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The irreversible damage of renal fibrosis has been widely recognized as a critical factor in the progression of chronic kidney disease (CKD) to end-stage kidney failure. This necessitates investigation into its precise mechanisms. Dual-specificity phosphatase 1 (DUSP1), a regulator of mitogen-activated protein kinase (MAPK) pathways, is linked to diseases such as cancer and immune disorders, but its role in renal fibrosis is unclear. This study aimed to clarify the role of DUSP1 in renal fibrosis, identify the intrinsic mechanisms involved, and provide a theoretical basis for the clinical translation of a new target for renal fibrosis treatment. We characterized DUSP1 expression in kidney tissues from unilateral ureteral obstruction (UUO) mice and patients with CKD using histological analysis. We established a UUO-induced renal fibrosis model using DUSP1 knockout mice. The role and mechanism of DUSP1-mediated inhibition of renal fibrosis was evaluated both and . Finally, we performed virus-mediated gene transfer, RNA-Seq, immunohistochemistry, western blotting, and qPCR to further analyze our findings. We found that DUSP1, a crucial dephosphorylating enzyme, was remarkably reduced in renal tubular epithelial cells (RTECs) in mice and patients with CKD. This reduction was inversely correlated with kidney function and severity of renal fibrosis. DUSP1 deficiency exacerbated UUO-induced renal fibrosis in mice, whereas overexpression of DUSP 1 reduces fibrogenesis in human renal tubular epithelial (HK-2) cells treated with transforming growth factor-β1 . Mechanistically, deletion of DUSP1 promotes the nuclear translocation of Smad3, a crucial mediator of renal fibrosis, primarily through dephosphorylation at its 423/425 residue. Interestingly, we observed that DUSP1 is primarily regulated by acetylation modification, which is accompanied by an increased expression of histone deacetylase 1 (HDAC1) under UUO conditions. Furthermore, HDAC1 inhibition reversed the decrease in DUSP1 and the dephosphorylation of Smad3 in RTECs. Finally, the use of HDAC1 inhibitors or adeno-associated virus-mediated DUSP1 overexpression in RTECs significantly ameliorated UUO-induced renal injury and fibrosis. These results demonstrate that DUSP1 deficiency accelerates renal fibrosis through Smad3 nuclear translocation, modulated by HDAC1-driven acetylation. HDAC1 inhibition or DUSP1 overexpression significantly alleviated renal damage, highlighting DUSP1's therapeutic potential in combating CKD progression.

Scleroderma is a chronic fibrotic disease, where proinflammatory and profibrotic events precede collagen accumulation. MKP-1 [mitogen-activated protein kinase (MAPK) phosphatase-1] downregulates inflammatory MAPK pathways suppressing inflammation. MKP-1 also supports Th1 polarization, which could shift Th1/Th2 balance away from profibrotic Th2 profile prevalent in scleroderma. In the present study, we investigated the potential protective role of MKP-1 in scleroderma. We utilized bleomycin-induced dermal fibrosis model as a well-characterized experimental model of scleroderma. Dermal fibrosis and collagen deposition as well as the expression of inflammatory and profibrotic mediators were analyzed in the skin samples. Bleomycin-induced dermal thickness and lipodystrophy were increased in MKP-1-deficient mice. MKP-1 deficiency enhanced collagen accumulation and increased expression of collagens, 1A1 and 3A1, in the dermis. Bleomycin-treated skin from MKP-1-deficient mice also showed enhanced expression of inflammatory and profibrotic factors IL-6, TGF-β1, fibronectin-1 and YKL-40, and chemokines MCP-1, MIP-1α and MIP-2, as compared to wild-type mice. The results show, for the first time, that MKP-1 protects from bleomycin-induced dermal fibrosis, suggesting that MKP-1 favorably modifies inflammation and fibrotic processes that drive the pathogenesis of scleroderma. Compounds enhancing the expression or activity of MKP-1 could thus prevent fibrotic processes in scleroderma and possess potential as a novel immunomodulative drug.

Background MicroRNAs (miRNAs) are short non-coding regulatory RNAs that control gene expression usually producing translational repression and gene silencing. High-throughput sequencing technologies have revealed heterogeneity at length and sequence level for the majority of mature miRNAs (IsomiRs). Most isomiRs can be explained by variability in either Dicer1 or Drosha cleavage during miRNA biogenesis at 5’ or 3’ of the miRNA (trimming variants). Although isomiRs have been described in different tissues and organisms, their functional validation as modulators of gene expression remains elusive. Here we have characterized the expression and function of a highly abundant miR-101 5’-trimming variant (5’-isomiR-101). Results The analysis of small RNA sequencing data in several human tissues and cell lines indicates that 5’-isomiR-101 is ubiquitously detected and a highly abundant, especially in the brain. 5’-isomiR-101 was found in Ago-2 immunocomplexes and complementary approaches showed that 5’-isomiR-101 interacted with different members of the silencing (RISC) complex. In addition, 5’-isomiR-101 decreased the expression of five validated miR-101 targets, suggesting that it is a functional variant. Both the binding to RISC members and the degree of silencing were less efficient for 5’-isomiR-101 compared with miR-101. For some targets, both miR-101 and 5’-isomiR-101 significantly decreased protein expression with no changes in the respective mRNA levels. Although a high number of overlapping predicted targets suggest similar targeted biological pathways, a correlation analysis of the expression profiles of miR-101 variants and predicted mRNA targets in human brains at different ages, suggest specific functions for miR-101- and 5’-isomiR-101. Conclusions These results suggest that isomiRs are functional variants and further indicate that for a given miRNA, the different isomiRs may contribute to the overall effect as quantitative and qualitative fine-tuners of gene expression.

Mitogen-activated protein kinases (MAPK) such as p38 and the c-Jun N-terminal kinases (JNKs) are activated during the cellular response to stress signals. Their activity is regulated by the MAPK-phosphatase 1 (DUSP1), a key component of the anti-inflammatory response. Stress kinases are well-described elements of the response to otic injury and the otoprotective potential of JNK inhibitors is being tested in clinical trials. By contrast, there are no studies exploring the role of DUSP1 in hearing and hearing loss. Here we show that Dusp1 expression is age-regulated in the mouse cochlea. Dusp1 gene knock-out caused premature progressive hearing loss, as confirmed by auditory evoked responses in Dusp1 –/ – mice. Hearing loss correlated with cell death in hair cells, degeneration of spiral neurons and increased macrophage infiltration. Dusp1 –/ – mouse cochleae showed imbalanced redox status and dysregulated expression of cytokines. These data suggest that DUSP1 is essential for cochlear homeostasis in the response to stress during ageing.

Oxidative myofibers, also known as slow-twitch myofibers, help maintain the metabolic health of mammals, and it has been proposed that decreased numbers correlate with increased risk of obesity. The transcriptional coactivator PPARgamma coactivator 1alpha (PGC-1alpha) plays a central role in maintaining levels of oxidative myofibers in skeletal muscle. Indeed, loss of PGC-1alpha expression has been linked to a reduction in the proportion of oxidative myofibers in the skeletal muscle of obese mice. MAPK phosphatase-1 (MKP-1) is encoded by mkp-1, a stress-responsive immediate-early gene that dephosphorylates MAPKs in the nucleus. Previously we showed that mice deficient in MKP-1 have enhanced energy expenditure and are resistant to diet-induced obesity. Here we show in mice that excess dietary fat induced MKP-1 overexpression in skeletal muscle, and that this resulted in reduced p38 MAPK-mediated phosphorylation of PGC-1alpha on sites that promoted its stability. Consistent with this, MKP-1-deficient mice expressed higher levels of PGC-1alpha in skeletal muscle than did wild-type mice and were refractory to the loss of oxidative myofibers when fed a high-fat diet. Collectively, these data demonstrate an essential role for MKP-1 as a regulator of the myofiber composition of skeletal muscle and suggest a potential role for MKP-1 in metabolic syndrome.

Mitogen-activated protein kinase phosphatase (Mkp)-1 exerts its anti-inflammatory activities during Gram-negative sepsis by deactivating p38 and c-Jun N-terminal kinase (JNK). We have previously shown that Mkp-1+/+ mice, but not Mkp-1−/− mice, exhibit hypertriglyceridemia during severe sepsis. However, the regulation of hepatic lipid stores and the underlying mechanism of lipid dysregulation during sepsis remains an enigma. To understand the molecular mechanism underlying the sepsis-associated metabolic changes and the role of Mkp-1 in the process, we infected Mkp-1+/+ and Mkp-1−/− mice with Escherichia coli i.v., and assessed the effects of Mkp-1 deficiency on tissue lipid contents. We also examined the global gene expression profile in the livers via RNA-seq. We found that in the absence of E. coli infection, Mkp-1 deficiency decreased liver triglyceride levels. Upon E. coli infection, Mkp-1+/+ mice, but not Mkp-1−/− mice, developed hepatocyte ballooning and increased lipid deposition in the livers. E. coli infection caused profound changes in the gene expression profile of a large number of proteins that regulate lipid metabolism in wildtype mice, while these changes were substantially disrupted in Mkp-1−/− mice. Interestingly, in Mkp-1+/+ mice E. coli infection resulted in downregulation of genes that facilitate fatty acid synthesis but upregulation of Cd36 and Dgat2, whose protein products mediate fatty acid uptake and triglyceride synthesis, respectively. Taken together, our studies indicate that sepsis leads to a substantial change in triglyceride metabolic gene expression programs and Mkp-1 plays an important role in this process.

The dual specificity phosphatase MAPK phosphatase-1 (MKP-1) feeds back on MAP kinase signaling to regulate metabolic, inflammatory and survival responses. MKP-1 is widely expressed in the central nervous system (CNS) and induced after ischemic stress, although its function in these contexts remains unclear. Here we report that MKP-1 activated several cell death factors, including BCL2 and adenovirus E1B 19 kDa interacting protein 3, and caspases 3 and 12 culminating in apoptotic cell death in vitro . MKP-1 also exerted inhibitory effects on the bZIP transcription factor CCAAT/enhancer-binding protein (C/EBP β ), previously shown to have neuroprotective properties. These effects included reduced expression of the full-length C/EBP β variant and hypo-phosphorylation at the MEK-ERK1/2-sensitive Thr 188 site. Notably, enforced expression C/EBP β rescued cells from MKP-1-induced toxicity. Studies performed in knock-out mice indicate that the MKP-1 activity is required to exclude C/EBP β from the nucleus basally, and that MKP-1 antagonizes C/EBP β expression after global forebrain ischemia, particularly within the vulnerable CA1 sector of the hippocampus. Overall, MKP-1 appears to lower the cellular apoptotic threshold by inhibiting C/EBP β and enhancing both BH3 protein expression and cellular caspase activity. Thus, although manipulation of the MKP-1-C/EBP β axis could have therapeutic value in ischemic disorders, our observations using MKP-1 catalytic mutants suggest that approaches geared towards inhibiting MKP-1’s phosphatase activity alone may be ineffective.

IL-12 and IL-23 are produced by activated antigen-presenting cells but the two induce distinct immune responses by promoting Th1 and Th17 cell differentiation, respectively. IL-23 is a heterodimeric cytokine consisting of two subunits: p40 that is shared with IL-12 and p19 unique to IL-23. In this study, we showed that the production of IL-23 but not IL-12 was negatively regulated by protein phosphatase 2A (PP2A) in dendritic cells (DC). PP2A inhibits IL-23 production by suppressing the expression of the IL-23p19 gene. Treating DC with okadaic acid that inhibits the PP2A activity or knocking down the catalytic subunit of PP2A with siRNA enhanced IL-23 but not IL-12 production. Unlike PP2A, MAP kinase phosphatase-1 or CYLD did not show an effect on IL-23 production supporting the specificity of PP2A. PP2A-mediated inhibition requires a newly made protein that is likely responsible for bringing PP2A and IKKβ together upon LPS stimulation, which then results in the termination of IKK phosphorylation. Thus, our results uncovered an important role of the protein phosphatase in the regulation of IL-23 production and identified PP2A as a previously uncharacterized inhibitor of IL-23p19 expression in DC.

Cancer cells subvert immune surveillance through inhibition of T cell effector function. Elucidation of the mechanism of T cell dysfunction is therefore central to cancer immunotherapy. Here, we report that dual specificity phosphatase 2 (DUSP2; also known as phosphatase of activated cells 1, PAC1) acts as an immune checkpoint in T cell antitumor immunity. PAC1 is selectively upregulated in exhausted tumor-infiltrating lymphocytes and is associated with poor prognosis of patients with cancer. PAC1 hi effector T cells lose their proliferative and effector capacities and convert into exhausted T cells. Deletion of PAC1 enhances immune responses and reduces cancer susceptibility in mice. Through activation of EGR1, excessive reactive oxygen species in the tumor microenvironment induce expression of PAC1, which recruits the Mi-2β nucleosome-remodeling and histone-deacetylase complex, eventually leading to chromatin remodeling of effector T cells. Our study demonstrates that PAC1 is an epigenetic immune regulator and highlights the importance of targeting PAC1 in cancer immunotherapy. Yin and colleagues show that the phosphatase PAC1 (DUSP2) acts as a checkpoint in cytotoxic T cells to restrain their antitumor function.

Myocardial apoptosis is a cardinal process in acute viral myocarditis (VMC) instigated by coxsackievirus B3 (CVB3) infection. The anti-apoptotic regulator protein deglycase DJ-1 (DJ-1) is implicated in several pathological processes, yet its role in CVB3-induced VMC remains obscure. In this study, we decipher the protective role of DJ-1 against VMC. We found decreased DJ-1 expression in CVB3-infected H9C2 cells and VMC mouse heart tissues. DJ-1 knockout exacerbated VMC severity and apoptosis. Conversely, recovery of DJ-1 levels showed protective effects in vitro and in vivo. We observed downregulation of Dusp1 in DJ-1-deficient mice hearts and H9C2 cells with DJ-1 silencing. Subsequent in vitro assays corroborated that downregulation of DJ-1 amplifies apoptosis in H9C2 cells following CVB3 infection. This effect is mediated through the suppression of Dusp1 expression, thereby triggering the activation of the P38MAPK signaling pathway. Overall, our findings underscore DJ-1 as an appealing therapeutic target for VMC, with its anti-apoptotic effects in CVB3-induced VMC mediated in part via the Dusp1/P38MAPK signaling pathway. This novel understanding of DJ-1’s regulation might provide fresh insights into the pathogenesis of VMC and a potential therapeutic avenue for VMC.