方法 将THP-1细胞分为空白对照组、两性霉素B组(分别加入2、4、8mg/L两性霉素B处理);阳性对照组(用100 μg/L β葡聚糖或者100 mg/L脂多糖处理).实时荧光定量PCR分析不同刺激物和THP-1细胞作用一定时间后TNF-α、IL-8 mRNA表达水平.酶联免疫吸附试验检测8 mg/L两性霉素B刺激THP-1细胞24 h后上清液中TNF-α分泌量.Western印迹检测8 mg/L两性霉素B作用THP-1细胞后p38MAPK和磷酸化p38MAPK的水平.结果 2、4、8 mg/L两性霉素B刺激6h,TNF-α mRNA水平分别为7.55±1.17、19.47±2.91、57.22±0.65,与空白对照组比较,差异均有统计学意义(P＜ 0.01、0.001、0.001).IL-8mRNA水平分别为2.98±0.04、5.22±1.35、11.82±1.66,与空白对照组比较,差异均有统计学意义(P＜ 0.01、0.001、0.001).8 mg/L两性霉素B刺激THP-1细胞1、3、6h后TNF-αmRNA水平分别为8.61±0.30、10.75±0.08、56.98±2.43,与空白对照组比较,差异均有统计学意义(P＜ 0.05、0.01、0.001).IL-8 mRNA水平分别为2.63±0.28、5.35±0.98、11.73±1.18,与空白对照组比较,差异均有统计学意义(P＜ 0.05、0.01、0.001).8mg/L两性霉素B刺激THP-1细胞24 h上清液中TNF-α蛋白水平为(4039.06±223.87) ng/L,与空白对照组比较差异有统计学意义(P＜ 0.001).结论 两性霉素B体外可促进人THP-1细胞p38MAPK蛋白磷酸化及TNF-α和IL-8分泌,具有免疫调节作用.     

Epidermal growth factor-induced matrix metalloproteinase-1 expression is negatively regulated by p38 MAPK in human skin fibroblasts

Background

Many extracellular stimuli, including epidermal growth factor (EGF), are known to induce MMP-1 expression. Recently, several reports have shown that ERK activity plays an important role in EGF-induced MMP-1 expression. However, EGF is also known to activate many signaling pathways in addition to the ERK pathway, but the roles of these pathways during the induction of MMP-1 by EGF are unclear.

Objective

We investigated the role of JNK, p38 MAPK, and PI3K/Akt pathways in EGF-induced MMP-1 expression in human skin fibroblasts. Then, we further explored the inhibitory effect of p38 MAPK pathway on EGF-induced MMP-1 expression and studied the molecular mechanisms involved in the processes.

Methods

Human skin fibroblasts were pretreated with various chemical inhibitors or small interfering RNA (siRNA) at the indicated concentrations and then treated with EGF, TNF-alpha, or IL-1beta for the indicated times. Protein and mRNA levels of various target molecules were assessed by Western blotting and quantitative real-time PCR, respectively.

Results

We found that EGF-induced MMP-1 expression was positively regulated by JNK as well as ERK but negatively regulated by p38 MAPK in human skin fibroblasts. On the other hand, the PI3K/Akt pathway did not significantly affect MMP-1 induction by EGF. Then we found that the inhibition of p38 MAPK pathway specifically increased the MMP-1 expression stimulated by EGF but not by TNF-alpha or IL-1beta, indicating that the effect of p38 MAPK on MMP-1 expression may be stimulus-type specific in human skin fibroblasts. In addition, the inhibitory effect of p38 MAPK on EGF-induced MMP-1 expression was shown to be mainly mediated by p38-alpha MAPK. Our further studies showed that the inhibition of p38 MAPK but not PI3K specifically increased EGF-induced ERK and JNK activations, and that the augmentation of EGF-induced MMP-1 expression by p38 MAPK inhibition was significantly attenuated by inhibiting the activities of ERK and/or JNK.

Conclusions

Our results indicate that EGF-induced MMP-1 expression is differentially regulated by the JNK, p38 MAPK, and PI3K/Akt pathways, and suggest that p38 MAPK negatively regulates EGF-induced MMP-1 expression by suppressing the activations of ERK and JNK.