Inflammatory Responses In Keratinocytes Research Articles

Pivotal roles of TRPV1 channel and Nrf2 factor in green light modulation of keratinocyte inflammatory response

Pivotal roles of TRPV1 channel and Nrf2 factor in green light modulation of keratinocyte inflammatory response

CYSLTR1 antagonist inhibits Th17 cell differentiation by regulating the NF-κB signaling for the treatment of psoriasis.

Cysteinyl leukotriene receptor 1 (CYSLTR1) is observed to increase in psoriatic skin lesions. Montelukast, a CYSLTR1 antagonist, effectively treats inflammatory disorders, such as rheumatoid arthritis, multiple sclerosis, and atopic dermatitis. Thus, blocking CYSLTR1 may be a promising strategy for psoriasis immunotherapy. We prepared a montelukast sodium cream and solution and investigated their effects on psoriasis-like skin lesions induced by imiquimod (IMQ). After the treatment, serum, skin, and spleen samples were collected for evaluation. We treated human T helper (Th) 17 cells with montelukast in vitro to study its effect on Th17 differentiation and nuclear factor kappa-B (NF-κB) signaling. We also created a keratinocyte proliferation model induced by M5 cytokines and assessed the influence of montelukast on key psoriasis-related genes. We induced psoriasis in CYSLTR1 knockout (KO) mice using IMQ to explore the role of CYSLTR1 in psoriasis development. Montelukast sodium cream and solution effectively reduced the psoriasis area and severity index (PASI) and alleviated disease symptoms in IMQ-induced mice. Furthermore, reduced infiltration of inflammatory cells (Th1, Th17, and T follicular helper [Tfh] cells), decreased mRNA expression of cytokines in the skin (interleukin [IL]-17/F and IL-23), and lower serum concentrations of various cytokines (IL-2, IL-6, IL-13, and IL-17A/F) were observed. Montelukast cream and solution also decreased spleen size and the proportion of Th17 and Tfh cells, and significantly inhibited NF-κB signaling-related genes after application. Moreover, montelukast inhibited Th17 cell differentiation and suppressed NF-κB signaling in vitro. CYSLTR1 KO mice induced with IMQ showed improvement in PASI scores, serum IL-17A/F levels, and lower Th1 and Th17 cells in the spleen and skin compared to wild-type mice. Montelukast also suppressed the proliferation and inflammatory response of keratinocytes by regulating NF-κB signaling. Collectively, our results strongly indicate that inhibition of CYSLTR1 signaling to target the Th17 response holds significant promise as a therapeutic approach to manage psoriasis.

Treatment with a red-laser-based wound therapy device exerts positive effects in models of delayed keratinocyte and fibroblast wound healing.

Light therapy is widely used in medicine. Specifically, photobiomodulation has been shown to exert beneficial effects in wound healing disorders, which present a major challenge in health care. The study's aim was providing information on the effect of a novel, red-laser-based wound therapy device (WTD) on keratinocytes and fibroblasts during wound healing under optimal and non-optimal conditions. The scratch wound assay was employed as a wound healing model for mechanical damage with readjustment of specific cell milieus, explicitly chronic TH1 inflammation and TH2-dominant conditions. Furthermore, gene expression analysis of pro-inflammatory cytokines (IL1A, IL6, CXCL8), growth factors (TGFB1, PDGFC), transcription factors (NFKB1, TP53) and heat shock proteins (HSP90AA1, HSPA1A, HSPD1) as well as desmogleins (DSG1, DSG3) in keratinocytes and collagen (COL1A1, COL3A1) in fibroblasts was performed after WTD treatment. It was shown that WTD treatment is biocompatible and supports scratch wound closure under non-optimal conditions. A distinct enhancement of desmoglein and collagen gene expression as well as induction of early growth factor gene expression was observed under chronic inflammatory conditions. Moreover, WTD increased HSPD1 transcript levels in keratinocytes and augmented collagen expression in fibroblasts during wound healing under TH2 conditions. WTD treatment also alleviated the inflammatory response in keratinocytes and induced early growth factor gene expression in fibroblasts under physiological conditions. Positive effects described for wound treatment with WTD could be replicated invitro and seem to be to be conferred by a direct influence on cellular processes taking place in keratinocytes and fibroblasts during wound healing.

Ethylhexadecyldimethylammonium bromide, a quaternary ammonium compound, controls inflammatory response through NRF2 pathway in a human immortalized keratinocyte cell line.

Many everyday products contain quaternary ammonium compounds (QAC) and some of them are known to be skin irritants such as benzalkonium chloride. Others, such as didecyldimethylammonium chloride, have been shown to cause allergic contact dermatitis. Ethylhexadecyldimethylammonium bromide (EHD) is a QAC for which sensitization potential is not clearly known. Therefore, we have studied its mechanism in human keratinocytes (KC), the main cells of the epidermis. We used the well-described human KC cell line KERTr exposed to EHD, cinnamaldehyde (CinA), a well-known skin sensitizer, and a mixture of both. Since chemical sensitizers are known to activate the transcription factor nuclear factor (erythroid-derived 2)-like 2 (NRF2), leading to cellular detoxification and suppressed proinflammatory cytokines, protein or mRNA expression of NRF2 pathway-related enzymes and pro-inflammatory cytokines were investigated by Western blot and RT-qPCR. The activity of the NRF2 pathway on inflammation was studied by RT-qPCR in NRF2-invalidated KERTr cells. We showed that EHD cannot induce the NRF2 pathway, unlike contact sensitizers like CinA. EHD triggers an inflammatory response by inducing the mRNA expression of pro-inflammatory cytokines such as IL-1β or IL-6. Moreover, mixing EHD and CinA inhibits the effect of CinA on NRF2 expression and mitigates the inflammatory response induced by EHD alone. EHD treatment of KERTr cells in which NRF2 has been invalidated showed an exacerbation of the inflammatory response at the transcriptional level. Hence, EHD may elicit an inflammatory response in KC via the NF-κB pathway, which could lead to irritation when applied to the skin. This inflammation is negatively controlled by the basal activity of the NRF2 pathway.

Photobiomodulation Controls Keratinocytes Inflammatory Response through Nrf2 and Reduces Langerhans Cells Activation.

Photobiomodulation (PBM) is rapidly gaining traction as a valuable tool in dermatology for treating many inflammatory skin conditions using low levels of visible light or near-infrared radiation. However, the physiological regulatory pathways responsible for the anti-inflammatory effect of PBM have not been well defined. Since previous studies showed that nuclear factor-erythroid 2 like 2 (Nrf2) is a master regulator of the skin inflammatory response, we have addressed its role in controlling inflammation by PBM. Primary human keratinocytes (KCs) stimulated with 2,4-dinitrochlorobenzene (DNCB) to mimic pro-inflammatory stress were illuminated with two wavelengths: 660 nm or 520 nm. Both lights significantly reduced the mRNA expression of the DNCB-triggered TNF-α, IL-6, and IL-8 cytokines in KCs, while they enhanced Nrf2 pathway activation. PBM-induced Nrf2 is a key regulator of the inflammatory response in KCs since its absence abolished the regulatory effect of light on cytokines production. Further investigations of the mechanisms contributing to the immunoregulatory effect of PBM in inflamed human skin explants showed that 660 nm light prevented Langerhans cells migration into the dermis, preserving their dendricity, and decreased pro-inflammatory cytokine production compared to the DNCB-treated group. This study is the first to report that the PBM-mediated anti-inflammatory response in KCs is Nrf2-dependent and further support the role of PBM in skin immunomodulation. Therefore, PBM should be considered a promising alternative or complementary therapeutic approach for treating skin-related inflammatory diseases.

Viaminate ameliorates Propionibacterium acnes-induced acne via inhibition of the TLR2/NF-κB and MAPK pathways in rats.

Viaminate, a retinoic acid derivative developed in China, has been clinically used for acne treatment to regulate and control keratinocyte cell differentiation and proliferation, inhibit keratinization, reduce sebum secretion, and regulate immune and anti-inflammatory functions; however, its potential molecular mechanism has not yet been elucidated. Therefore, we induced ear acne in rats using Propionibacterium acnes and sebum application. Symptoms of ear redness, epidermal thickening, inflammatory reaction, keratin overproduction, subcutaneous oil, and triglyceride (TG) accumulation improved significantly in acne model rats treated with viaminate for 30days. Transcriptome analysis of rat skin tissues suggested that viaminate had significant regulatory effects on fatty acid metabolism and cellular keratinization pathways. Molecular target prediction suggested that toll-like receptor 2 (TLR2) may be a key target of viaminate's therapeutic mechanism. Western blotting results confirmed that viaminate inhibited the TLR2 and its downstream pathways, nuclear factor-kappa B (NF-κB) [NF-κB inhibitor alpha (IκBα)/NF-κB-p65] and mitogen-activated protein kinases (MAPKs) [MAPK p38/c-Jun N-terminal kinase (JNK)/extracellular regulated kinase 1/2 (ERK1/2)] in acne vulgaris rats. In vitro studies revealed that viaminate treatment attenuated P. acnes proliferation and P. acnes-induced inflammatory response in human keratinocytes and has an inhibitory effect on the activation of NF-κB and MAPKs, while overexpression of TLR2 attenuated these effects. In conclusion, viaminate ameliorates P. acnes-induced acne by inhibiting the proliferation and inflammatory response of keratinocytes, ascribed to the deactivation of the TLR2-mediated NF-κB and MAPK pathways.

Low curcumin concentrations combined with blue light inhibits cutibacterium acnes biofilm-induced inflammatory response through suppressing MAPK and NF-κB in keratinocytes

BackgroundCurcumin has been employed as a photosensitizer agent during photodynamic therapy (PDT). Cutibacterium acnes (C. acnes) can cause an inflammatory response in human keratinocytes; however, no research has been conducted to determine whether curcumin and its photodynamic properties can prevent this inflammatory reaction. ObjectiveWe hypothesized that curcumin may control the C. acnes biofilm-induced inflammatory response in keratinocytes, either alone or in combination with blue light photodynamic therapy. MethodsFollowing C. acnes biofilm stimulation, human primary keratinocytes were treated with 20 μM curcumin solution alone or 5 μM curcumin with combined blue light irradiation. The amount of secreted protein was measured using an ELISA kit. The expression levels of Toll-like receptor 2 (TLR2) and its downstream proteins were determined using western blot. ResultsTreatment with 20 μM curcumin, but not 5 μM curcumin, reduced the inflammatory response to C. acnes biofilms in keratinocytes by blocking the TLR2/MAPK/NF-κB pathway. Interestingly, 5 μM curcumin combined with blue light also reduced the C. acnes biofilm-induced inflammation indicated above by blocking the TLR2/MAPK/NF-κB pathway. ConclusionCurcumin alone, in sufficient concentrations, or low-concentration curcumin with blue light had anti-inflammatory activity on keratinocytes stimulated by C. acnes biofilms through inhibition of MAPK and NF-κB signaling pathways by downregulating TLR2 expression.

Heat-clearing and blood-cooling decoction alleviates psoriasis by suppressing proliferation and inflammatory response of keratinocytes via EZH2/NF-κB

Psoriasis is a chronic recurrent dermatological disease that patients always suffer from different comorbidities. Chinese herbal medicine has been commonly used in the treatment of psoriasis for a long history. However, the mechanism operating between Qing-Ying Dizhuo Decoction (QYDD) (a heat-clearing and blood-cooling decoction) and psoriasis remains unclear. This paper aimed to study the role of QYDD in psoriasis and its underlying mechanism. HaCaT cells were induced by a mixture of IL-22, IL-17A, oncostatin M, TNF-α and IL-1α (M5) to construct the in vitro model of psoriasis. CCK-8 assay was utilized to assess the cell proliferation ability. The expressions of KRT1, KRT6, TNF-α, IL-1β, IL-6, IL-23, EZH2, IκBα, p65 and IKK were determined by qRT-PCR, western blot and ELISA. M5 induction increased levels of KRT6, IL-1β, IL-6, TNF-α and IL-23, enhanced the proliferation ability of HaCaT cells and decreased KRT1 expression, while QYDD treatment reversed these trends. Overexpression of EZH2 reversed the inhibitory effects of QYDD on cell inflammatory response and proliferation of M5-induced HaCaT cells. QYDD suppressed M5-activated NF-κB signaling pathway as evidenced by decreased levels of phosphorylated IKK and p65 and increased level of phosphorylated IκBα, while overexpression of EZH2 offset, in part, the regulation of the NF-κB pathway by QYDD. An NF-κB activator (betulinic acid) weakened the inhibitory effect of QYDD on the inflammatory response of HaCaT keratinocytes. QYDD appears to inactivate the NF-κB signaling pathway by inhibiting EZH2, thereby repressing the proliferation and suppressing inflammatory response of HaCaT cells and attenuating psoriasis.

Dual RNA-Sequencing and Liquid Chromatography–Mass Spectrometry Unveil Specific Insights on the Pathogenicity of Trichophyton mentagrophytes Complex

Trichophyton mentagrophytes is increasingly considered to be a public health hazard because it causes the most severe manifestations of dermatophytosis. In this study, we performed a series of studies to determine the pathogenicity of the T.mentagrophytes complex. We show that the T.mentagrophytes complex interacts with keratinocytes through pattern-recognition receptors‒MAPK/noncanonical NF-κB pathways and that the hyphal form of T.mentagrophytes is responsible for the increased inflammatory responses in keratinocytes. Moreover, SN-38 is likely a toxin of T.mentagrophytes that induces apoptosis in keratinocytes both invivo and invitro. Our results explain the severe pathogenicity and destructiveness of T.mentagrophytes observed in the clinic and pave the way for designing novel toxin-directed therapies to improve patient outcomes.

P05-03 Photobiomodulation-induced Nrf2 partially controls the inflammatory response in keratinocytes

P05-03 Photobiomodulation-induced Nrf2 partially controls the inflammatory response in keratinocytes

011 A new immunocompetent skin model recapitulates molecular features of psoriasis

Psoriasis is a chronic inflammatory skin disease involving interactions between keratinocytes and both the innate and adaptive immune systems. The IL-17/IL-23 axis is described to drive the release of inflammatory and immune factors in keratinocytes (cytokines, antimicrobial peptides, chimiokines), which sit at the heart of an inflammation amplification loop. To this date, there are very few immunocompetent models recapitulating as close as possible psoriatic skin. In this context, the aim of this work was to develop a 3D model of psoriatic lesional skin summarizing biological features of the pathology. As the dialogue between Th17 lymphocytes (LTh17) and keratinocytes plays a central role in psoriasis pathogenesis, a model taking into account these two biological actors was developed. A reconstructed epidermis (RE) was co-cultured with differentiated LTh17. RE morphology as well as proliferation/differentiation imbalance and inflammatory immune response were explored. As it is reported in psoriatic lesions, results showed that IL-17 family cytokines were increased. Histological analysis demonstrated that the psoriatic mimic epidermis exhibited morphological changes. Moreover, mechanisms of proliferation and differentiation appeared profoundly altered while a high keratinocyte inflammatory response characteristic of psoriasis was observed. In conclusion, we have succeeded in designing a 3D in vitro model reproducing molecular alterations of psoriatic skin. The co-culture of the RE with differentiated LTh17 led to a typical inflammatory response in keratinocytes, thus proving the successful communication of the two biological compartments. This physiological relevant model is suitable for the assessment of natural therapeutic molecules dedicated to psoriasis treatment.

090 Inhibition of HMGB1 attenuates the inflammatory response in keratinocytes

Recessive dystrophic epidermolysis bullosa (RDEB) is a blistering skin disease caused by mutations in COL7A1, the gene encoding type VII collagen (C7). RDEB is characterized by chronic wounds and a high incidence of aggressive squamous cell carcinoma (SCC), the leading cause of death in this patient population. High mobility group box 1 (HMGB1) is a serum biomarker of disease severity in RDEB patients that may have a mechanistic role in promoting SCC carcinogenesis. HMGB1 is a chromatin-associated protein that has a dual role as a mediator of DNA repair in the nucleus and a damage-associated molecular pattern that stimulates the innate immune response when secreted extracellularly in response to inflammatory stimuli or cellular damage.

424 C10orf99 governs keratinocyte inflammatory response and barrier formation of the skin

The defense system of the skin has three layers: barrier, innate immunity, and acquired immunity. Epidermal keratinocytes participate in all these three processes and play central roles in the inflammatory responses. However, a shared molecule in keratinocytes that responds to diverse dangers and governs the protective machinery of the skin remains obscure. Here we report that the orphan gene C10orf99 plays a primary role in the innate response of keratinocytes and barrier formation in the skin.

Inflammatory Response Against Staphylococcus aureus via Intracellular Sensing of Nucleic Acids in Keratinocytes.

Staphylococcus aureus is one of the clinically most relevant pathogens causing infections. Humans are often exposed to S. aureus. In approximately one-third of the healthy population it can be found on the skin either for long or short periods as colonizing “commensals”, without inducing infections or an inflammatory immune response. While tolerating S. aureus seems to be limited to certain individuals and time periods in most cases, Staphylococcus epidermidis is tolerated permanently on the skin of almost all individuals without activating overwhelming skin inflammation. To investigate this, we co-cultured a keratinocyte cell line (HaCaT) with viable S. aureus or S. epidermidis to study the differences in the immune activation. S. aureus activated keratinocytes depicted by a profound IL-6 and IL-8 response, whereas S. epidermidis did not. Our data indicate that internalization of S. aureus and the subsequent intracellular sensing of bacterial nucleic acid may be essential for initiating inflammatory response in keratinocytes. Internalized dsRNA activates IL-6 and IL-8 release, but not TNF-α or IFNs by human keratinocytes. This is a non-specific effect of dsRNA, which can be induced using Poly(I:C), as well as RNA from S. aureus and S. epidermidis. However, only viable S. aureus were able to induce this response as these bacteria and not S. epidermidis were actively internalized by HaCaT. The stimulatory effect of S. aureus seems to be independent of the TLR3, -7 and -8 pathways.

PFN1 Prevents Psoriasis Pathogenesis through IκBζ Regulation

PFN1 is an actin-binding protein that regulates actin polymerization, cell proliferation, apoptosis, angiogenesis, and carcinogenesis. Its dysregulation has been reported in diverse pathologic diseases; however, the role of PFN1 in psoriasis has not yet been elucidated. In this study, we show that PFN1 expression is increased in both skin and serum of patients with psoriasis. PFN1 was markedly expressed in the epidermis of psoriatic lesions, and its expression positively correlated with psoriasis severity. IL-17A treatment of keratinocytes increased PFN1 expression, whereas TNF-α induced PFN1 expression and secretion. In addition, knockdown of PFN1 with short hairpin RNA resulted in an altered expression of psoriasis-associated inflammatory markers, HBD2, S100A7, S100A9, and Ki-67, and recombinant PFN1 suppressed the IL-17A‒induced inflammatory response in keratinocytes. Interestingly, recombinant PFN1 also suppressed IL-17A‒induced IκBζ, an important player in immune response in psoriasis. Collectively, our results show that PFN1 acts as a negative regulator of psoriatic inflammation through the suppression of IκBζ and that the balanced level of PFN1 is important for IκBζ regulation. Thus, the expression of PFN1 can be used as a biomarker for psoriasis severity, and it can be considered as a possible target for the treatment of psoriasis.

Artemisia anomala Herba Alleviates 2,4-Dinitrochlorobenzene-Induced Atopic Dermatitis-Like Skin Lesions in Mice and the Production of Pro-Inflammatory Mediators in Tumor Necrosis Factor Alpha-/Interferon Gamma-Induced HaCaT Cells.

Artemisia anomala S. Moore is a perennial herbaceous plant classified as Asteraceae of the genus Artemisia. Many species of Artemisia have been used as medicinal materials. Artemisia anomala S. Moore has been widely used in China to treat inflammatory diseases. However, the mechanism of its action on the keratinocyte inflammatory response is poorly understood. Here, we investigated the anti-inflammatory reaction of Artemisia anomala S. Moore ethanol extract (EAA) using human keratinocyte (HaCaT) cells, which involved investigating the nuclear factor kappa B (NF-κB), signal transducer, and activator of transcription-1 (STAT-1), as well as mitogen-activated protein kinase (MAPK) signaling pathways and atopic dermatitis-like skin lesions in mice. We elucidated the anti-inflammatory effects of EAA on tumor necrosis factor-α/interferon-γ (TNF-α/IFN-γ)-treated human keratinocyte cells and 2,4-dinitrochlorobenzene (DNCB)-induced atopic dermatitis (AD)-like mice. The levels of chemokines and cytokines (IL-8, IL-6, TARC, and RANTES) were determined by an enzyme-linked immunosorbent assay. The NF-κB, STAT-1, and MAPK signaling pathways in HaCaT cells were analyzed by western blotting. Thickening of the mice dorsal and ear skin was measured and inflammatory cell infiltration was observed by hematoxylin and eosin staining. Results showed that EAA suppressed IL-8, IL-6, TARC, and RANTES production. EAA inhibited nuclear translocation of NFκB and STAT-1, as well as reduced the levels of phosphorylated ERK MAPKs. EAA improved AD-like skin lesions in DNCB-treated mice. These findings suggest that EAA possesses stronger anti-inflammatory properties and can be useful as a functional food or candidate agent for AD.

Cinnamaldehyde inhibits psoriasis‑like inflammation bysuppressing proliferation and inflammatory response of keratinocytes via inhibition of NF‑κB and JNK signaling pathways.

Psoriasis is a systemic immune-mediated inflammatory disease characterized by uncontrolled keratinocyte proliferation and poor differentiation. Cinnamaldehyde (CIN) has been shown to inhibit the proliferation and inflammatory response of primary and immortalized immune cells. However, to the best of our knowledge, the role of CIN in the progression of psoriasis remains unclear. Therefore, the present study aimed to investigate the biological role of CIN in psoriasis. To mimic abnormal proliferation and differentiation in keratinocytes in vitro, normal human epidermal keratinocytes (NHEKs) were stimulated with M5 (IL-1α, IL-17A, IL-22, oncostatin M and TNF-α). The viability and proliferation of NHEKs were analyzed using Cell Counting Kit-8 and 5-Ethynyl-2′-deoxyuridine assays, respectively. Western blotting was used to analyze the expression levels of keratin 1, filaggrin and loricrin in NHEKs. The results of the present study revealed that CIN significantly inhibited the proliferation and cell cycle progression, and promoted the differentiation of M5-stimulated NHEKs. CIN also markedly attenuated the extent of oxidative stress-induced damage in M5-stimulated NHEKs. Moreover, CIN ameliorated M5-induced inflammatory injury in NHEKs, as evidenced by the decreased levels of multiple inflammatory factors. Furthermore, CIN notably downregulated the expression levels of phosphorylated (p)-inhibitor of NF-κB, p-p65 and p-JNK in M5-stimulated NHEKs. In conclusion, the present data suggested that CIN may protect NHEKs against M5-induced hyperproliferation and inflammatory injury via inhibition of NF-κB and JNK signaling pathways. These results provide a novel insight on the role of CIN in psoriasis.

MiR-221-3p as a Potential Biomarker for Patients with Psoriasis and Its Role in Inflammatory Responses in Keratinocytes

Introduction: This study investigated serum miR-221-3p levels in psoriatic patients and the characterization of serum miR-221-3p in keratinocyte inflammatory responses was further assessed. Methods: qRT-PCR was used to detect the expression level of miR-221-3p in the serum of 46 patients with psoriasis and 42 healthy controls. The receiver operating characteristic curve evaluated the diagnostic ability of miR-221-3p in psoriasis. The effect of miR-221-3p on HaCaT cell proliferation was detected by using a cell counting Kit-8 and Transwell. ELISA was used to detect serum and keratinocyte pro-inflammatory factors. Results: miR-221-3p was significantly increased in the serum of patients with psoriasis. The area under the curve was 0.861, the sensitivity was 80.4%, and the specificity was 85.7%. Serum miR-221-3p was positively correlated with the expression levels of tumor necrosis factor-α, interleukin (IL)-17A, and IL-22. Cell experiments showed that reducing the expression of miR-221-3p could significantly inhibit cell proliferation. Additionally, miR-221-3p downregulation also inhibited the release of some inflammatory factors in the HaCaT cells. Discussion/Conclusion: MiR-221-3p is a latent biomarker of psoriasis patients. Lower expression of miR-221-3p inhibits the cell proliferation and inflammatory responses of HaCaT cells, which offers a possible target for the therapeutic interventions of psoriasis.

Interleukin 17 Promotes Expression of Alarmins S100A8 and S100A9 During the Inflammatory Response of Keratinocytes.

Psoriasis is one of the most common immune-mediated inflammatory skin diseases. Expression and secretion of two pro-inflammatory molecules of the S100-alarmin family, S100A8 and S100A9, in keratinocytes is a hallmark of psoriasis, which is also characterized by an altered differentiation of keratinocytes. Dimers of S100A8/S100A9 (calprotectin) bind to Toll-like receptor 4 and induce an inflammatory response in target cells. Targeted deletion of S100A9 reduced the inflammatory phenotype of psoriasis-like inflammation in mice. A role of S100-alarmins in differentiation and activation of keratinocytes was suggested but has been never shown in primary keratinocytes. We now confirm that induction of S100-alarmins in an imiquimod-induced murine model of psoriasis-like skin inflammation was associated with an increased expression of interleukin (IL)-1α, IL-6, IL-17A, or TNFα. This association was confirmed in transcriptome data obtained from controls, lesional and non-lesional skin of psoriasis patients, and a down-regulation of S100-alarmin expression after IL-17 directed therapy. However, analyzing primary S100A9−/− keratinocytes we found that expression of S100A8/S100A9 has no significant role for the maturation and inflammatory response pattern of keratinocytes. Moreover, keratinocytes are no target cells for the pro-inflammatory effects of S100A8/S100A9. However, different cytokines, especially IL-17A and F, highly abundant in psoriasis, strongly induced expression of S100-alarmins preferentially during early maturation stages of keratinocytes. Our data indicate that expression of S100A8 and S100A9 does not primarily influence maturation or activation of keratinocytes but rather represents the inflammatory response of these cells during psoriasis.

PARP-1 involves in UVB-induced inflammatory response in keratinocytes and skin injury via regulation of ROS-dependent EGFR transactivation and p38 signaling.

UV irradiation can injure the epidermis, resulting in sunburn, inflammation, and cutaneous tissue disorders. Previous studies demonstrate that EGFR in keratinocytes can be activated by UVB and contributes to inflammation. Poly (ADP-ribose) polymerase-1 (PARP-1) is a nuclear enzyme and plays an essential role in DNA repair under moderate stress. In this study, we set out to understand how PARP-1 regulates UVB irradiation-induced skin injury and interplays with EGFR to mediate the inflammation response. We found that PARP-1 deficiency exacerbated the UVB-induced inflammation, water loss, and back skin damage in mice. In human primary keratinocytes, UVB can activate PARP-1 and enhance DNA damage upon PARP-1 gene silencing. Moreover, PARP-1 silencing and PARP inhibitor olaparib can suppress UVB-induced COX-2 and MMP-1 expression, but enhance TNF-α and IL-8 expression. In addition, EGFR silencing or EGFR inhibition by gefitinib can decrease UVB-induced COX-2, TNF-α, and IL-8 expression, suggesting EGFR activation via paracrine action can mediate UVB-induced inflammation responses. Immunoblotting data revealed that PARP-1 inhibition decreases UVB-induced EGFR and p38 activation. Pharmacological inhibition of p38 also dramatically led to the attenuation of UVB-induced inflammatory gene expression. Of note, genetic ablation of PARP-1 or EGFR can attenuate UVB-induced ROS production, and antioxidant NAC can attenuate UVB-induced EGFR-p38 signaling axis and PARP-1 activation. These data suggest the regulatory loops among EGFR, PARP-1, and ROS upon UVB stress. PARP-1 not only serves DNA repair function but also orchestrates interactions to EGFR transactivation and ROS production, leading to p38 signaling for inflammatory gene expression in keratinocytes.