Silica's silent threat: Contributing to skin fibrosis in systemic sclerosis by targeting the HDAC4/Smad2/3 pathway.

Nowadays, silica products are widely used in daily life, especially in skin applications, which inevitably increases the risk of silica exposure in general population. However, inadequate awareness of silica's potential hazards and lack of self-protection are of concern. Systemic sclerosis (SSc) is characterized by progressive tissue fibrosis under environmental and genetic interactions. Silica exposure is considered an important causative factor for SSc, but its pathogenesis remains unclear. Within this study, we showed that lower doses of silica significantly promoted the proliferation, migration, and activation of human skin fibroblasts (HSFs) within 24 h. Silica injected subcutaneously into mice induced and exacerbated skin fibrosis. Notably, silica increased histone deacetylase-4 (HDAC4) expression by inducing its DNA hypomethylation in normal HSFs. The elevated HDAC4 expression was also confirmed in SSc HSFs. Furthermore, HDAC4 was positively correlated with Smad2/3 phosphorylation and COL1, α-SMA, and CTGF expression. The HDAC4 inhibitor LMK235 mitigated silica-induced upregulation of these factors and alleviated skin fibrosis in SSc mice. Taken together, silica induces and exacerbates skin fibrosis in SSc patients by targeting the HDAC4/Smad2/3 pathway. Our findings provide new insights for evaluating the health hazards of silica exposure and identify HDAC4 as a potential interventional target for silica-induced SSc skin fibrosis.

m6A RNA methylation: The latent string-puller in fibrosis.

Fibrosis is a pathological phenomenon characterized by the aberrant accumulation of extracellular matrix (ECM) in tissues. Fibrosis is a universally age-related disease involving that many organs and is the final stage of many chronic inflammatory diseases, which often threaten the patient's health. Undoubtedly, fibrosis has become a serious economic and health burden worldwide, However, the pathogenesis of fibrosis is complex. Further, the key molecules still remain to be unraveled. Hence, so far, there have been no effective treatments designed against the key targets of fibrosis. The methylation modification on the nitrogen atom at position 6 of adenine (m6A) is the most common mRNA modification in mammals. There is increasing evidence that m6A is actively involved in the pathogenesis of fibrosis. This review aims to highlight m6A-associated mechanisms and functions in several organic fibrosis, which implies that m6A is universal and critical for fibrosis and summarize the outlook of m6A in the treatment of fibrosis. This may light up the unknown aspects of this condition for researchers interested to explore fibrosis further.

Matrine Enhances the Antitumor Efficacy of Chidamide in CTCL by Promoting Apoptosis.

BACKGROUND: Cutaneous T-cell Lymphoma (CTCL) is a rare group of non-Hodgkin lymphoma originating from the skin, which is characterized by T-cell lymphoproliferative disorders. Chidamide, a Chinese original antineoplastic agent with independent intellectual property rights, and matrine, an extract of Chinese herbal medicine, both have been reported to exert effects on the treatment of tumors individually. However, chidamide combined with matrine has not been tested for the treatment of CTCL. METHODS: Both HH and Hut78 CTCL cell lines were treated with chidamide (0.4 µmol/L), matrine (0.6 g/L), or chidamide combined with matrine for 24, 48, and 72 h. Cell viability was estimated by MTS assay at each time point. Flow cytometry was then conducted to detect cell apoptosis. The exact mechanism of chidamide combined with matrine on CTCL cells was detected by Western blotting and further validated in xenograft models of NOD/SCID mice. RESULTS AND DISCUSSION: Compared to the single drug, chidamide combined with matrine showed a more significant effect on proliferation inhibition and apoptosis induction on CTCL cells both in vitro and in vivo. The results from the in vitro and in vivo studies suggested that matrine could enhance the anti-tumor effect of chidamide by increasing the protein expression of cleaved caspase- 3 and decreasing the expression of E-cadherin, NF-κB, p-Bad, and Bcl-2 to activate apoptosis. CONCLUSION: Our data have demonstrated chidamide combined with matrine to exhibit elevated antitumor activity in both CTCL cells and xenograft models of NOD/SCID mice, which may be a potential treatment option for CTCL.

Pyroptosis: the potential eye of the storm in adult-onset Still's disease.

Pyroptosis, a form of programmed cell death with a high pro-inflammatory effect, causes cell lysis and leads to the secretion of countless interleukin-1ß (IL-1ß) and IL-18 cytokines, resulting in a subsequent extreme inflammatory response through the caspase-1-dependent pathway or caspase-1-independent pathway. Adult-onset Still's disease (AOSD) is a systemic inflammatory disease with extensive disease manifestations and severe complications such as macrophage activation syndrome, which is characterized by high-grade inflammation and cytokine storms regulated by IL-1ß and IL-18. To date, the pathogenesis of AOSD is unclear, and the available therapy is unsatisfactory. As such, AOSD is still a challenging disease. In addition, the high inflammatory states and the increased expression of multiple pyroptosis markers in AOSD indicate that pyroptosis plays an important role in the pathogenesis of AOSD. Accordingly, this review summarizes the molecular mechanisms of pyroptosis and describes the potential role of pyroptosis in AOSD, the therapeutic practicalities of pyroptosis target drugs in AOSD, and the therapeutic blueprint of other pyroptosis target drugs.

ATRA ameliorates fibrosis by suppressing the pro-fibrotic molecule Fra2/AP-1 in systemic sclerosis.

Systemic sclerosis (SSc) is an autoimmune connective tissue disease that leads to irreversible fibrosis of the skin and the internal organs. The etiology of SSc is complex, its pathophysiology is poorly understood, and clinical therapeutic options are restricted. Thus, research into medications and targets for treating fibrosis is essential and urgent. Fos-related antigen 2 (Fra2) is a transcription factor that is a member of the activator protein-1 family. Fra2 transgenic mice were shown to have spontaneous fibrosis. All-trans retinoic acid (ATRA) is a vitamin A intermediate metabolite and ligand for the retinoic acid receptor (RAR), which possesses anti-inflammatory and anti-proliferative properties. Recent research has demonstrated that ATRA also has an anti-fibrotic effect. However, the exact mechanism is not fully understood. Interestingly, we identified potential binding sites for the transcription factor RARα to the promoter region of the FRA2 gene through JASPAR and PROMO databases. In this study, the pro-fibrotic effect of Fra2 in SSc is confirmed. SSc dermal fibroblasts and bleomycin-induced fibrotic tissues of SSc animals exhibit increased levels of Fra2. Inhibition of Fra2 expression in SSc dermal fibroblasts with Fra2 siRNA markedly decreased collagen I expression. ATRA reduced the expressions of Fra2, collagen I, and α-smooth muscle actin(α-SMA) in SSc dermal fibroblasts and bleomycin-induced fibrotic tissues of SSc mice. In addition, chromatin immunoprecipitation and dual-luciferase assays demonstrated that retinoic acid receptor RARα binds to the FRA2 promoter and modulates its transcriptional activity. ATRA decreases collagen I expression both in vivo and in vitro via the reduction of Fra2 expression. This work establishes the rationale for expanding the use of ATRA in the treatment of SSc and indicates that Fra2 can be used as an anti-fibrotic target.

Intimate intertwining of the pathogenesis of hypoxia and systemic sclerosis: A transcriptome integration analysis.

Objectives: Systemic sclerosis (SSc) is an autoimmune disease caused by various pathogenic factors, including hypoxia. Hypoxia stimulates the production of the extracellular matrix to promote fibrosis. However, the integrated function and the underlying mechanism of hypoxia in SSc are unclear. Methods: In the present study, we used Agilent SurePrint G3 Human Gene Expression v3 for the transcriptional sequencing of fibroblasts with and without hypoxia to detect differentially expressed genes (DEGs) in hypoxia. We analyzed the results with the transcriptome data of SSc lesions (GSE95065) to select the co-DEGs. Then, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed on the basis of the co-DEGs using the R package ClusterProfiler, which showed that hypoxia and cross talk of hypoxia with other pathogenic factors are involved in the pathogenesis of SSc. Furthermore, we constructed a protein-protein interaction (PPI) network of co-DEGs and screened two significant functional expression modules. Results: We identified nine hub genes (ALDH1A1, EGF, NOX4, LYN, DNTT, PTGS2, TKT, ACAA2, and ALDH3A1). These genes affect the pentose phosphate pathway, oxidative stress, and lipolysis. Conclusion: Our study provides insights into the mechanisms underlying the effects of hypoxia on SSc pathogenesis, which will help to better understand SSc pathogenesis and develop new therapeutic strategies for SSc.

Pyroptosis and Its Role in Autoimmune Disease: A Potential Therapeutic Target.

Autoimmune diseases are a group of heterogeneous diseases with diverse clinical manifestations that can be divided into systemic and organ-specific. The common etiology of autoimmune diseases is the destruction of immune tolerance and the production of autoantibodies, which attack specific tissues and/or organs in the body. The pathogenesis of autoimmune diseases is complicated, and genetic, environmental, infectious, and even psychological factors work together to cause aberrant innate and adaptive immune responses. Although the exact mechanisms are unclear, recently, excessive exacerbation of pyroptosis, as a bond between innate and adaptive immunity, has been proven to play a crucial role in the development of autoimmune disease. Pyroptosis is characterized by pore formation on cell membranes, as well as cell rupture and the excretion of intracellular contents and pro-inflammatory cytokines, such as IL-1ß and IL-18. This overactive inflammatory programmed cell death disrupts immune system homeostasis and promotes autoimmunity. This review examines the molecular structure of classical inflammasomes, including NLRP3, AIM2, and P2X7-NLRP3, as the switches of pyroptosis, and their molecular regulation mechanisms. The sophisticated pyroptosis pathways, including the canonical caspase-1-mediated pathway, the noncanonical caspase-4/5/11-mediated pathway, the emerging caspase-3-mediated pathway, and the caspase-independent pathway, are also described. We highlight the recent advances in pyroptosis in autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, Sjögren's syndrome and dermatomyositis, and attempt to identify its potential advantages as a therapeutic target or prognostic marker in these diseases.

Overexpression of OASL upregulates TET1 to induce aberrant activation of CD4+ T cells in systemic sclerosis via IRF1 signaling.

BACKGROUND: Systemic sclerosis (SSc), an autoimmune disease with unknown etiology and pathogenesis, is characterized by abnormal autoimmunity, vascular dysfunction, and progressive fibrosis of skin and organs. Studies have shown that a key factor in the pathogenesis of SSc is aberrant activation of CD4+ T cells. Our previous studies have shown that a global hypomethylation state of CD4+ T cells is closely related to aberrant activation. However, the exact mechanism of hypomethylation in CD4+T cells is not yet clear. METHODS: Illumina HiSeq 2500 Platform was used to screen differentially expressed genes and explore the role of OASL, TET1, and IRF1 in the abnormal activation of CD4+T cells in SSc. Finally, double luciferase reporter gene experiments were used to analyze the interaction between IRF1 and TET1. RESULTS: OASL overexpression could upregulate TET1 to increase the hydroxymethylation levels of CD4+ T cells and induce high expression of functional proteins (CD40L and CD70), thus promoting CD4+T cell aberrant activation. Moreover, OASL upregulated TET1 via IRF1 signaling activation, and a double luciferase reporter gene experiment revealed that IRF1 can bind to the TET1 promoter region to regulate its expression. CONCLUSIONS: OASL participates in the regulation of abnormal hypomethylation of CD4+ T cells in SSc, which implies a pivotal role for IFN signaling in the pathogenesis of SSc. Regulating DNA methylation and IFN signaling may serve as therapeutic treatments in SSc.

Nonsense Suppression Therapy: An Emerging Treatment for Hereditary Skin Diseases.

Nonsense mutations cause the premature termination of protein translation via premature termination codons (PTCs), leading to the synthesis of incomplete functional proteins and causing large numbers of genetic disorders. The emergence of nonsense suppression therapy is considered to be an effective method for the treatment of hereditary diseases, but its application in hereditary skin diseases is relatively limited. This review summarizes the current research status of nonsense suppression therapy for hereditary skin diseases, and discusses the potential opportunities and challenges of applying new technologies related to nonsense suppression therapy to dermatology. Further research is needed into the possible use of nonsense suppression therapy as a strategy for the safer and specific treatment of hereditary skin diseases.

Targeting Phosphorylation of p21-activated Kinase 1 at Thr423 Induces Cell Cycle Arrest and Apoptosis in Cutaneous T-cell Lymphoma Cells.

Cutaneous T-cell lymphoma (CTCL) represents a rare group of extranodal T-cell lymphoproliferative diseases. Due to poor clinical outcome of CTCL, there is an urgent need for new and improved therapies. A small molecule, IPA-3, which inhibits p21-activated kinase 1 (PAK1), has shown therapeutic potential in various types of malignancies. In the present study, the anti-tumor effect of IPA-3 and its underlying molecular mechanism was evaluated. High expression of phosphorylated-PAK1 (pho-PAK1) was seen in CTCL lesional skin compared to benign inflammatory dermatoses. IPA-3 could significantly inhibit the proliferation of 3 CTCL lines in a dose- and time-dependent manner. The percentage of apoptotic cells was higher in the treatment group. Further, IPA-3 treatment caused increased EGR1 protein levels and decreased apoptosis-related BCL-2 and pho-BAD protein levels. In summary, inhibition of pho-PAK1 has significant anti-tumor effects in CTCL cells and it can be explored as a future therapeutic option.

Diallyl disulphide inhibits apolipoprotein(a) expression in HepG2 cells through the MEK1-ERK1/2-ELK-1 pathway.

BACKGROUND: Lipoprotein(a) [LP(a)] is implicated as a common and independent risk factor for cardiovascular diseases. The therapeutic options currently available for reducing plasma LP(a) concentrations are limited. Diallyl disulphide (DADS), the main component of garlic, regulates lipid metabolism in hepatocytes and adipocytes through ERK1/2 signalling. This study aimed to assess the effect of DADS on apolipoprotein(a) [apo(a)] in HepG2 cells. We also determined the effects of DADS on apo(a) expression and secretion in HepG2 cells as well as the underlying mechanisms. METHODS: We examined the role of DADS on apo(a) expression in HepG2 cells by treating cell with different concentrations of DADS (10, 20, 40 and 80 µg/mL) for 24 h or treating cells with 40 µg/mL DADS for 0, 6, 12, 24 and 48 h. Then we used quantitative real-time PCR to analysis apo(a) mRNA levels, used Western blot to analysis apo(a) protein levels and used enzyme-linked immunosorbent assay to test apo(a) secreted levels. To farther determined the role of DADS, we applied Transfection of small interfering RNA to knockdown ELK-1levels and applied PD98059, a specific inhibitor of ERK1/2, to block ERK1/2 signal. RESULTS: The results show DADS inhibited apo(a) at both the mRNA and protein levels in HepG2 cells in a dose-dependent manner. DADS-mediated inhibition of apoa(a) expression in HepG2 cells was attenuated when the cells were cultured in medium containing PD98059 (ERK1/2 inhibitor) or were transfected with siRNAs against MEK1 or ELK-1. Overexpression of apo(a) yielded similar results. CONCLUSIONS: This study reveals that DADS can downregulate apo(a) expression in a dose-dependent manner via the MEK-ERK12-ELK-1 pathway.

H2 S inhibits apo(a) expression and secretion through PKCα/FXR and Akt/HNF4α pathways in HepG2 cells.

Lipoprotein(a) [Lp(a)] is a strong genetic risk factor for coronary heart diseases. However, the metabolism of this protein remains poorly understood. Efficient and specific drugs that can decrease high plasma levels of Lp(a) have not been developed yet. Hydrogen sulfide (H2 S), a member of the gas transmitter family, performs important biological actions, including protection against cardiovascular diseases and maintenance of the lipid metabolism equilibrium in hepatocytes and adipocytes. In this study, we investigated the possible molecular mechanism of H2 S that influences apolipoprotein(a) [apo(a)] biosynthesis. We also determined the effects of H2 S on apo(a) expression and secretion in HepG2 cells as well as the underlying mechanisms. Results showed that H2 S significantly inhibited the expression and secretion levels of apo(a). These effects were attenuated by the PKCα inhibitor and FXR siRNA. H2 S also reduced HNF4α expression and enhanced FXR expression. The Akt inhibitor partially reversed H2 S-induced inhibition of apo(a) and HNF4α expression and apo(a) secretion. This study reveals that H2 S suppressed apo(a) expression and secretion via the PKCα-FXR and PI3K/Akt-HNF4α pathways.

Ox-Lp(a) transiently induces HUVEC autophagy via an ROS-dependent PAPR-1-LKB1-AMPK-mTOR pathway.

Oxidised lipoprotein(a) [oxLp(a)] is considered as a more potent arteriosclerotic factor than native Lp(a). However, the molecular mechanisms underlying this potency remain unclear. Reactive oxygen species (ROS) possibly act as intracellular second messengers that participate in autophagy stimulation. In this study, the effect of oxLp(a) on endothelial cell autophagy was determined. The mechanism and effect of autophagy on endothelial cells were also investigated. Results showed that oxLp(a) could induce autophagy depending on the generation of cellular ROS. Superoxide dismutase, an antioxidant, could inhibit oxLp(a)-induced autophagy in human umbilical vascular endothelial cells. Furthermore, poly(adenosine diphosphate-ribose) polymerase-1 (PARP-1)-liver kinase B1 (LKB1)-adenosine monophosphate-activated protein kinase (AMPK)-mammalian target of rapamycin (mTOR) and LKB1-AMPK-mTOR pathways are involved in oxLp(a)-induced autophagy. These pathways are also dependent on ROS. Thus, oxLp(a) induced autophagy via LKB1-AMPK-mTOR and PAPR-1-LKB1-AMPK-mTOR pathways, which are dependent on ROS generation.

MicroRNAs: Key regulators of endothelial progenitor cell functions.

Development of cardiovascular diseases mobilises endothelial progenitor cells (EPCs) from the bone marrow to participate in vascular repair and formation of new blood vessels under both pathological and physiological conditions. Therefore, EPCs show great potential for therapeutic applications; however, the phenotypic and functional characterisation of EPCs is still difficult because controversies exist regarding their accurate definition. Growing studies have shown modest clinical benefits of EPCs; however, it is necessary to better understand the regulation of EPC functions. MicroRNAs are small, non-coding, single-stranded RNAs with regulatory activities. Results of some recent studies have found that microRNAs play an important role in regulating EPC functions. In this review, we will summarise the results of some recent studies to provide an integral picture of the role of microRNAs in the regulation of EPC functions and will discuss the therapeutic applications and the new research direction.

FGF21 increases cholesterol efflux by upregulating ABCA1 through the ERK1/2-PPARγ-LXRα pathway in THP1 macrophage-derived foam cells.

FGF21, a member of the fibroblast growth factor superfamily, is an important endogenous regulator of systemic glucose and lipid metabolism. Elevated serum FGF21 levels have been reported in subjects with coronary heart disease and carotid artery plaques. However, whether FGF21 is associated with atherosclerotic diseases remains unclear. In this study, the effects of FGF21 on cholesterol efflux in THP1 macrophage-derived foam cells and the underlying mechanisms were investigated. THP1 macrophage-derived foam cells were incubated with 0, 25, 50, 100, 200, and 400 ng/mL of FGF21 for varying time periods (0, 6, 12, and 24 h). Cholesterol efflux onto apoA-1 was assessed by high-performance liquid chromatography assays, while change in ABCA1 expression was analyzed by western blot and real-time quantitative PCR. Incubation was performed with the ERK1/2-specific inhibitor PD98059, PPARγ-specific inhibitor GW9662, and LXRα siRNA. Our results show that FGF21 promotes cholesterol efflux and ABCA1 expression in THP1 macrophage-derived foam cells in a dose- and time-dependent manner. In addition, inhibition of ERK1/2 or PPARγ, or knockdown of LXRα attenuated FGF21-mediated promotion of ABCA1 expression and cholesterol efflux. These results demonstrate that FGF21 can promote cholesterol efflux by upregulating ABCA1 through the ERK1/2-PPARγ-LXRα pathway in THP1 macrophage-derived foam cells.

FGF21 inhibits apolipoprotein(a) expression in HepG2 cells via the FGFR1-ERK1/2-Elk-1 pathway.

Lipoprotein(a) [Lp(a)] is a highly atherogenic lipoprotein, whose metabolism is poorly understood. Efficient and secure drugs that can lower elevated plasma Lp(a) concentrations are currently lacking. Fibroblast growth factor-21 (FGF-21), a member of the FGFS super family, regulates glucose and lipid metabolism in hepatocytes and adipocytes via FGFR-ERK1/2 signaling. In this study, we investigated the molecular mechanisms that influence apolipoprotein(a) [apo(a)] biosynthesis. We also determined the effects of FGF21 on HepG2 cell apo(a) expression and secretion, as well as the mechanism of FGF21 in these effects. Results showed that FGF21 inhibited apo(a) expression at both mRNA and protein levels in a dose- and time--dependent manner and then suppressed the secretion of apo(a). These effects were attenuated by PD98059 (ERK1/2 inhibitor) and Elk-1 siRNA. PD166866 (FGFR1 inhibitor) also attenuated the FGF21-mediated inhibition of apo(a) expression and inhibited ERK1/2 and Elk-1 activation. These results demonstrate that FGF21 suppresses apo(a) expression via the FGFR1-ERK1/2-Elk-1 pathway.

Interaction domains of p62: a bridge between p62 and selective autophagy.

p62 is a multidomain protein that contains different kinds of protein-protein interaction domains, including an N-terminal PB1 domain, a ZZ-type zinc finger domain, a nuclear localization signal (NLS), an export motif (NES), the LC3-interacting region (LIR), the KEAP1-interacting region (KIR), and a C-terminal Ub-associated domain (UBA). p62 is involved in the degradation of protein aggregates and cytoplasmic bodies via selective autophagy through its PB1, LIR, and UBA domains to maintain homeostasis in the cell. Moreover, NES, NLS, KIR, and ZZ domains have been found to be linked to ubiquitinated protein degradation by autophagy. Therefore, understanding the functional domains of p62 is important. In this review, we attempt to expound the mechanism of connection between p62 and selective autophagy to illustrate how the domains of p62 regulate selective autophagy, and to provide a new direction and perspective on selective autophagy research.