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.     

Interleukin-18 prevents apoptosis via PI3K/Akt pathway in normal human keratinocytes

Interleukin-18 (IL-18) is a pleiotropic cytokine expressed in both immune and non-immune cells. In the present study, we demonstrate an anti-apoptotic role of IL-18 in normal human neonatal foreskin epidermal keratinocytes (NHEK-F). Cultured NHEK-F spontaneously produced the active form of IL-18. Treatment of NHEK-F cells with anti-IL-18 receptor alpha-chain neutralizing antibody increased apoptosis and caspase-3 activity. Exogenous IL-18 augmented phosphorylation of Akt and activation of NF-kappaB. The promotion of Akt phosphorylation by IL-18 was abolished by LY294002, a PI3K inhibitor, but not SN50, an NF-kappaB inhibitor, indicating that IL-18 functions via the PI3K/Akt pathway and independently of NF-kappaB. In addition, IL-18 was found to augment expression of anti-apoptotic proteins, Bcl-2, XIAP and glucose regulated protein78/BiP, while anti-IL-18 receptor alpha-chain neutralizing antibody suppressed expression of Bcl-2, XIAP, glucose regulated protein94 and protein disulfide isomerase. Taken together, these results indicate that IL-18 plays an important role in keratinocyte survival.     

麦冬皂苷B通过抑制PI3K/Akt/mTOR通路诱导人黑色素瘤A375细胞凋亡

目的探讨麦冬皂苷B对人黑色素瘤(Melanoma)A375细胞增殖,凋亡和细胞周期的影响以及相关机制。方法麦冬皂苷B处理A375细胞后,采用CCK-8法检测细胞活力;流式细胞仪检测A375细胞周期变化及细胞凋亡水平;Hoechst33258荧光染色法观察细胞凋亡形态;免疫印迹法检测麦冬皂苷B对A375细胞PI3K,p-PI3K,AKT,p-AKT蛋白以及通路下游凋亡相关蛋白Bcl-2,Bax,Cleaved-caspase3表达的影响。结果麦冬皂苷B能抑制A375细胞增殖活力及PI3K/Akt/mTOR通路的活化;麦冬皂苷B促进了A375细胞内Bax和Cleaved-caspase 3的表达,抑制Bcl-2表达,诱导人黑色素瘤细胞发生凋亡;麦冬皂苷B阻滞了A375细胞细胞周期,G0/G1期细胞比例明显升高;PI3K/Akt/mTOR通路活化剂IGF-1处理A375细胞后抑制了麦冬皂苷B的上述作用。结论麦冬皂苷B能抑制A375细胞的增殖,诱导细胞发生凋亡,阻滞细胞周期于G0/G1期。     

Negative feedback regulation of phosphatidylinositol 3-kinase/Akt pathway by over-expressed cyclooxygenase-2 in human epidermal cancer cells

While enhanced expression of cyclooxygenase (COX)-2 has been observed in human skin epidermal cancer, the mechanisms underlying COX-2 expression have not been completely elucidated. Recently, a role for the phosphatidylinositol-3 (PI3) kinase pathway in COX-2 expression has attracted attention. We investigated COX-2 expression, PI3 kinase activity, and the phosphorylation level of Akt, a downstream effector of PI3 kinase, in the human skin cancer cell line HSC-5. Compared to the nontumorigenic keratinocyte HaCaT, in HSC-5 cells, COX-2 protein expression and PI3 kinase activity were increased. The PI3 kinase inhibitor LY294002 reduced COX-2 expression in HSC-5 cells and, contrary to our expectation, the phosphorylation of Akt was significantly decreased. The expression of Bcl-2, which is regulated by Akt, was reduced, and apoptosis was induced in HSC-5 cells compared to HaCaT cells. COX-2 inhibitor NS398 up-regulated Akt phosphorylation. These results imply that constitutively over-expressed COX-2 down-regulates the Akt phosphorylation through a negative feedback mechanism.     

五倍子瘢痕膏对瘢痕疙瘩miR-21/mTOR信号通路相关分子表达的影响

目的观察五倍子瘢痕膏对瘢痕疙瘩miR-21/mTOR信号通路关键分子miR-21、磷脂酰肌醇3-激酶(PI3K)、10号染色体张力缺失蛋白磷酸酶(PTEN)、蛋白激酶B(Akt)、哺乳动物雷帕霉素靶蛋白(mTOR)表达的影响。方法将36只裸鼠瘢痕疙瘩模型随机分成治疗组和对照组,每组18只。治疗组涂抹五倍子瘢痕膏,对照组仅涂抹制作五倍子瘢痕膏的基质,3次/d,连续30 d。然后分别应用逆转录聚合酶链反应(RT-PCR)和免疫组化技术检测治疗组、对照组及正常皮肤组中miR-21和PI3K、PTEN、Akt、mTOR的表达。结果RT-PCR检测结果显示,治疗组和正常皮肤组miR-21相对表达量差异无统计学意义(P>0.05,t=1.24),但二者与对照组相比均明显降低,差异有统计学意义(P<0.05,t=2.76、2.81);免疫组化检测结果显示,PI3K、Akt、mTOR在对照组中高表达,而在治疗组和正常皮肤组中低表达;PTEN在对照组中低表达,而在治疗组和正常皮肤组中高表达。结论五倍子瘢痕膏抑制瘢痕疙瘩成纤维细胞增殖的机制可能与其通过抑制miR-21表达而上调PTEN表达,进而下调mTOR信号通路中PI3K、Akt、mTOR表达有关。其中PTEN是负反馈调节因子;下游的核糖体蛋白S6激酶(S6K)、真核细胞翻译起始因子4E结合蛋白(4EBP),二者均是蛋白翻译的关键调节因子。     

葡萄籽原花青素对人皮肤鳞状细胞癌A431细胞增殖和凋亡的影响

目的：明确葡萄籽原花青素（GSP）对人皮肤鳞状细胞癌A431细胞增殖和凋亡的影响。方法：体外培养A431细胞,用不同浓度的GSP（5、10、20、40、80 μg/mL）处理,采用MTT实验和克隆形成实验检测细胞活力和增殖能力,Western blot检测细胞通路PI3K/Akt/GSK-3β信号转导通路蛋白的表达。结果：随着GSP浓度增加,A431细胞活力及细胞克隆逐渐下降,细胞凋亡逐渐增加。GSP处理后A431细胞中p-PI3K、p-Akt和p-GSK-3β表达水平明显降低。结论：GSP可以诱导A431细胞凋亡和抑制A431细胞增殖,其机制可能与抑制PI3K/Akt/GSK-3β信号通路活化有关。     

白藜芦醇对病理性瘢痕成纤维细胞mTOR信号通路相关分子表达的影响

目的观察白藜芦醇对病理性瘢痕成纤维细胞mTOR信号通路关键分子PI3K、Akt、mTOR表达的影响。方法应用免疫荧光检测PI3K、Akt、mTOR在病理性瘢痕及正常皮肤组织成纤维细胞中的表达;病理性瘢痕成纤维细胞经不同浓度白藜芦醇处理后,分别应用RT-PCR、Western Blot检测PI3K、Akt、mTOR mRNA和蛋白的表达。结果免疫荧光检测结果显示,PI3K、Akt、mTOR在病理性瘢痕成纤维细胞中表达明显增强,且主要表达于细胞核,而在正常皮肤组织成纤维细胞中未见明显表达;RT-PCR及Western Blot检测结果显示,病理性瘢痕成纤维细胞经不同浓度的Res干预后,Akt和mTOR mRNA和蛋白表达量降低,并且呈剂量依赖关系,与对照组相比,差异具有统计学意义(P0.05),而PI3K mRNA和蛋白表达量降低不明显,与对照组相比差异无统计学意义(P0.05)。结论白藜芦醇抑制病理性瘢痕成纤维细胞增殖的机制可能与其下调mTOR信号通路关键分子Akt、mTOR表达有关。     

Impaired PI3K/Akt activation-mediated NF-kappaB inactivation under elevated TNF-alpha is more vulnerable to apoptosis in vitiliginous keratinocytes

Levels of the cytokines IL-6, IL-1alpha, and tumor necrosis factor-alpha (TNF-alpha) are significantly higher in lesional than in non-lesional skin of patients with vitiligo. However, how cytokines affect pigmentation is not fully understood. To examine the mechanism, Western blot analysis with TNF-alpha, Fas ligand (FasL), and downstream signaling molecules such as I-kappaB, NF-kappaB, TNF-R1-associated factor 2, Akt, and PTEN (phosphatase and tension homologue) were performed for the suction-blistered depigmented and normally pigmented epidermis from 10 patients. Levels of TNF-alpha and FasL were significantly higher in the depigmented epidermis. Interestingly, phosphorylation levels of I-kappaB, NF-kappaB, and Akt were lower in the depigmented epidermis. Moreover, PTEN, which could inhibit the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway, was significantly higher in depigmented epidermis, implying that vitiliginous keratinocytes may be more susceptible to TNF-alpha-mediated apoptosis through impaired Akt and NF-kappaB activation. To test this hypothesis, cultured normal human keratinocytes were treated with TNF-alpha in the presence of a PI3K inhibitor to suppress Akt activation. Keratinocytes showing impaired Akt activation demonstrated increased apoptosis with less activation of NF-kappaB. Thus, reduced activation of NF-kappaB via impaired PI3K/Akt activation under increased TNF-alpha levels could result in increased apoptosis of vitiliginous keratinocytes.     

CD109 release from the cell surface in human keratinocytes regulates TGF-β receptor expression, TGF-β signalling and STAT3 activation: relevance to psoriasis

Transforming growth factor (TGF)-β is an important cytokine that negatively regulates keratinocyte proliferation. Deregulation of TGF-β signalling has been reported in psoriasis, where despite increased expression of TGF-β, psoriatic keratinocytes continue to hyperproliferate. Recently, we have identified CD109, a glycosyl phosphatidylinositol (GPI)-anchored protein, as a novel co-receptor and negative regulator of TGF-β signalling. In the current work, we demonstrate that release of CD109 from the cell surface or the addition of CD109 protein results in downregulation of TGF-β signalling and TGF-β receptor expression in human keratinocytes. Moreover, these effects are associated with an increase in phospho-STAT3 levels, enhanced total STAT3 and Bcl-2 expression and an increase in cell growth and survival, suggesting that released/soluble CD109 is able to induce molecular changes that are known to occur in psoriasis. Analysis of CD109 expression in psoriasis patients reveals that CD109 protein expression is markedly decreased in psoriatic epidermis as compared to adjacent uninvolved skin. In contrast, CD109 mRNA expression is unchanged in psoriatic plaques in comparison with normal skin. This raises a possibility that CD109 protein release is enhanced in psoriatic keratinocytes. Furthermore, psoriatic epidermis displays decreased expression of TGF-β receptors, consistent with the results obtained in vitro in keratinocytes with CD109 release or addition of CD109 recombinant protein. Together our findings suggest that aberrant CD109 release from the cell surface in human keratinocytes may induce molecular changes that are usually observed in psoriasis and may explain TGF-β receptor downregulation and decrease in TGF-β signalling in psoriasis.     

Activation of Akt by mechanical stretching in human epidermal keratinocytes

Mechanical stretching represents an important part of the signaling in skin. We have previously demonstrated that mechanical stretching induced proliferative phenotypes in human keratinocytes, as shown in increased 5-bromo-2'-deoxyuridine (BrdU) incorporation, ERK1/2 activation, and keratin K6 induction. Here we have further investigated the antiapoptotic signals in human keratinocytes provoked by mechanical stretching in vitro. Keratinocytes were plated on flexible silicone supports to transmit mechanical stretching to keratinocytes, involving continuous stretching by +20%. Stretching of these cells for 15-30 min caused the phosphorylation and activation of Akt. Inhibition of mitogen and extracellular signal-regulated kinase (MEK1/2) with U0126 and phosphoinositide 3-OH kinase (PI 3-K) with Wortmannin attenuated Akt activation. The epidermal growth factor (EGF) receptor kinase inhibitor, AG1478, and calcium channel inhibitor, gadolinium (Gd3+), also inhibited Akt activation. In summary, our results demonstrate the activation of the Akt signaling pathway by mechanical stretching, generating not only proliferative but also antiapoptotic signals in human keratinocytes.     

Expression of matrix metalloproteinase-13 is controlled by IL-13 via PI3K/Akt3 and PKC-δ in normal human dermal fibroblasts

IL-13, a T helper type 2 cytokine, is reported to be increased in the tissue of patients with atopic dermatitis (AD). In addition, chronic lichenified plaques in AD show thickened epidermis and dermis. We hypothesized that IL-13 is involved in tissue remodeling by altering the expression of matrix metalloproteinases (MMPs). In this study, we examined the MMP-related genes targeted by IL-13 in human dermal fibroblasts using a complementary DNA microarray. We focused on the MMP-13 gene, which was identified as one of the MMPs suppressed by IL-13. IL-13 downregulated both MMP-13 protein and mRNA expression. IL-13 suppressed MMP-13 expression more effectively in the presence of protein kinase C (PKC)-δ inhibitor, whereas IL-13 upregulated MMP-13 in the presence of inhibitors of phosphoinositide 3-kinase (PI3K)/Akt pathway or Akt3-specific small interfering RNA. Our results suggest that MMP-13 expression is negatively controlled by PI3K/Akt3 and positively regulated by PKC-δ in the presence of IL-13. Taken together, these findings indicate that IL-13 may induce the formation of thickened dermis in AD by decreasing collagen degradation. Blockade of IL-13 signaling cascades in AD patients may be a new therapeutic approach.     

All-trans retinoic acid antagonizes UV-induced VEGF production and angiogenesis via the inhibition of ERK activation in human skin keratinocytes

Incident UV radiation leads to the upregulation of vascular endothelial growth factor (VEGF), a potent angiogenic factor, in human skin. However, the molecular basis of UV-induced angiogenesis in skin remains to be elucidated. In this study, we investigated the roles of UV exposure on cutaneous angiogenesis, its associated signaling mechanisms, and the effect of all-trans retinoic acid (tRA) on UV-induced vascularization, and VEGF expression. Using a human epidermal cell line, HaCaT, we found that UV induces VEGF mRNA and protein expression via the MAPK/ERK kinase-ERK1/2 (extracellular signal-regulated kinase 1/2) pathway but not via the phosphatidylinositol 3-kinase (PI3K)/Akt pathway, and that tRA pretreatment significantly inhibits UV-induced VEGF overexpression and ERK1/2 activation. In human skin in vivo, we confirmed that skin vascularization significantly increased after a single exposure to UV, as was evidenced by a prominent increase in vessel size, vascular density, and in the cutaneous area occupied by vessels, and we found that these events are associated with VEGF upregulation. Topical pretreatment with tRA under occlusion inhibited not only UV-induced VEGF upregulation and angiogenesis with a significant reduction of vessel density but also UV-induced ERK1/2 activation in human skin. Collectively, our data demonstrate that tRA inhibits the UV-induced angiogenic switch via downmodulation of ERK1/2 activation and consecutive VEGF overexpression. These findings may help us understand the molecular mechanisms that regulate skin angiogenesis due to UV exposure, and provide evidence of the potential of tRA in terms of preventing angiogenesis-associated skin damage following exposure to UV irradiation.     

The antimycotic agent clotrimazole inhibits melanogenesis by accelerating ERK and PI3K‐/Akt‐mediated tyrosinase degradation

Azole antimycotic agents are known to have anti‐inflammatory and anti‐cancer effects, which are mediated through their effects on the p38‐cyclooxygenase‐2 (COX‐2)‐prostaglandin E2 (PGE2) pathway, as well as anti‐oxidant effects. Furthermore, pyridinyl imidazole compounds, such as SB203580 have recently been shown to inhibit melanogenesis. Accordingly, we hypothesized that azole antifungal agents might affect skin pigmentation. We herein investigated the effect of clotrimazole, the most commonly used azole antifungal agent, on melanogenesis. Intriguingly, clotrimazole reduced the melanin content in human melanocytes and mouse melanocytes, as well as in B16F10 mouse melanoma cells. Clotrimazole reduced levels of tyrosinase protein without altering mRNA expression. Simultaneous treatment with a proteasomal inhibitor restored both the suppression of melanin synthesis, and the downregulation of tyrosinase level, by clotrimazole. Clotrimazole also induced the phosphorylation of extracellular signal‐regulated kinase (ERK) and PI3K/Akt, while each inhibitor of these two signals abolished the decrease of melanin synthesis by clotrimazole. Thus, our data suggest that clotrimazole inhibits melanin synthesis by promoting the proteasomal degradation of tyrosinase, which is mediated through activation of the ERK and Akt signaling pathways. These results may indicate a new role for clotrimazole as a molecular‐mechanism‐based, safe depigmenting agent for topical management of hyper‐pigmentary sequelae related to fungal infection, or for other skin inflammatory disorders.     

Akt/mTOR活化抗UVB诱导HaCaT细胞凋亡的研究

目的 探讨Akt/mTOR信号通路活化抗中波紫外线（UVB）诱导的HaCaT细胞凋亡。方法 UVB照射角质形成细胞,Western印迹检测Akt/mTOR通路中相关信号分子的动态水平变化。免疫荧光 Hoechst 33342染色观察HaCaT细胞凋亡率。结果 UVB能活化Akt/mTOR信号通路,并在一定范围内（5 ～ 30 mJ/cm2）成剂量依赖性,在一定范围内（5 ～ 30 min）成时间依赖性。EGFR抑制剂PD 153035、PI3K抑制剂LY 294002和mTOR抑制剂雷帕霉素能显著抑制UVB对Akt/mTOR信号通路的活化作用。UVB照射前加入雷帕霉素、LY 294002预处理,HaCaT细胞凋亡率增加。结论 Akt/mTOR活化抗UVB诱导的HaCaT细胞凋亡。     

TNF-alpha stimulates Akt by a distinct aPKC-dependent pathway in premalignant keratinocytes

Tumor necrosis factor-alpha (TNF-alpha) is an important proinflammatory cytokine involved in the pathogenesis of inflammatory skin diseases and cutaneous squamous cell carcinoma. Some of these effects are mediated by the stimulatory effect of this cytokine on the Akt signalling pathway, which renders keratinocytes less susceptible to proapoptotic stimuli and enhances cell growth. We have recently shown that TNF-alpha-induced Akt activation may promote the early stages of skin cancer. In this work, we demonstrate that in the premalignant keratinocyte cell line HaCaT, TNF-alpha activates Akt, ERK1/2 and p38. The specific peptide blocking the activity of the atypical protein kinase C (aPKC) species zeta and iota/lambda abrogated the effects of TNF-alpha on Akt and ERK1/2 but increased the activation of p38. The TNF-alpha-dependent phosphorylation of Akt-ERK1/2 was slightly decreased by NF kappaB inhibition and in the presence of p38 blockers. Akt/ERK signalling but not p38 activation was abolished in the presence of the iron chelator desferroxamine that blocks formation of hydroxyl ( OH) radicals. Thus, the TNF-alpha signalling in keratinocytes seems to bifurcate into an aPKC-, NFkB- and OH-dependent pathway resulting in the activation of survival and mitogenic pathways mediated by Akt and ERK1/2, and a signalling pathway conveyed by p38 that contributes to Akt activation but is suppressed by aPKC. Our data may be utilized in the development of more selective anti-TNF-alpha therapeutic strategies.     

TNF-alpha impairs the S-G2/M cell cycle checkpoint and cyclobutane pyrimidine dimer repair in premalignant skin cells: role of the PI3K-Akt pathway

Tumor necrosis factor-alpha (TNF-alpha) is induced by UVB radiation and has been implicated in the early stages of skin carcinogenesis. Here, we show that in normal keratinocytes and the transformed keratinocyte cell lines, HaCaT and A431, TNF-alpha stimulates protein kinase B/Akt, which results in activation of the survival complex mTORC1 (mammalian target of rapamycin complex 1) and inhibition of the proapoptotic proteins Bad and FoxO3a. In UVB-irradiated HaCaT cells (10-20 mJ cm(-2)), TNF-alpha increased the proportion of cycling cells and enhanced the rate of apoptosis. A significantly higher proportion of UVB-treated HaCaT cells containing unrepaired cyclobutane pyrimidine dimers (CPDs) escaped the G2/M cell cycle checkpoint in the presence of TNF-alpha (9.5+/-3.3 vs 4.8+/-2.2%). After treatment with the PI3K inhibitor LY294002, only 1.2+/-0.7% of CPD-containing HaCaT cells were actively cycling. TNF-alpha enhanced apoptosis less potently and did not increase the level of CPD or stimulate cell cycle progression in normal keratinocytes. Our data suggest that TNF-alpha overrides the G2/M checkpoint in premalignant skin cells and allows for some cells containing unrepaired CPD to enter the cell cycle. The effect of TNF-alpha seems to be dependent on Akt activation and may constitute a relevant mechanism enhancing mutagenesis and tumor development.     

S‐allyl cysteine inhibits TNF‐α‐induced inflammation in HaCaT keratinocytes by inhibition of NF‐ κB‐dependent gene expression via sustained ERK activation

Tumor necrosis factor‐α (TNF‐α)‐induced keratinocyte inflammation plays a key role in the pathogenesis of multiple inflammatory skin diseases. Here we investigated the anti‐inflammatory effect of S‐allyl cysteine (SAC) on TNF‐α‐induced HaCaT keratinocyte cells and the mechanism behind its anti‐inflammatory potential. SAC was found to inhibit TNF‐α‐stimulated cytokine expression. Further, SAC was found to inhibit TNF‐α‐induced activation of p38, JNK and NF‐κB pathways. Interestingly, SAC was found to differentially regulate ERK MAP kinase in cells. TNF‐α‐induced transient ERK activation and SAC treatment resulted in sustained ERK activation both in the presence and absence of TNF‐α. Additionally, SAC failed to inhibit the TNF‐α‐induced expression of the pro‐inflammatory cytokines TNF‐α and IL‐1β when cells were treated with the MEK inhibitor PD98059, suggesting that the anti‐inflammatory effect of SAC is via sustained activation of the ERK pathway. Since ERK activation has been reported to negatively regulate NF‐κB‐driven gene expression and we find that SAC activates ERK and negatively regulates NF‐κB, we investigated whether there existed any crosstalk between the ERK and the NF‐κB pathways. NF‐κB‐dependent reporter assay, visualization of the nuclear translocation of NF‐κB‐p65 subunit and determination of the cellular levels of I‐κB, the inhibitor of NF‐κB, revealed that SAC inhibited TNF‐α‐induced NF‐κB activation, and PD98059 treatment reversed this effect. These results collectively suggest that SAC inhibits TNF‐α‐induced inflammation in HaCaT cells via a combined effect entailing the inhibition of the p38 and the JNK pathways and NF‐κB pathway via the sustained activation of ERK.