MCPIP-1, Alias Regnase-1, Controls Epithelial Inflammation by Posttranscriptional Regulation of IL-8 Production

Regnase-1 overexpression as a therapeutic approach of Marfan syndrome

Rupture or dissection of thoracic aortic aneurysms is still the leading cause of death for patients diagnosed with Marfan syndrome. Inflammation and matrix digestion regulated by matrix metalloproteases (MMPs) play a major role in the pathological remodeling of the aortic media. Regnase-1 is an endoribonuclease shown to cleave the mRNA of proinflammatory cytokines, such as interleukin-6. Considering the major anti-inflammatory effects of regnase-1, here, we aimed to determine whether adeno-associated virus (AAV)-mediated vascular overexpression of the protein could provide protection from the development and progression of aortic aneurysms in Marfan syndrome. The overexpression of regnase-1 resulted in a marked decrease in inflammatory parameters and elastin degradation in aortic smooth muscle cells in vitro. Intravenous injection of a vascular-targeted AAV vector resulted in the efficient transduction of the aortic wall and overexpression of regnase-1 in a murine model of Marfan syndrome, associated with lower circulating levels of proinflammatory cytokines and decreased MMP expression and activity. Regnase-1 overexpression strongly improved elastin architecture in the media and reduced aortic diameter at distinct locations. Therefore, AAV-mediated regnase-1 overexpression may represent a novel gene therapy approach for inhibiting aortic aneurysms in Marfan syndrome.

Let-7g Upregulation Attenuated the KRAS-PI3K-Rac1-Akt Axis-Mediated Bioenergetic Functions

The aberrant activation of signaling pathways contributes to cancer cells with metabolic reprogramming. Thus, targeting signaling modulators is considered a potential therapeutic strategy for cancer. Subcellular fractionation, coimmunoprecipitation, biochemical analysis, and gene manipulation experiments revealed that decreasing the interaction of kirsten rat sarcoma viral oncogene homolog (KRAS) with p110α in lipid rafts with the use of naringenin (NGN), a citrus flavonoid, causes lipid raft-associated phosphatidylinositol 3-kinase (PI3K)-GTP-ras-related C3 botulinum toxin substrate 1 (Rac1)-protein kinase B (Akt)-regulated metabolic dysfunction of glycolysis and mitochondrial oxidative phosphorylation (OXPHOS), leading to apoptosis in human nasopharyngeal carcinoma (NPC) cells. The use of lethal-7g (let-7g) mimic and let-7g inhibitor confirmed that elevated let-7g resulted in a decrease in KRAS expression, which attenuated the PI3K-Rac1-Akt-BCL-2/BCL-xL-modulated mitochondrial energy metabolic functions. Increased let-7g depends on the suppression of the RNA-specificity of monocyte chemoattractant protein-induced protein-1 (MCPIP1) ribonuclease since NGN specifically blocks the degradation of pre-let-7g by NPC cell-derived immunoprecipitated MCPIP1. Converging lines of evidence indicate that the inhibition of MCPIP1 by NGN leads to let-7g upregulation, suppressing oncogenic KRAS-modulated PI3K-Rac1-Akt signaling and thereby impeding the metabolic activities of aerobic glycolysis and mitochondrial OXPHOS.

Localization and expression profiles of gingival monocyte chemoattractant protein-1-induced protein-1 (MCPIP-1) and mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT-1)

OBJECTIVES

The purposes of this study were to localize monocyte chemoattractant protein-1-induced protein-1 (MCPIP-1) and its suppressor mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT-1) in gingival tissues and to profile their protein expression levels in relation to the clinical inflammation, Porphyromonas gingivalis colonization, and interleukin (IL)-8 levels.

MATERIALS AND METHODS

Study samples were collected from two independent study populations: (1) Gingival tissues were collected from eight periodontally healthy individuals and eight periodontitis patients to localize MCPIP-1 and MALT-1 immunohistochemically, and (2) forty-one gingival tissue samples with marginal, mild, or moderate to severe inflammation were collected from 20 periodontitis patients to determine MCPIP-1 and MALT-1 levels using immunoblots, P. gingivalis levels with qPCR, P. gingivalis gingipain activities with fluorogenic substrates, and IL-8 levels with multiplex technique.

RESULTS

MCPIP-1 was detectable in the epithelium and in connective tissue, being especially prominent around the blood vessel walls in healthy periodontal tissues. MALT-1 was observed at all layers of gingival epithelium and especially around the accumulated inflammatory cells in connective tissue. No difference in gingival tissue MCPIP-1 and MALT-1 levels was observed in relation to the severity of gingival inflammation. MALT-1 levels were elevated (p = 0.023) with the increase in tissue P. gingivalis levels, and there was an association between MALT-1 and IL-8 levels (β = 0.054, p = 0.001).

CONCLUSIONS

Interactions of MALT-1 levels with gingival tissue P. gingivalis counts and IL-8 levels suggest that activation of MALT-1 can take part in P. gingivalis-regulated host immune responses.

CLINICAL RELEVANCE

Pharmacological targeting the crosstalk between immune response and MCPIP-1/MALT-1 may have benefits in periodontal treatment.

Hepatic MCPIP1 protein levels are reduced in NAFLD patients and are predominantly expressed in cholangiocytes and liver endothelium

BACKGROUND AND AIMS

NAFLD is characterized by the excessive accumulation of fat in hepatocytes. NAFLD can range from simple steatosis to the aggressive form called NASH, which is characterized by both fatty liver and liver inflammation. Without proper treatment, NAFLD may further progress to life-threatening complications, such as fibrosis, cirrhosis, or liver failure. Monocyte chemoattractant protein-induced protein 1 (MCPIP1, alias Regnase 1) is a negative regulator of inflammation, acting through the cleavage of transcripts coding for proinflammatory cytokines and the inhibition of NF-κB activity.

METHODS

In this study, we investigated MCPIP1 expression in the liver and peripheral blood mononuclear cells (PBMCs) collected from a cohort of 36 control and NAFLD patients hospitalized due to bariatric surgery or primary inguinal hernia laparoscopic repair. Based on liver histology data (hematoxylin and eosin and Oil Red-O staining), 12 patients were classified into the NAFL group, 19 into the NASH group, and 5 into the control (non-NAFLD) group. Biochemical characterization of patient plasma was followed by expression analysis of genes regulating inflammation and lipid metabolism. The MCPIP1 protein level was reduced in the livers of NAFL and NASH patients in comparison to non-NAFLD control individuals. In addition, in all groups of patients, immunohistochemical staining showed that the expression of MCPIP1 was higher in the portal fields and bile ducts in comparison to the liver parenchyma and central vein. The liver MCPIP1 protein level negatively correlated with hepatic steatosis but not with patient body mass index or any other analyte. The MCPIP1 level in PBMCs did not differ between NAFLD patients and control patients. Similarly, in patients' PBMCs there were no differences in the expression of genes regulating β-oxidation (ACOX1, CPT1A, and ACC1) and inflammation (TNF, IL1B, IL6, IL8, IL10, and CCL2), or transcription factors controlling metabolism (FAS, LCN2, CEBPB, SREBP1, PPARA, and PPARG).

CONCLUSION

We have demonstrated that MCPIP1 protein levels are reduced in NAFLD patients, but further research is needed to investigate the specific role of MCPIP1 in NAFL initiation and the transition to NASH.

MCPIP1 alleviated alcohol-induced immune dysfunction via the MAPK/ERK signaling pathway

RATIONALE

In recent years, monocyte chemotactic protein-induced protein 1 (MCPIP1) has been reported to control inflammation via IL-10.

OBJECTIVES

The aims of this study were to determine (1) whether MCPIP1 can repair damage to the immune system after alcohol use and (2) whether MCPIP1 can repair the immune function impaired by alcohol use through the MAPK/ERK signaling pathway. Our results will inform the treatment of immune dysfunction caused by alcohol consumption.

METHODS

Scrambled shRNA or MCPIP-1-shRNA carried by the lentiviral vector (50μl each at 1×108TU/ml) was injected retrogradely through the pancreatic duct to pretreat male C57BL/6 mice. Five days after the injection, mice were exposed to intragastric ethanol infusion (5g/kg, 25% ethanol w/v) daily or vehicle for 10 days.

RESULTS

MCPIP-1 protein was increased in the pancreas after alcohol exposure. MCPIP-1 shRNA specifically decreased MCPIP-1 protein expression and mRNA level in the pancreas. Specific knockdown of MCPIP-1 exacerbates pancreatic necrosis, interstitial edema, and inflammatory infiltrates after alcohol exposure. Meanwhile, specific knockdown of MCPIP-1 also increased pancreatic pro-inflammatory cytokine (IL-6 and IL-1β), chemokine MCP-1, and chemokine receptor 2 (CCR2) after alcohol exposure. What's more, p-JNK and p-ERK in the pancreas were all similarly increased in response to pancreas-specific knockdown of MCPIP-1 during alcohol exposure.

CONCLUSIONS

Taken together, the results above suggested that MCPIP1 repairs the immune function impaired by alcohol use via stimulating JNK and ERK pathways. Our results will inform the treatment of immune dysfunction caused by alcohol consumption.

Differential Expression of Anti-Inflammatory RNA Binding Proteins in Lupus Nephritis

Lupus nephritis (LN) is a type of immunological complex glomerulonephritis characterized by chronic renal inflammation which is exacerbated by infiltrating leukocytes and fueled by a variety of pro-inflammatory cytokines. A profound understanding of the pathogenesis of LN is necessary to identify the optimal molecular targets. The role of RNA-binding proteins (RBPs) in post-transcriptional gene regulation in the immune system is being explored in greater depth to better understand how this regulation is implicated in inflammatory and autoimmune diseases. Tristetraprolin (TTP), Roquin-1/2, and Regnase-1 are 3 RBPs that play a critical role in the regulation of pro-inflammatory mediators by gating the degradation and/or translational silencing of target mRNAs. In this study, we proposed to focus on the differential expression of these RBPs in immune cells and renal biopsies from LN patients, as well as their regulatory impact on a specific target. Herein, we highlight a novel target of anti-inflammatory treatment by revealing the mechanisms underlying RBP expression and the interaction between RBPs and their target RNAs.

Resistance to tyrosine kinase inhibitors promotes renal cancer progression through MCPIP1 tumor-suppressor downregulation and c-Met activation

Tyrosine kinase inhibitors (TKIs) are the most commonly used targeted therapeutics in clear-cell renal cell carcinoma (ccRCC); however, drug resistance limits their utility and can lead to tumor "flare-up" and progression. In this study, we show that RCC resistance to sunitinib and sorafenib involves different mechanisms and leads to increased malignancy. Sunitinib decreased tumor growth and cell motility along with increased E-cadherin expression and secretion of the proangiogenic cytokines IL6 and IL8, which activated senescence in ccRCC cells and led to VE-cadherin phosphorylation, enhancing tumor angiogenesis. Sorafenib resistance increased the levels of mesenchymal markers and the secretion of MMP9, which cleaved VE-cadherin and disrupted endothelial cell integrity. Both sunitinib resistance and sorafenib resistance led to activation of the c-Met receptor IRAK1 and downregulation of the tumor suppressor MCPIP1, resulting in an increase in the metastasis of resistant cells, possibly due in part to enhanced vascularization of ccRCC. MCPIP1 overexpression partially overcame resistance to these drugs by decreasing micrometastasis and decreasing the expression of factors involved in tumorigenesis. In tumor samples from ccRCC patients, we observed a significant increase in the level of the c-Met receptor, IRAK1 and a decrease in MCPIP1 with respect to normal kidney tissue. Our results indicate separate novel mechanisms for sunitinib and sorafenib resistance, which both lead to MCPIP1 inhibition and ccRCC progression. The presented study suggests caution in the treatment of RCC with TKIs, which may lead to the unintended outcome of tumor progression.

MCPIP1 promotes cell proliferation, migration and angiogenesis of glioma via VEGFA-mediated ERK pathway

Glioma is the most common primary malignant intracranial tumor in the population, and is often associated with abundant angiogenesis. However, how angiogenesis is regulated during glioma progression is still poorly understood. Data mining of cancer patient database shows that MCPIP1 is positively correlated with VEGFA expression and negatively with survival. In this study, we report that overexpressed MCPIP1 in glioma cells is a boost of angiogenesis. Mechanistically, MCPIP1 upregulates the expression of VEGFA in glioma, and promote the secretion of VEGFA to the surroundings, which could stimulate angiogenesis through ERK pathway. Blocking VEGFA expression and secretion inhibited MCPIP1-mediated angiogenesis and glioma progression in vitro and xenograft models. Collectively, these results identify a critical role for MCPIP1 in angiogenesis and glioma progression by regulating the VEGFA-mediated ERK pathway, suggesting that targeting MCPIP1 may be a potential glioma-selective therapeutic strategy.

Macrophage-Specific MCPIP1/Regnase-1 Attenuates Kidney Ischemia-Reperfusion Injury by Shaping the Local Inflammatory Response and Tissue Regeneration

Sterile inflammation either resolves the initial insult or leads to tissue damage. Kidney ischemia/reperfusion injury (IRI) is associated with neutrophilic infiltration, enhanced production of inflammatory mediators, accumulation of necrotic cells and tissue remodeling. Macrophage-dependent microenvironmental changes orchestrate many features of the immune response and tissue regeneration. The activation status of macrophages is influenced by extracellular signals, the duration and intensity of the stimulation, as well as various regulatory molecules. The role of macrophage-derived monocyte chemoattractant protein-induced protein 1 (MCPIP1), also known as Regnase-1, in kidney ischemia-reperfusion injury (IRI) and recovery from sterile inflammation remains unresolved. In this study, we showed that macrophage-specific Mcpip1 deletion significantly affects the kidney phenotype. Macrophage-specific Mcpip1 transgenic mice displayed enhanced inflammation and loss of the tubular compartment upon IRI. We showed that MCPIP1 modulates sterile inflammation by negative regulation of Irf4 expression and accumulation of IRF4+ cells in the tissue and, consequently, suppresses the post-ischemic kidney immune response. Thus, we identified MCPIP1 as an important molecular sentinel of immune homeostasis in experimental acute kidney injury (AKI) and renal fibrosis.

Shaping the Innate Immune Response Through Post-Transcriptional Regulation of Gene Expression Mediated by RNA-Binding Proteins

Innate immunity is the frontline of defense against infections and tissue damage. It is a fast and semi-specific response involving a myriad of processes essential for protecting the organism. These reactions promote the clearance of danger by activating, among others, an inflammatory response, the complement cascade and by recruiting the adaptive immunity. Any disequilibrium in this functional balance can lead to either inflammation-mediated tissue damage or defense inefficiency. A dynamic and coordinated gene expression program lies at the heart of the innate immune response. This expression program varies depending on the cell-type and the specific danger signal encountered by the cell and involves multiple layers of regulation. While these are achieved mainly via transcriptional control of gene expression, numerous post-transcriptional regulatory pathways involving RNA-binding proteins (RBPs) and other effectors play a critical role in its fine-tuning. Alternative splicing, translational control and mRNA stability have been shown to be tightly regulated during the innate immune response and participate in modulating gene expression in a global or gene specific manner. More recently, microRNAs assisting RBPs and post-transcriptional modification of RNA bases are also emerging as essential players of the innate immune process. In this review, we highlight the numerous roles played by specific RNA-binding effectors in mediating post-transcriptional control of gene expression to shape innate immunity.

PIN and CCCH Zn-finger domains coordinate RNA targeting in ZC3H12 family endoribonucleases

The CCCH-type zinc finger (ZnF) containing ZC3H12 ribonucleases are crucial in post-transcriptional immune homoeostasis with ZC3H12A being the only structurally studied member of the family. In this study, we present a structural-biochemical characterization of ZC3H12C, which is linked with chronic immune disorders like psoriasis. We established that the RNA substrate is cooperatively recognized by the PIN and ZnF domains of ZC3H12C and analyzed the crystal structure of ZC3H12C bound to a single-stranded RNA substrate. The RNA engages in hydrogen-bonded contacts and stacking interactions with the PIN and ZnF domains simultaneously. The ZC3H12 ZnF shows unprecedented structural features not previously observed in any member of the CCCH-ZnF family and utilizes stacking interactions via a unique combination of spatially conserved aromatic residues to align the target transcript in a bent conformation onto the ZnF scaffold. Further comparative structural analysis of ZC3H12 CCCH-ZnF suggests that a trinucleotide sequence is recognized by ZC3H12 ZnF in target RNA. Our work not only describes the initial structure-biochemical study on ZC3H12C, but also provides the first molecular insight into RNA recognition by a ZC3H12 family member. Finally, our work points to an evolutionary code for RNA recognition adopted by CCCH-type ZnF proteins.

Subversion of Lipopolysaccharide Signaling in Gingival Keratinocytes via MCPIP-1 Degradation as a Novel Pathogenic Strategy of Inflammophilic Pathobionts

Periodontal disease (PD) is an inflammatory disease of the supporting tissues of the teeth that develops in response to formation of a dysbiotic biofilm on the subgingival tooth surface. Although exacerbated inflammation leads to alveolar bone destruction and may cause tooth loss, the molecular basis of PD initiation and progression remains elusive. Control over the inflammatory reaction and return to homeostasis can be efficiently restored by negative regulators of Toll-like receptor (TLR) signaling pathways such as monocyte chemoattractant protein-induced protein 1 (MCPIP-1), which is constitutively expressed in gingival keratinocytes and prevents hyperresponsiveness in the gingiva. Here, we found that inflammophilic periodontal species influence the stability of MCPIP-1, leading to an aggravated response of the epithelium to proinflammatory stimulation. Among enzymes secreted by periodontal species, gingipains—cysteine proteases from Porphyromonas gingivalis—are considered major contributors to the pathogenic potential of bacteria, strongly influencing the components of the innate and adaptive immune system. Gingipain proteolytic activity leads to a rapid degradation of MCPIP-1, exacerbating the inflammatory response induced by endotoxin. Collectively, these results establish a novel mechanism of corruption of inflammatory signaling by periodontal pathogens, indicating new possibilities for treatment of this chronic disease.

Multifunctional RNase MCPIP1 and its Role in Cardiovascular Diseases

Monocyte chemoattractant protein-1 induced protein 1 (MCPIP1), one of the MCPIP family members, is characterized by the presence of both C-x8-C-x5-C-x3-H (CCCH)- type zinc finger and PilT-N-terminal domains. As a potent regulator of innate immunity, MCPIP1 exerts anti-inflammatory effects through its ribonuclease (RNase) and deubiquitinating enzyme activities to degrade cytokine mRNAs and inhibit nuclear factor- kappa B (NF-κB), respectively. MCPIP1 is expressed not only in immune cells but also in many other cell types, including cardiomyocytes, vascular endothelial cells (ECs) and smooth muscle cells (SMCs). Increasing evidence indicates that MCPIP1 plays a role in the regulation of cardiac functions and is involved in the processes of vascular diseases, such as ischemia-reperfusion (I/R) and atherosclerosis. To better understand the emerging roles of MCPIP1 in the cardiovascular system, we reviewed the current literature with respect to MCPIP1 functions and discussed its association with the pathogenesis of cardiovascular diseases and the implication as a therapeutic target.

Role of Mcpip1 in obesity-induced hepatic steatosis as determined by myeloid and liver-specific conditional knockouts

Monocyte chemoattractant protein-induced protein 1 (MCPIP1, alias Regnase 1) is a negative regulator of inflammation, acting through cleavage of transcripts coding for proinflammatory cytokines and by inhibition of NFκB activity. Moreover, it was demonstrated that MCPIP1 regulates lipid metabolism both in adipose tissue and in hepatocytes. In this study, we investigated the effects of tissue-specific Mcpip1 deletion on the regulation of hepatic metabolism and development of nonalcoholic fatty liver disease (NAFLD). We used control Mcpip1^fl/fl mice and animals with deletion of Mcpip1 in myeloid leukocytes (Mcpip1^fl/fl LysM^Cre ) and in hepatocytes (Mcpip1^fl/fl Alb^Cre ), which were fed chow or a high-fat diet (HFD) for 12 weeks. Mcpip1^fl/fl LysM^Cre mice fed a chow diet were characterized by a significantly reduced hepatic expression of genes regulating lipid and glucose metabolism, which subsequently resulted in low plasma glucose level and dyslipidemia. These animals also displayed systemic inflammation, demonstrated by increased concentrations of cytokines in the plasma and high Tnfa, Il6, IL1b mRNA levels in the liver and brown adipose tissue (BAT). Proinflammatory leukocyte infiltration into BAT, together with low expression of Ucp1 and Ppargc1a, resulted in hypothermia of 22-week-old Mcpip1^fl/fl LysM^Cre mice. On the other hand, there were no significant changes in phenotype in Mcpip1^fl/fl Alb^Cre mice. Although we detected a reduced hepatic expression of genes regulating glucose metabolism and β-oxidation in these mice, they remained asymptomatic. Upon feeding with a HFD, Mcpip1^fl/fl LysM^Cre mice did not develop obesity, glucose intolerance, nor hepatic steatosis, but were characterized by low plasma glucose level and dyslipidemia, along with proinflammatory phenotype. Mcpip1^fl/fl Alb^Cre animals, following a HFD, became hypercholesterolemic, but accumulated lipids in the liver at the same level as Mcpip1^fl/fl mice, and no changes in the level of soluble factors tested in the plasma were detected. We have demonstrated that Mcpip1 protein plays an important role in the liver homeostasis. Depletion of Mcpip1 in myeloid leukocytes, followed by systemic inflammation, has a more pronounced effect on controlling liver metabolism and homeostasis than the depletion of Mcpip1 in hepatocytes.

Repression of transcription by the glucocorticoid receptor: A parsimonious model for the genomics era

Glucocorticoids are potent anti-inflammatory drugs that are used to treat an extraordinary range of human disease, including COVID-19, underscoring the ongoing importance of understanding their molecular mechanisms. Early studies of GR signaling led to broad acceptance of models in which glucocorticoid receptor (GR) monomers tether repressively to inflammatory transcription factors, thus abrogating inflammatory gene expression. However, newer data challenge this core concept and present an exciting opportunity to reframe our understanding of GR signaling. Here, we present an alternate, two-part model for transcriptional repression by glucocorticoids. First, widespread GR-mediated induction of transcription results in rapid, primary repression of inflammatory gene transcription and associated enhancers through competition-based mechanisms. Second, a subset of GR-induced genes, including targets that are regulated in coordination with inflammatory transcription factors such as NF-κB, exerts secondary repressive effects on inflammatory gene expression. Within this framework, emerging data indicate that the gene set regulated through the cooperative convergence of GR and NF-κB signaling is central to the broad clinical effectiveness of glucocorticoids in terminating inflammation and promoting tissue repair.

Murine myeloid cell MCPIP1 suppresses autoimmunity by regulating B-cell expansion and differentiation

Myeloid-derived cells, in particular macrophages, are increasingly recognized as critical regulators of the balance of immunity and tolerance. However, whether they initiate autoimmune disease or perpetuate disease progression in terms of epiphenomena remains undefined.Here, we show that depletion of MCPIP1 in macrophages and granulocytes (Mcpip1fl/fl-LysMcre+ C57BL/6 mice) is sufficient to trigger severe autoimmune disease. This was evidenced by the expansion of B cells and plasma cells and spontaneous production of autoantibodies, including anti-dsDNA, anti-Smith and anti-histone antibodies. Consequently, we document evidence of severe skin inflammation, pneumonitis and histopathologic evidence of glomerular IgG deposits alongside mesangioproliferative nephritis in 6-month-old mice. These phenomena are related to systemic autoinflammation, which secondarily induces a set of cytokines such as Baff, Il5, Il9 and Cd40L, affecting adaptive immune responses. Therefore, abnormal macrophage activation is a key factor involved in the loss of immune tolerance.Overall, we demonstrate that deficiency of MCPIP1 solely in myeloid cells triggers systemic lupus-like autoimmunity and that the control of myeloid cell activation is a crucial checkpoint in the development of systemic autoimmunity.

MCPIP-1 Restricts Inflammation via Promoting Apoptosis of Neutrophils

Monocyte chemoattractant protein-induced protein-1 (MCPIP-1) is a potent inhibitor of inflammatory response to pathogens. Acting as endonuclease against transcripts of inflammatory cytokines or transcription factors MCPIP-1 can significantly reduce the cytokine storm, thus limiting the tissue damage. As the adequate resolution of inflammation depends also on the efficient clearance of accumulated neutrophils, we focused on the role of MCPIP-1 in apoptosis and retention of neutrophils. We used peritoneal neutrophils from cell-specific MCPIP-1 knockout mice and showed prolonged survival of these cells. Moreover, we confirmed that MCPIP-1-dependent degradation of transcripts of antiapoptotic genes, including BCL3, BCL2A1, BCL2L1, and for the first time MCL-1, serves as an early event in spontaneous apoptosis of primary neutrophils. Additionally, we identified previously unknown miRNAs as potential binding partners to the MCPIP-1 transcript and their regulation suggest a role in MCPIP-1 half-life and translation. These phenomena may play a role as a molecular switch that balances the MCPIP-1-dependent apoptosis. Besides that, we determined these particular miRNAs as integral components of the GM-CSF-MCPIP-1 axis. Taken together, we identified the novel anti-inflammatory role of MCPIP-1 as a regulator of accumulation and survival of neutrophils that simultaneously promotes an adequate resolution of inflammation.

Deletion of Mcpip1 in Mcpip1fl/flAlbCre mice recapitulates the phenotype of human primary biliary cholangitis

Primary biliary cholangitis (PBC) is an autoimmune disease characterized by progressive destruction of the intrahepatic bile ducts. The immunopathology of PBC involves excessive inflammation; therefore, negative regulators of inflammatory response, such as Monocyte Chemoattractant Protein-1-Induced Protein-1 (MCPIP1) may play important roles in the development of PBC. The aim of this work was to verify whether Mcpip1 expression protects against development of PBC. Genetic deletion of Zc3h12a was used to characterize the role of Mcpip1 in the pathogenesis of PBC in 6–52-week-old mice. We found that Mcpip1 deficiency in the liver (Mcpip1^fl/flAlb^Cre) recapitulates most of the features of human PBC, in contrast to mice with Mcpip1 deficiency in myeloid cells (Mcpip1^fl/flLysM^Cre mice), which present with robust myeloid cell-driven systemic inflammation. In Mcpip1^fl/flAlb^Cre livers, intrahepatic bile ducts displayed proliferative changes with inflammatory infiltration, bile duct destruction, and fibrosis leading to cholestasis. In plasma, increased concentrations of IgG, IgM, and AMA autoantibodies (anti-PDC-E2) were detected. Interestingly, the phenotype of Mcpip1^fl/flAlb^Cre mice was robust in 6-week-old, but milder in 12–24-week-old mice. Hepatic transcriptome analysis of 6-week-old and 24-week-old Mcpip1^fl/flAlb^Cre mice showed 812 and 8 differentially expressed genes, respectively, compared with age-matched control mice, and revealed a distinct set of genes compared to those previously associated with development of PBC. In conclusion, Mcpip1^fl/flAlb^Cre mice display early postnatal phenotype that recapitulates most of the features of human PBC.

MCPIP1 inhibits Wnt/β-catenin signaling pathway activity and modulates epithelial-mesenchymal transition during clear cell renal cell carcinoma progression by targeting miRNAs

Epithelial-mesenchymal transition (EMT) refers to the acquisition of mesenchymal properties in cells participating in tumor progression. One hallmark of EMT is the increased level of active β-catenin, which can trigger the transcription of Wnt-specific genes responsible for the control of cell fate. We investigated how Monocyte Chemotactic Protein-1-Induced Protein-1 (MCPIP1), a negative regulator of inflammatory processes, affects EMT in a clear cell renal cell carcinoma (ccRCC) cell line, patient tumor tissues and a xenotransplant model. We showed that MCPIP1 degrades miRNAs via its RNase activity and thus protects the mRNA transcripts of negative regulators of the Wnt/β-catenin pathway from degradation, which in turn prevents EMT. Mechanistically, the loss of MCPIP1 RNase activity led to the upregulation of miRNA-519a-3p, miRNA-519b-3p, and miRNA-520c-3p, which inhibited the expression of Wnt pathway inhibitors (SFRP4, KREMEN1, CXXC4, CSNK1A1 and ZNFR3). Thus, the level of active nuclear β-catenin was increased, leading to increased levels of EMT inducers (SNAI1, SNAI2, ZEB1 and TWIST) and, consequently, decreased expression of E-cadherin, increased expression of mesenchymal markers, and acquisition of the mesenchymal phenotype. This study revealed that MCPIP1 may act as a tumor suppressor that prevents EMT by stabilizing Wnt inhibitors and decreasing the levels of active β-catenin and EMT inducers.

How are MCPIP1 and cytokines mutually regulated in cancer-related immunity?

Cytokines are secreted by various cell types and act as critical mediators in many physiological processes, including immune response and tumor progression. Cytokines production is precisely and timely regulated by multiple mechanisms at different levels, ranging from transcriptional to post-transcriptional and posttranslational processes. Monocyte chemoattractant protein-1 induced protein 1 (MCPIP1), a potent immunosuppressive protein, was first described as a transcription factor in monocytes treated with monocyte chemoattractant protein-1 (MCP-1) and subsequently found to possess intrinsic RNase and deubiquitinase activities. MCPIP1 tightly regulates cytokines expression via various functions. Furthermore, cytokines such as interleukin 1 beta (IL-1B) and MCP-1 and inflammatory cytokines inducer lipopolysaccharide (LPS) strongly induce MCPIP1 expression. Mutually regulated MCPIP1 and cytokines form a complicated network in the tumor environment. In this review, we summarize how MCPIP1 and cytokines reciprocally interact and elucidate the effect of the network formed by these components in cancer-related immunity with aim of exploring potential clinical benefits of their mutual regulation.

MCPIP1 RNase and Its Multifaceted Role

Inflammation is an organism’s physiological response to harmful septic and aseptic stimuli. This process begins locally through the influx of immune system cells to the damaged tissue and the subsequent activation and secretion of inflammatory mediators to restore homeostasis in the organism. Inflammation is regulated at many levels, and one of these levels is post-transcriptional regulation, which controls the half-life of transcripts that encode inflammatory mediators. One of the proteins responsible for controlling the amount of mRNA in a cell is the RNase monocyte chemoattractant protein-induced protein 1 (MCPIP1). The studies conducted so far have shown that MCPIP1 is involved not only in the regulation of inflammation but also in many other physiological and pathological processes. This paper provides a summary of the information on the role of MCPIP1 in adipogenesis, angiogenesis, cell differentiation, cancer, and skin inflammation obtained to date.

MCP-induced protein 1 attenuates sepsis-induced acute lung injury by modulating macrophage polarization via the JNK/c-Myc pathway

Sepsis is a potentially fatal systemic inflammatory response syndrome caused by infection. In this study, we evaluated the effects of MCP-induced protein 1 (MCPIP1), a recently discovered inflammation-related ribonuclease, on sepsis-induced acute lung injury (ALI) and investigated the underlying mechanisms. Cecal ligation puncture and lipopolysaccharide induction were performed on Sprague-Dawley rats and RAW264.7 cells, respectively, to establish sepsis-induced ALI models. The proteasome inhibitor MG132 used as an activator of MCPIP1 overexpression, and we showed that MG132 can indeed increase the expression of MCPIP1. MCPIP1 overexpression induced by MG132 alleviated sepsis-induced pathologic changes, water content and protein leakage in the lungs, and induction of systemic inflammatory mediators, and improved the 7-day mortality rate in the model rats. We also showed that MCPIP1 p showed romoted macrophage polarization from the M1 to the M2 type in sepsis-induced ALI. Furthermore, MCPIP1-enhanced M2 polarization was inhibited by an MCPIP1-targeting small interfering RNA (siMCPIP1) in RAW264.7 cells. Further mechanistic studies showed that the promotive effect of MCPIP1 on M2 polarization was related to the inhibition of c-Jun N-terminal kinase (JNK) and its downstream transcription factor c-Myc in the in vitro model. Conversely, siMCPIP1 transfection resulted in the recovery of JNK and c-Myc expression in LPS-treated cells. Taken together, these findings indicate that MCPIP1 plays a protective role in sepsis-induced ALI by modulating macrophage polarization through inhibition of the JNK/c-Myc signaling pathway. Our study presents a potentially novel therapeutic strategy for the treatment of lung injury involving the inflammatory cascade.

Drosophila Regnase-1 RNase is required for mRNA and miRNA profile remodelling during larva-to-adult metamorphosis

Metamorphosis is an intricate developmental process in which large-scale remodelling of mRNA and microRNA (miRNA) profiles leads to orchestrated tissue remodelling and organogenesis. Whether, which, and how, ribonucleases (RNases) are involved in the RNA profile remodelling during metamorphosis remain unknown. Human Regnase-1 (also known as MCPIP1 and Zc3h12a) RNase remodels RNA profile by cleaving specific RNAs and is a crucial modulator of immune-inflammatory and cellular defence. Here, we studied Drosophila CG10889, which we named Drosophila Regnase-1, an ortholog of human Regnase-1. The larva-to-adult metamorphosis in Drosophila includes two major transitions, larva-to-pupa and pupa-to-adult. regnase-1 knockout flies developed until the pupa stage but could not complete pupa-to-adult transition, dying in puparium case. Regnase-1 RNase activity is required for completion of pupa-to-adult transition as transgenic expression of wild-type Drosophila Regnase-1, but not the RNase catalytic-dead mutants, rescued the pupa-to-adult transition in regnase-1 knockout. High-throughput RNA sequencing revealed that regnase-1 knockout flies fail to remodel mRNA and miRNA profiles during the larva-to-pupa transition. Thus, we uncovered the roles of Drosophila Regnase-1 in the larva-to-adult metamorphosis and large-scale remodelling of mRNA and miRNA profiles during this metamorphosis process.

MCPIP1 regulates the sensitivity of pancreatic beta-cells to cytokine toxicity

The autoimmune-mediated beta-cell death in type 1 diabetes (T1DM) is associated with local inflammation (insulitis). We examined the role of MCPIP1 (monocyte chemotactic protein–induced protein 1), a novel cytokine-induced antiinflammatory protein, in this process. Basal MCPIP1 expression was lower in rat vs. human islets and beta-cells. Proinflammatory cytokines stimulated MCPIP1 expression in rat and human islets and in insulin-secreting cells. Moderate overexpression of MCPIP1 protected insulin-secreting INS1E cells against cytokine toxicity by a mechanism dependent on the presence of the PIN/DUB domain in MCPIP1. It also reduced cytokine-induced Chop and C/ebpβ expression and maintained MCL-1 expression. The shRNA-mediated suppression of MCPIP1 led to the potentiation of cytokine-mediated NFκB activation and cytokine toxicity in human EndoC-βH1 beta-cells. MCPIP1 expression was very high in infiltrated beta-cells before and after diabetes manifestation in the LEW.1AR1-iddm rat model of human T1DM. The extremely high expression of MCPIP1 in clonal beta-cells was associated with a failure of the regulatory feedback-loop mechanism, ER stress induction and high cytokine toxicity. In conclusion, our data indicate that the expression level of MCPIP1 affects the susceptibility of insulin-secreting cells to cytokines and regulates the mechanism of beta-cell death in T1DM.

MCPIP1 negatively regulate cellular antiviral innate immune responses through DUB and disruption of TRAF3-TBK1-IKKε complex

IFNβ innate immune plays an essential role in antiviral immune. Previous reports suggested that many important regulatory proteins in innate immune pathway may be modified by ubiquitin and that many de-ubiquitination (DUB) proteins may affect immunity. Monocyte chemotactic protein-inducing protein 1 (MCPIP1), one of the CCCH Zn finger-containing proteins, was reported to have DUB function, but its effect on IFNβ innate immune was not fully understood. In this study, we uncovered a novel mechanism that may explain how MCPIP1 efficiently inhibits IFNβ innate immune. It was found that MCPIP1 negatively regulates the IFNβ expression activated by RIG-I, STING, TBK1, IRF3. Furthermore, MCPIP1 inhibits the nuclear translocation of IRF3 upon stimulation with virus, which plays a key role in type I IFN expression. Additionally, MCPIP1 interacts with important modulators of IFNβ expression pathway including IPS1, TRAF3, TBK1 and IKKε. Meanwhile, the interaction between the components in TRAF3-TBK1-IKKε complex was disrupted by MCPIP1. These results collectively suggest MCPIP1 as an innate immune regulator encoded by the host and point to a new mechanism through which MCPIP1 negatively regulates IRF3 activation and type I IFNβ expression.

Substrate specificity of human MCPIP1 endoribonuclease

MCPIP1, also known as Regnase-1, is a ribonuclease crucial for regulation of stability of transcripts related to inflammatory processes. Here, we report that MCPIP1 acts as an endonuclease by degrading several stem-loop RNA structures and single-stranded RNAs. Our studies revealed cleavage sites present in the stem-loops derived from the 3′ untranslated region of the interleukin-6 transcript. Furthermore, MCPIP1 induced endonuclease cleavage at the loop motif of stem-loop structures. Additionally, we observed that MCPIP1 could cleave single-stranded RNA fragments. However, RNA substrates shorter than 6 nucleotides were not further affected by MCPIP1 nucleolytic activity. In this study, we also determined the dissociation constants of full-length MCPIP1_D141N and its ribonuclease domain PIN D141N with twelve oligonucleotides substrates. The equilibrium binding constants (Kd) for MCPIP1_D141N and the RNA targets were approximately 10 nM. Interestingly, we observed that the presence of a zinc finger in the PIN domain increases the affinity of this protein fragment to 25-nucleotide-long stem-loop RNA but not to shorter ones. Furthermore, size exclusion chromatography of the MCPIP1 and PIN proteins suggested that MCPIP1 undergoes homooligomerization during interaction with RNA substrates. Our results provide insight into the mechanism of MCPIP1 substrate recognition and its affinity towards various oligonucleotides.

MCPIP1 attenuates the innate immune response to influenza A virus by suppressing RIG-I expression in lung epithelial cells

The pattern recognition receptor retinoic acid-inducible gene I (RIG-I) reportedly plays a key role in sensing influenza A virus (IAV) infection and activating type I interferon (IFN) response. MCP-1-induced protein 1 (MCPIP1) can directly degrade cytokine mRNAs, such as IL-6, IL-12, IL-1β, and IL-2, by functioning as an RNase. Here, we initially observed that MCPIP1 exhibited virus supportive functions later in the course of IAV infection in A549 cells, and negatively regulated IAV-induced RIG-I-dependent innate antiviral response. Exogenous overexpression of MCPIP1 suppressed the expression of RIG-I, whereas shRNA-mediated inhibition of endogenous MCPIP1 enhanced RIG-I expression. The results of experiments with actinomycin D and luciferase assay demonstrated that MCPIP1 reduced RIG-I expression through destabilizing its mRNA. Various mutants of functional domains of MCPIP1 further confirmed that the inhibitory effect of MCPIP1 on RIG-I expression required RNase activity but not deubiquitinase activity. Finally, the overexpression of several IAV proteins, which have the ability to inhibit the host IFN response at different levels, induced MCPIP1 expression, especially non-structural protein 1 (NS1). Conclusively, these data demonstrate the MCPIP1 contributes to attenuate IAV-induced host antiviral response by suppressing RIG-I expression.

MCPIP1 Downregulation in Clear Cell Renal Cell Carcinoma Promotes Vascularization and Metastatic Progression

Clear cell renal cell carcinoma (ccRCC) is the most common type of kidney cancer and it forms highly vascularized tumors. The monocyte endoribonuclease MCPIP1 negatively regulates inflammation by degrading mRNA encoding proinflammatory cytokines, such as IL6, IL1, and IL12. MCPIP1 is also a negative regulator of NFκB and AP1 activity and it influences a broad range of miRNA activities. Here we report that MCPIP1 protein levels are decreased during renal cancer progression. In patient-derived tumors and xenografts established in NOD-SCID or nude mice, low MCPIP1 levels correlated strongly with increased proliferation, tumor outgrowth, and vascularity. MCPIP1 activity regulated secretion of VEGF, IL8, and CXCL12 leading to chemotaxis of microvascular endothelial cells, phosphorylation of VE-cadherin, and increased vascular permeability. Mechanistic investigations showed that MCPIP1 regulated ccRCC cell motility, lung metastasis, and mesenchymal phenotype by regulating key elements in the EMT signaling axis. Overall, our results illuminate how MCPIP1 serves as a key nodal point in coordinating tumor growth, angiogenesis, and metastatic spread in ccRCC. Cancer Res; 77(18); 4905-20. ©2017 AACR.

MCPIP1 contributes to the inflammatory response of UVB-treated keratinocytes

BACKGROUND

Monocyte chemoattractant protein-1-induced protein-1 (MCPIP1), also known as regnase-1, negatively regulates many cellular processes including the cellular response to inflammatory agents, differentiation, viability, and proliferation. It possesses a PilT N-terminus (PIN) domain that is directly involved in regulating the stability of transcripts and miRNAs by recognizing stem loop structures and degrading them by endonucleolytic cleavage.

OBJECTIVE

We investigated the role of MCPIP1 in the response of human primary keratinocytes to UVB stress.

METHODS

Keratinocytes were treated with UVB, siRNA against MCPIP1, pharmacological inhibitors of signaling pathways, or subjected to control treatments. The mRNA and protein levels of MCPIP1 and MCPIP1-dependent changes gene expression were analyzed by quantitative (Q)-RT-PCRs and Western blots. Secretion of TNFα and IL-8 was determined by ELISA.

RESULTS

UVB treatment of keratinocytes induced upregulation of MCPIP1 at the mRNA level after 4-8h and at the protein level after 8-16h. MCPIP1 abundance depended on NF-κB activity. Using an siRNA strategy, we found that diminished MCPIP1 resulted in an up-regulation of transcripts coding for IL-8, TNFα, COX-2, and BCL-2, as well as an enhanced release of IL-8. Moreover, decreased phosphorylation of NF-κB and p38 signaling pathways were observed in addition to a slight up-regulation of ERK1/2 directly after UVB treatment. Twenty-four hours later, decreased phosphorylation was observed only for NF-κB and p38. Furthermore, in MCPIP1-suppressed cells, the levels of pro-apoptotic Puma, the phosphorylated form of p53 and the abundance of its target p21 as well as the activity of caspase 3 decreased, while the level of cyclin D1 increased.

CONCLUSION

MCPIP1 contributes to the UVB response of keratinocytes by altering metabolic and apoptotic processes and the release of inflammatory mediators.

MCPIP1, alias Regnase-1 binds and cleaves mRNA of C/EBPβ

CCAAT/enhancer-binding protein beta (C/EBPβ) is a transcription factor controlling a broad range of genes essential for homeostasis, including genes related to immune functions, inflammation, metabolism and growth. Monocyte chemoattractant protein-1-induced protein 1 (MCPIP1) also called as Regnase-1 is an RNase and has been shown to decrease the stability of short-lived transcripts coding for inflammation-related proteins, including IL-1β, IL-6, IL-2, IL-8, IL-12b, IER-3, c-Rel. We found previously that the half-life of the C/EBPβ transcript is regulated by MCPIP. To understand the mechanism driving down-regulation of C/EBPβ by MCPIP1, we applied an in vitro cleavage assay, followed by a luciferase-reporter assay and RNA immunoprecipitation (RIP). We demonstrated that MCPIP1 recognizes regions of the 3’UTR of C/EBPβ mRNA and promotes its decay by introducing direct endonucleolytic cleavage.