Potential Role of Cytosolic RNA Sensor MDA5 as an Inhibitor for Keratinocyte Differentiation in the Pathogenesis of Psoriasis

Qinzhuliangxue mixture ameliorates psoriasis by restraining apoptosis in psoriasis via downregulating the MDA-5 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Psoriasis is characterized by hyperkeratosis that produces the classic silvery scales, and the pathogenesis of psoriasis involves abnormal proliferation of keratinocytes. Emerging evidence supports that apoptosis regulates keratinocyte proliferation and formation of stratum corneum, which maintains the homeostasis of the skin. Qinzhuliangxue mixture (QZLX) is a representative formula for the treatment of psoriasis, which was earliest recorded in the classic Chinese medicine book Xia's Surgery. In our previous clinical studies, QZLX demonstrated 83.33% efficacy with few side effects in the treatment of psoriasis. Furthermore, our published basic research has also proved that the QZLX mixture effectively inhibits the hyperproliferation of keratinocytes, thus exerting therapeutic effects on psoriasis. However, whether QZLX mixture can regulate keratinocytes apoptosis requires further clarification.

OBJECTIVE OF THE STUDY

To investigate the mechanism of QZLX in the treatment of psoriasis from the perspective of keratinocyte apoptosis.

MATERIALS AND METHODS

First, psoriasis-like mice with imiquimod (IMQ)-induced were given QZLX intragastric administration and Psoriasis Area Severity Index (PASI) scores were recored for 11 consecutive days to appraise the efficacy. Then, tissue samples were collected for transcriptome analysis. The DEseq2 method detected significantly differentially expressed genes (DEGs), Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway databases were used to analyze the functions and pathway enrichment of DEGs. After that, the therapeutic mechanisms of QZLX in intervening with psoriasis were explored using TUNEL, immunohistochemical staining, and western blotting.

RESULTS

QZLX ameliorated the symptoms and pathological characteristics of IMQ-induced psoriasis in mice. The epidermal cell hyperplasia in the skin was inhibited, in accordance with the suppressed expression of PCNA and Ki67 after treatment. Transcriptome sequencing showed that melanoma differentiation associated gene-5 (MDA-5) was downregulated. GO and KEGG enrichment analysis of the signaling pathways indicated that the differentially expressed genes were significantly enriched in apoptosis pathways. Besides, QZLX treatment decreased the apoptosis of keratinocyte as shown by reduced TUNEL-positive cells. As MDA-5 protein levels decreased, so did the expression of the downstream protein Caspase-8, which indicates that the apoptotic pathway was triggered. Furthermore, QZLX therapy might also help to balance the apoptotic Bcl-2 family expression.

CONCLUSION

QZLX restrains the apoptosis of keratinocyte in psoriasis-like mice by downregulating the MDA-5 pathway. The restoration of the balance between cell apoptosis and proliferation in the skin may lead to considerable psoriasis relief. Our study reveals the possible molecular processes behind the effects of QZLX therapy on the skin lesions of psoriasis, and lends support to its clinical efficacy.

Mechanistic Investigation of WWOX Function in NF-kB-Induced Skin Inflammation in Psoriasis

Psoriasis is a chronic inflammatory skin disease characterized by epidermal hyperproliferation, aberrant differentiation of keratinocytes, and dysregulated immune responses. WW domain-containing oxidoreductase (WWOX) is a non-classical tumor suppressor gene that regulates multiple cellular processes, including proliferation, apoptosis, and migration. This study aimed to explore the possible role of WWOX in the pathogenesis of psoriasis. Immunohistochemical analysis showed that the expression of WWOX was increased in epidermal keratinocytes of both human psoriatic lesions and imiquimod-induced mice psoriatic model. Immortalized human epidermal keratinocytes were transduced with a recombinant adenovirus expressing microRNA specific for WWOX to downregulate its expression. Inflammatory responses were detected using Western blotting, real-time quantitative reverse transcription polymerase chain reaction (PCR), and enzyme-linked immunosorbent assay. In human epidermal keratinocytes, WWOX knockdown reduced nuclear factor-kappa B signaling and levels of proinflammatory cytokines induced by polyinosinic: polycytidylic acid [(poly(I:C)] in vitro. Furthermore, calcium chelator and protein kinase C (PKC) inhibitors significantly reduced poly(I:C)-induced inflammatory reactions. WWOX plays a role in the inflammatory reaction of epidermal keratinocytes by regulating calcium and PKC signaling. Targeting WWOX could be a novel therapeutic approach for psoriasis in the future.

Double-Stranded RNA Induces Mortality in an MDA5-Mediated Type I Interferonopathy Model

Gain-of-function mutations in the viral dsRNA sensor melanoma differentiation-associated protein 5 (MDA5) lead to autoimmune IFNopathies, including Singleton-Merten syndrome (SMS) and Aicardi-Goutières syndrome. However, much remains unclear regarding the mechanism of disease progression and how external factors such as infection or immune stimulation with vaccination can affect the immune response. With this aim, we generated mice with human MDA5 bearing the SMS-associated mutation R822Q (hM-R822Q). hM-R822Q transgenic (Tg) mice developed SMS-like heart fibrosis, aortic valve enlargement, and aortic calcification with a systemic IFN-stimulated gene signature resulting in the activation of the adaptive immune response. Although administration of the viral dsRNA mimic polyinosinic-polycytidylic acid [poly(I:C)] did not have remarkable effects on the cardiac phenotype, dramatic inflammation was observed in the intestines where IFN production was most elevated. Poly(I:C)-injected hM-R822Q Tg mice also developed lethal hypercytokinemia marked by massive IL-6 levels in the serum. Interrupting the IFN signaling through mitochondrial antiviral signaling protein or IFN-α/β receptor alleviated hM-R822Q-induced inflammation. Furthermore, inhibition of JAK signaling with tofacitinib reduced cytokine production and ameliorated mucosal damage, enabling the survival of poly(I:C)-injected hM-R822Q Tg mice. These findings demonstrate that the MDA5 R822Q mutant introduces a critical risk factor for uncontrollable inflammation on viral infection or vaccination.

Multifactor dimensionality reduction reveals the effect of interaction between ERAP1 and IFIH1 polymorphisms in psoriasis susceptibility genes

Background: Psoriasis is a common immune-mediated hyperproliferative skin dysfunction with known genetic predisposition. Gene-gene interaction (e.g., between HLA-C and ERAP1) in the psoriasis context has been reported in various populations. As ERAP1 has been recognized as a psoriasis susceptibility gene and plays a critical role in antigen presentation, we performed this study to identify interactions between ERAP1 and other psoriasis susceptibility gene variants. Methods: We validated psoriasis susceptibility gene variants in an independent cohort of 5,414 patients with psoriasis and 5,556 controls. Multifactor dimensionality reduction (MDR) analysis was performed to identify the interaction between variants significantly associated with psoriasis in the validation cohort and ERAP1 variants. We then conducted a meta-analysis of those variants with datasets from exome sequencing, target sequencing, and validation analyses and used MDR to identify the best gene-gene interaction model, including variants that were significant in the meta-analysis and ERAP1 variants. Results: We found that 19 of the replicated variants were identified with p < 0.05 and detected six single-nucleotide polymorphisms of psoriasis susceptibility genes in the meta-analysis. MDR analysis revealed that the best predictive model was that between the rs27044 polymorphism of ERAP1 and the rs7590692 polymorphism of IFIH1 (cross-validation consistency = 9/10, test accuracy = 0.53, odds ratio = 1.32 (95% CI, 1.09-1.59), p < 0.01). Conclusion: Our findings suggest that the interaction between ERAP1 and IFIH1 affects the development of psoriasis. This hypothesis needs to be tested in basic biological studies.