Effects of HMG-CoA reductase inhibitor on experimental autoimmune myocarditis

The Role of the Immune System in Pathobiology and Therapy of Myocarditis: A Review

The role of the immune system in myocarditis onset and progression involves a range of complex cellular and molecular pathways. Both innate and adaptive immunity contribute to myocarditis pathogenesis, regardless of its infectious or non-infectious nature and across different histological and clinical subtypes. The heterogeneity of myocarditis etiologies and molecular effectors is one of the determinants of its clinical variability, manifesting as a spectrum of disease phenotype and progression. This spectrum ranges from a fulminant presentation with spontaneous recovery to a slowly progressing, refractory heart failure with ventricular dysfunction, to arrhythmic storm and sudden cardiac death. In this review, we first examine the updated definition and classification of myocarditis at clinical, biomolecular and histopathological levels. We then discuss recent insights on the role of specific immune cell populations in myocarditis pathogenesis, with particular emphasis on established or potential therapeutic applications. Besides the well-known immunosuppressive agents, whose efficacy has been already demonstrated in human clinical trials, we discuss the immunomodulatory effects of other drugs commonly used in clinical practice for myocarditis management. The immunological complexity of myocarditis, while presenting a challenge to simplistic understanding, also represents an opportunity for the development of different therapeutic approaches with promising results.

Do Fetal Microchimeric Cells Influence Experimental Autoimmune Myocarditis?

Objective: We investigated the presence and influence of fetal microchimerism in the cardiac tissue of mated female mice submitted to experimental autoimmune myocarditis. Materials and methods: Nulliparous BALB/c females and BALB/c females mated with either BALB/c males (syngeneic mating) or C57BL/6 males (allogeneic mating) were immunized with cardiac myosin peptide MyHC-α_614-629 or kept as non-immunized controls. Immunization occurred 6-8 weeks after delivery and mice were assessed after 21 days. Results: Immunized mice of allogeneic mating had a lower production of anti-MyHC-α_614-629 antibodies compared to immunized nulliparous mice. Immunized nulliparous females had an intense mononuclear inflammatory infiltrate in cardiac tissue, associated with fibroplasia, while mated females had a lower inflammatory reaction. An increase in the frequency of microchimeric fetal cells was observed in mice submitted to allogeneic mating following immunization. Conclusion: Allogeneic cells of fetal origin could contribute to mitigating the inflammatory response in experimental myocarditis.

Rosuvastatin exerts cardioprotective effect in lipopolysaccharide-mediated injury of cardiomyocytes in an MG53-dependent manner

Background

Myocarditis is a cardiomyopathy associated with the inflammatory response. Rosuvastatin (RS) demonstrates cardioprotective effect in the clinical setting, although its cellular and molecular mechanisms in ameliorating myocarditis are largely unknown. MG53 (muscle-specific E3 ligase Mitsugumin 53), a newly identified striated muscle-specific protein, is involved in skeletal muscle membrane repair. We aimed to explore whether RS mediated the repair of cardiomyocytes in an MG53-dependent manner.

Methods

The RS-induced upregulation of MG53 was determined using RT-qPCR and western blotting. A lipopolysaccharide (LPS)-induced cell inflammatory model was constructed using rat cardiac muscle cell H9C2. Inflammatory injury was evaluated according to the alterations of cell viability, mitochondrial membrane potential, cell apoptosis, and expression of pro-inflammatory cytokines (interleukin-1β, interleukin-6, tumor necrosis factor-α, and monocyte chemoattractant protein-1). Small interfering RNAs (siRNAs) were used to silence MG53. The cardioprotective effect of RS and the inhibition of this protection by MG53 silence were evaluated in the forementioned in vitro model. The underlying mechanism was finally investigated using western blotting to detected the expressions of apoptotic markers (Bcl-2, Bax, Cleaved caspase-9, Cleaved caspase-3), cell cycle regulatory factors (Cyclin A, Cyclin E1, Cyclin D1, CDK2), and components involved in NF-κB signaling pathway (p-IκBa, Iκba, p-p65, p65).

Results

RS ameliorated LPS-induced inflammatory injury. RS upregulated the expression of MG53. MG53 was crucial for the RS-mediated repair response in vitro. Ablation of MG53 inhibited the RS-mediated protective effect. Furthermore, RS and MG53 interact in multiple signaling pathways to modulate recovery.

Conclusion

RS exerts cardioprotective effect in an MG53-dependent manner. MG53 may serve as a novel drug target for myocarditis treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02458-3.

HMG-CoA Reductase Inhibitor, Simvastatin Is Effective in Decreasing Degree of Myocarditis by Inhibiting Metalloproteinases Activation

Background: Acute myocarditis often progresses to heart failure because there is no effective, etiology-targeted therapy of this disease. Simvastatin has been shown to be cardioprotective by decreasing matrix metalloproteinases’ (MMPs) activity. The study was designed to determine whether simvastatin inhibits MMPs activity, decreases the severity of inflammation and contractile dysfunction of the heart in experimental autoimmune myocarditis (EAM). Methods: Simvastatin (3 or 30 mg/kg/day) was given to experimental rats with EAM by gastric gavage for 21 days. Then transthoracic echocardiography was performed, MMPs activity and troponin I level were determined and tissue samples were assessed under a light and transmission electron microscope. Results: Hearts treated with simvastatin did not show left ventricular enlargement. As a result of EAM, there was an enhanced activation of MMP-9, which was significantly reduced in the high-dose simvastatin group compared to the low-dose group. It was accompanied by prevention of myofilaments degradation and reduction of severity of inflammation. Conclusions: The cardioprotective effects of simvastatin in the acute phase of EAM are, at least in part, due to its ability to decrease MMP-9 activity and subsequent decline in myofilaments degradation and suppression of inflammation. These effects were achieved in doses equivalent to therapeutic doses in humans.

Peroxisome Proliferator-Activated Receptor Alpha Mediates the Beneficial Effects of Atorvastatin in Experimental Colitis

The current therapeutic options for Inflammatory Bowel Diseases (IBD) are limited. Even using common anti-inflammatory, immunosuppressive or biological therapies, many patients become unresponsive to the treatments, immunosuppressed or unable to restrain secondary infections. Statins are cholesterol-lowering drugs with non-canonical anti-inflammatory properties, whose underlying mechanisms of action still remain poorly understood. Here, we described that in vitro atorvastatin (ATO) treatment was not toxic to splenocytes, constrained cell proliferation and modulated IL-6 and IL-10 production in a dose-dependent manner. Mice exposed to dextran sulfate sodium (DSS) for colitis induction and treated with ATO shifted their immune response from Th17 towards Th2, improved the clinical and histological aspects of intestinal inflammation and reduced the number of circulating leukocytes. Both experimental and in silico analyses revealed that PPAR-α expression is reduced in experimental colitis, which was reversed by ATO treatment. While IBD patients also downregulate PPAR-α expression, the responsiveness to biological therapy relied on the restoration of PPAR-α levels. Indeed, the in vitro and in vivo effects induced by ATO treatment were abrogated in Ppara ^-/- mice or leukocytes. In conclusion, the beneficial effects of ATO in colitis are dependent on PPAR-α, which could also be a potential predictive biomarker of therapy responsiveness in IBD.

Rosuvastatin Reduces L-Type Ca2+ Current and Alters Contractile Function in Cardiac Myocytes via Modulation of β-Adrenergic Receptor Signaling

Rosuvastatin is one of the most used statins to lower plasma cholesterol levels. Although previous studies have reported remarkable cardiovascular effects of rosuvastatin (RSV), the mechanisms of these effects are largely unknown. In this study, we investigated the acute effects of RSV on L-type Ca2+ currents and contractile function of ventricular myocytes under basal conditions and during β-adrenergic stimulation. The effects of RSV were investigated in freshly isolated adult rat ventricular myocytes. L-type Ca+2 currents and myocyte contractility were recorded using patch-clamp amplifier and sarcomere length detection system. All experimental recordings were performed at 36 ± 1 °C. L-type Ca+2 currents were significantly reduced with the administration of 1 μM RSV (~ 24%) and this reduction in Ca2+ currents was observed at almost all potential ranges applied. Suppression of L-type Ca2+ current by RSV was prevented by adenylyl cyclase (AC) and protein kinase A (PKA) inhibitors SQ 22536 and KT5720, respectively. However, inhibition of Rho-associated kinases (ROCKs) by Y-27632 or nitric oxide synthase (NOS) by L-NAME failed to circumvent the inhibitory effect of RSV. Finally, we examined the effect of RSV during β-adrenergic receptor stimulation by isoproterenol and observed that RSV significantly suppresses the β-adrenergic responses in both L-type Ca2+ currents and contraction parameters. In conclusion, RSV modulates the β-adrenergic signaling cascade and thereby mimics the impact of β-adrenergic receptor blockers in adult ventricular myocytes through modulation of the AC-cAMP-PKA pathway.

Effects of statins on myocarditis: A review of underlying molecular mechanisms

Myocarditis refers to the clinical and histological characteristics of a diverse range of inflammatory cellular pathophysiological conditions which result in cardiac dysfunction. Myocarditis is a major cause of mortality in individuals less than 40 years of age and accounts for approximately 20% of cardiovascular disease (CVD) events. Myocarditis contributes to dilated cardiomyopathy in 30% of patients and can progress to cardiac arrest, which has a poor prognosis of <40% survival over 10 years. Myocarditis has also been documented after infection with SARS-CoV-2. The most commonly used lipid-lowering therapies, HMG-CoA reductase inhibitors (statins), decrease CVD-related morbidity and mortality. In addition to their lipid-lowering effects, increasing evidence supports the existence of several additional beneficial, 'pleiotropic' effects of statins. Recently, several studies have indicated that statins may attenuate myocarditis. Statins modify the lipid oxidation, inflammation, immunomodulation, and endothelial activity of the pathophysiology and have been recommended as adjuvant treatment. In this review, we focus on the mechanisms of action of statins and their effects on myocarditis, SARS-CoV-2 and CVD.

Cardiac apoptosis caused by elevated cholesterol level in experimental autoimmune myocarditis

It has been reported that cholesterol-lowing agents can ameliorate severity of myocarditis. However, the beneficial effect of the agents has been claimed to be independent of cholesterol reduction as there is no significant change in the plasma cholesterol level in myocarditis. In the present study, using experimental autoimmune myocarditis (EAM) rats as an animal model, we demonstrated that EAM induced elevation of cholesterol level and impaired cholesterol efflux capacity in the cardiac tissue. Moreover, serum high-density lipoprotein (HDL) content was reduced and HDL function associated protein Paraoxonase 1 (PON1) activity was decreased. Besides, the major structural protein within HDL, Apolipoprotein A1 (ApoA1) expression in the cardiac tissues was significantly reduced while the level of serum ApoA1 was not significantly altered. Importantly, cholesterol depleting agent methyl-β-cyclodextrin (MβCD) alleviated the development of EAM, as monitored by decreased ratio of heart weight to body weight (HW/BW), decreased infiltration of inflammatory cells and collagen deposition, improved cardiac function, reduced expression of apoptosis-related protein Bax, Fas, FasL and caspase-3 and increased level of anti-apoptotic protein Bcl-2. These results suggest that reduction of cholesterol level in cardiac tissue could suppress EAM-induced cardiac apoptosis through both intrinsic and extrinsic apoptotic pathways.

Anti-inflammatory Action of Statins in Cardiovascular Disease: the Role of Inflammasome and Toll-Like Receptor Pathways

Atherosclerosis is one type of cardiovascular disease (CVD) in which activation of the NLRP3 inflammasome and toll-like receptor (TLR) pathways is implicated. One of the most effective treatments for atherosclerosis is the use of statin medications. Recent studies have indicated that statins, in addition to their lipid-lowering effects, exert inhibitory and/or stimulatory effects on the NLRP3 inflammasome and TLRs. Some of the statins lead to activation of the inflammasome and subsequently cause secretion of IL-1β and IL-18. Thus, these actions may further aggravate the disease. On the other hand, some statins cause inhibition of the inflammasome or TLRs and along with lipid-lowering, help to improve the disease by reducing inflammation. In this article, we discuss these contradictory studies and the mechanisms of action of statins on the NLRP3 inflammasome and TLR pathways. The dose-dependent effects of statins on the NLRP3 complex are related to their chemistry, pharmacokinetic properties, and danger signals. Lipophilic statins have more pleiotropic effects on the NLRP3 complex in comparison to hydrophilic statins. Statins can suppress TLR4/MyD88/NF-ĸB signaling and cause an immune response shift to an anti-inflammatory response. Furthermore, statins inhibit the NF-ĸB pathway by decreasing the expression of TLRs 2 and 4. Statins are cost-effective drugs, which should have a continued future in the treatment of atherosclerosis due to both their immune-modulating and lipid-lowering effects.

Biocatalyzed Synthesis of Statins: A Sustainable Strategy for the Preparation of Valuable Drugs

Statins, inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, are the largest selling class of drugs prescribed for the pharmacological treatment of hypercholesterolemia and dyslipidaemia. Statins also possess other therapeutic effects, called pleiotropic, because the blockade of the conversion of HMG-CoA to (R)-mevalonate produces a concomitant inhibition of the biosynthesis of numerous isoprenoid metabolites (e.g., geranylgeranyl pyrophosphate (GGPP) or farnesyl pyrophosphate (FPP)). Thus, the prenylation of several cell signalling proteins (small GTPase family members: Ras, Rac, and Rho) is hampered, so that these molecular switches, controlling multiple pathways and cell functions (maintenance of cell shape, motility, factor secretion, differentiation, and proliferation) are regulated, leading to beneficial effects in cardiovascular health, regulation of the immune system, anti-inflammatory and immunosuppressive properties, prevention and treatment of sepsis, treatment of autoimmune diseases, osteoporosis, kidney and neurological disorders, or even in cancer therapy. Thus, there is a growing interest in developing more sustainable protocols for preparation of statins, and the introduction of biocatalyzed steps into the synthetic pathways is highly advantageous—synthetic routes are conducted under mild reaction conditions, at ambient temperature, and can use water as a reaction medium in many cases. Furthermore, their high selectivity avoids the need for functional group activation and protection/deprotection steps usually required in traditional organic synthesis. Therefore, biocatalysis provides shorter processes, produces less waste, and reduces manufacturing costs and environmental impact. In this review, we will comment on the pleiotropic effects of statins and will illustrate some biotransformations nowadays implemented for statin synthesis.

Simvastatin Inhibits Endotoxin-Induced Apoptosis in Liver and Spleen Through Up-Regulation of Survivin/NF-κB/p65 Expression

Endotoxemia is associated by dysregulated apoptosis of immune and non-immune cells. We investigated whether simvastatin has anti-apoptotic effects, and induces hepatocytes and lymphocytes survival signaling in endotoxin-induced liver and spleen injuries. Wistar rats were divided into the groups pretreated with simvastatin (20 or 40 mg/kg, orally) prior to a non-lethal dose of lipopolysaccharide (LPS), the LPS group, and the control. The severity of tissue inflammatory injuries was expressed as hepatic damage scores (HDS) and spleen damage scores (SDS), respectively. The apoptotic cell was detected by TUNEL (Terminal deoxynucleotidyl transferase dUTP Nick End Labeling) and immunohistochemical staining (expression of cleaved caspase-3, and anti-apoptotic Bcl-xL, survivin and NF-κB/p65). Simvastatin dose-dependently abolished HDS and SDS induced by LPS (p < 0.01), respectively. Simvastatin 40 mg/kg significantly decreased apoptotic index and caspase-3 cleavage in hepatocytes and lymphocytes (p < 0.01 vs. LPS group, respectively), while Bcl-XL markedly increased accordingly with simvastatin doses. In the simvastatin, groups were determined markedly increased cytoplasmic expression of survivin associated with nuclear positivity of NF-κB, in both hepatocytes and lymphocytes (p < 0.01 vs. LPS group). Cell-protective effects of simvastatin against LPS seemed to be mediated by up-regulation of survivin, which leads to reduced caspase-3 activation and inhibition of hepatocytes and lymphocytes apoptosis.

Carvedilol alleviates diabetic cardiomyopathy in diabetic rats

Diabetic cardiomyopathy (DCM) is characterized by structural and functional changes in the myocardium. Several studies have revealed that myocardial apoptosis and fibrosis occur during DCM. Studies have also indicated that oxidative stress may be a major factor associated with the development of DCM. Protein kinase C (PKC)β₂ has been demonstrated to be activated in diabetic rats, and overexpression of PKCβ₂ in the myocardium may result in cardiac hypertrophy and fibrosis. The P66^shc adaptor protein, which is mediated by PKCβ, serves an important role in apoptosis during oxidative stress. The aim of the present study was to investigate whether the PKCβ₂/P66^shc oxidative stress pathway is associated with DCM, and to investigate the role and mechanisms of carvedilol in preserving cardiac function. Experimental diabetic rat models were induced by streptozotocin treatment accompanied by high energy intake. Carvedilol was orally administrated at a dose of 1 or 10 mg/kg/day. Cardiac function was evaluated by serum N-terminal pro-B-type natriuretic peptide level and cardiac ultrasound. Myocardial inflammation, oxidative stress, apoptosis and fibrosis were assessed by histopathological and echocardiographic analyses and tests for oxidative markers. Associated proteins and factors were examined by immunohistochemical and western blot analyses. Rats in the diabetes mellitus group exhibited significantly decreased systolic cardiac function along with elevated expression levels of phosphorylated (p)-PKCβ₂, phos-P66^shc, caspase-3, malondialdehyde, collagen type I, tumor necrosis factor-α and interleukin-1β, which were accompanied by disorder in metabolic processes. Treatment with carvedilol reversed these changes. Thus, the present results suggest that the PKCβ₂/P66^shc signaling pathway may be associated with diabetic cardiomyopathy; furthermore, carvedilol, as a novel β-receptor blocker, may protect the myocardium from injury by suppressing the myocardial inflammatory response, fibrosis, P66^shc-mediated oxidative stress and subsequent apoptosis in myocardial tissue. Consequently, carvedilol may have potential as a therapy for the treatment of DCM.

Simvastatin Protects Cardiomyocytes Against Endotoxin-induced Apoptosis and Up-regulates Survivin/NF-κB/p65 Expression

This study is aimed to investigate whether simvastatin induces cardiomyocytes survival signaling in endotoxin (lipopolysaccharide, LSP)-induced myocardial injury, and if so, further to determine a role of survivin in simvastatin-anti-apoptotic effect. Wistar rats were pretreated with simvastatin (10–40 mg/kg po) before a single non-lethal dose of LPS. In myocardial tissue, LPS induced structural disorganization of myofibrils with significant inflammatory infiltrate (cardiac damage score, CDS = 3.87 ± 0.51, p < 0.05), whereas simvastatin dose-dependently abolished structural changes induced by LPS (p < 0.01). Simvastatin in 20 mg/kg and 40 mg/kg pretreatment, dose dependently, attenuated myocardial apoptosis determined as apoptotic index (28.8 ± 4.5% and 18.9 ± 3.5, p < 0.05), decreased cleaved caspase-3 expression (32.1 ± 5.8%, p < 0.01), along with significant Bcl-xL expression in the simvastatin groups (p < 0.01). Interestingly, in the simvastatin groups were determined significantly increased expression of survivin (p < 0.01), but in negative correlation with cleaved caspase-3 and apoptotic indices (p < 0.01). Simvastatin has a cardioprotective effects against LPS induced apoptosis. The effect may be mediated by up-regulation of survivin via activation of NF-κB, which leads to reduced activation of caspase-3 and consequent apoptosis of cardiomyocytes in experimental sepsis.

The Effects of Carvedilol on Cardiac Function and the AKT/XIAP Signaling Pathway in Diabetic Cardiomyopathy Rats

OBJECTIVES

Diabetic cardiomyopathy (DCM) is characterized by cardiac dysfunction, myocardial inflammation, interstitial fibrosis and cardiomyocytes apoptosis. The present study aimed to investigate the effects of carvedilol on cardiac function and the AKT/XIAP signaling pathway in DCM rats.

METHODS

Male Wistar rats were randomly divided into 3 groups: the control group, diabetic mellitus (DM) group and DM with carvedilol treatment group. DM rats were induced by streptozotocin accompanied by high energy intake. Carvedilol was orally administered at a dose of 10 mg/kg/day. After 16 weeks, the interrelated blood data were detected by biochemical analysis. Cardiac function was evaluated by echocardiography and the serum NT-proBNP level. The changes of myocardium ultrastructural and fibrosis were determined by electron microscopy and Masson's staining. Apoptotic cells were examined by TUNEL staining and interrelated proteins were measured by immunohistochemical and Western blots.

RESULTS

Rats in the DM group showed significant serum elevation of glucose, cholesterol, triglyceride, NT-proBNP, IL-1β and TNF-α, along with decreased cardiac function. Moreover, in the DM group, the levels of myocardial apoptosis and fibrosis were all increased accompanied by upregulation of caspase-3 and downregulation of phos-AKT and phos-XIAP, whereas carvedilol treatment prevented or reversed all the changes without influencing plasma levels of glucose, cholesterol and triglyceride.

CONCLUSIONS

The AKT/XIAP signaling pathway may be involved in DCM. Carvedilol can improve cardiac function, possibly not only by upregulating the AKT/XIAP antiapoptotic signaling pathway and subsequently attenuating myocardial fibrosis, but also through suppressing the myocardial inflammation response.

Hypersensitivity reactions to corticosteroids

Hypersensitivity reactions to corticosteroids (CS) are rare in the general population, but they are not uncommon in high-risk groups such as patients who receive repeated doses of CS. Hypersensitivity reactions to steroids are broadly divided into two categories: immediate reactions, typically occurring within 1 h of drug administration, and non-immediate reactions, which manifest more than an hour after drug administration. The latter group is more common. We reviewed the literature using the search terms "hypersensitivity to steroids, adverse effects of steroids, steroid allergy, allergic contact dermatitis, corticosteroid side effects, and type I hypersensitivity" to identify studies or clinical reports of steroid hypersensitivity. We discuss the prevalence, mechanism, presentation, evaluation, and therapeutic options in corticosteroid hypersensitivity reactions. There is a paucity of literature on corticosteroid allergy, with most reports being case reports. Most reports involve non-systemic application of corticosteroids. Steroid hypersensitivity has been associated with type I IgE-mediated allergy including anaphylaxis. The overall prevalence of type I steroid hypersensitivity is estimated to be 0.3-0.5%. Allergic contact dermatitis (ACD) is the most commonly reported non-immediate hypersensitivity reaction and usually follows topical CS application. Atopic dermatitis and stasis dermatitis of the lower extremities are risk factors for the development of ACD from topical CS. Patients can also develop hypersensitivity reactions to nasal, inhaled, oral, and parenteral CS. A close and detailed evaluation is required for the clinician to confirm the presence of a true hypersensitivity reaction to the suspected drug and choose the safest alternative. Choosing an alternative CS is not only paramount to the patient's safety but also ameliorates the worry of developing an allergic, and potentially fatal, steroid hypersensitivity reaction. This evaluation becomes especially important in high-risk groups where steroids are a life-saving treatment. The assessment should be done when the patient's underlying condition is in a quiescent state.

Anti-α4 Integrin Antibody Blocks Monocyte/Macrophage Traffic to the Heart and Decreases Cardiac Pathology in a SIV Infection Model of AIDS

Background

Cardiovascular disease (CVD), myocarditis and fibrosis are comorbidities of HIV⁺ individuals on durable antiretroviral therapy (ART). Although mechanisms for these vary, monocytes/macrophages are increasingly demonstrated to be key players.

Methods and Results

We directly blocked monocyte/macrophage traffic to the heart in an SIV model of AIDS using an anti-alpha-4 integrin antibody (natalizumab). Nineteen Rhesus macaques were SIVmac251 infected and CD8-lymphocyte depleted for the development of rapid AIDS. Ten animals received natalizumab once a week, for 3 weeks, and were sacrificed 1 week later. Six animals began treatment at the time of infection (early) and the remaining 4 began treatment 28 days post-infection (late), a time point we have previously established when significant cardiac inflammation occurs. Nine animals were untreated controls; of these, 3 were sacrificed early and 6 were sacrificed late. At necropsy, we found decreased SIV-associated cardiac pathology in late natalizumab-treated animals, compared to untreated controls. Early and late treatment resulted in significant reductions in numbers of CD163⁺ and CD68⁺ macrophages in cardiac tissues, compared to untreated controls, and a trend in decreasing numbers of newly recruited MAC387⁺ and BrdU⁺ (recruited) monocytes/macrophages. In late treated animals, decreased macrophage numbers in cardiac tissues correlated with decreased fibrosis. Early and late treatment resulted in decreased cardiomyocyte damage.

Conclusions

These data demonstrate a role for macrophages in the development of cardiac inflammation and fibrosis, and suggest that blocking monocyte/macrophage traffic to the heart can alleviate HIV- and SIV-associated myocarditis and fibrosis. They underscore the importance of targeting macrophage activation and traffic as an adjunctive therapy in HIV infection.

A DPP-4 inhibitor suppresses fibrosis and inflammation on experimental autoimmune myocarditis in mice

Myocarditis is a critical inflammatory disorder which causes life-threatening conditions. No specific or effective treatment has been established. DPP-4 inhibitors have salutary effects not only on type 2 diabetes but also on certain cardiovascular diseases. However, the role of a DPP-4 inhibitor on myocarditis has not been investigated. To clarify the effects of a DPP-4 inhibitor on myocarditis, we used an experimental autoimmune myocarditis (EAM) model in Balb/c mice. EAM mice were assigned to the following groups: EAM mice group treated with a DPP-4 inhibitor (linagliptin) (n = 19) and those untreated (n = 22). Pathological analysis revealed that the myocardial fibrosis area ratio in the treated group was significantly lower than in the untreated group. RT-PCR analysis demonstrated that the levels of mRNA expression of IL-2, TNF-α, IL-1β and IL-6 were significantly lower in the treated group than in the untreated group. Lymphocyte proliferation assay showed that treatment with the DPP-4 inhibitor had no effect on antigen-induced spleen cell proliferation. Administration of the DPP-4 inhibitor remarkably suppressed cardiac fibrosis and reduced inflammatory cytokine gene expression in EAM mice. Thus, the agents present in DPP-4 inhibitors may be useful to treat and/or prevent clinical myocarditis.

Rosuvastatin alleviates diabetic cardiomyopathy by inhibiting NLRP3 inflammasome and MAPK pathways in a type 2 diabetes rat model

PURPOSE

Nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome is important in inflammation of several diabetic complications. However, the potential role of NLRP3 inflammasome in the inflammatory process of diabetic cardiomyopathy (DCM) remains unclear. Although rosuvastatin (RSV) has an anti-inflammatory effect on some cardiovascular diseases, its influence on DCM is incompletely understood. We aimed to explore the effect on and underlying mechanism of RSV in DCM, and whether NLRP3 is a target for RSV.

METHODS

Type 2 diabetes was induced in rat. The characteristics of type 2 DCM were evaluated by metabolic tests, echocardiography and histopathology. The expression of factors was determined by real-time RT-PCR and western blot. Eight-week RSV treatment and NLRP3 gene silencing were used to investigate the effect and underlying target of RSV in DCM.

RESULTS

Compared with controls, diabetic rats showed severe metabolic disorder, cardiac dysfunction, fibrosis, disorganized ultrastructure, and excessive activation of thioredoxin interacting/inhibiting protein (TXNIP, p < 0.05), NLRP3 inflammasome (NLRP3, p < 0.01; apoptosis-associated speck-like protein containing a caspase recruitment domain [ASC], p < 0.05; caspase-1, p < 0.01), interleukin-1β (p < 0.01) and mitogen-activated protein kinases (MAPKs, all p < 0.01). Compared with diabetes alone, RSV ameliorated the overexpression of NLRP3 inflammasome (NLRP3, p < 0.05; ASC, p < 0.05; pro-caspase-1 p < 0.05, caspase-1 p20, p < 0.01) and MAPKs (all p < 0.05), which paralleled the cardiac protection of RSV. Silencing NLRP3 ameliorated cardiac remodeling and dysfunction. The beneficial effects of RSV in vehicle-treated rats were all abrogated in NLRP3-silenced rats.

CONCLUSIONS

The beneficial effect of RSV on DCM depended on inhibited NLRP3 inflammasome, and correlated with suppression of the MAPKs.

NLRP3 gene silencing ameliorates diabetic cardiomyopathy in a type 2 diabetes rat model

BACKGROUND

Nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome is associated with metabolic disorder and cell death, which are important triggers in diabetic cardiomyopathy (DCM). We aimed to explore whether NLRP3 inflammasome activation contributes to DCM and the mechanism involved.

METHODS

Type 2 diabetic rat model was induced by high fat diet and low dose streptozotocin. The characteristics of type 2 DCM were evaluated by metabolic tests, echocardiography and histopathology. Gene silencing therapy was used to investigate the role of NLRP3 in the pathogenesis of DCM. High glucose treated H9c2 cardiomyocytes were used to determine the mechanism by which NLRP3 modulated the DCM. The cell death in vitro was detected by TUNEL and EthD-III staining. TXNIP-siRNA and pharmacological inhibitors of ROS and NF-kB were used to explore the mechanism of NLRP3 inflammasome activation.

RESULTS

Diabetic rats showed severe metabolic disorder, cardiac inflammation, cell death, disorganized ultrastructure, fibrosis and excessive activation of NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), pro-caspase-1, activated caspase-1 and mature interleukin-1β (IL-1β). Evidence for pyroptosis was found in vivo, and the caspase-1 dependent pyroptosis was found in vitro. Silencing of NLRP3 in vivo did not attenuate systemic metabolic disturbances. However, NLRP3 gene silencing therapy ameliorated cardiac inflammation, pyroptosis, fibrosis and cardiac function. Silencing of NLRP3 in H9c2 cardiomyocytes suppressed pyroptosis under high glucose. ROS inhibition markedly decreased nuclear factor-kB (NF-kB) phosphorylation, thioredoxin interacting/inhibiting protein (TXNIP), NLRP3 inflammasome, and mature IL-1β in high glucose treated H9c2 cells. Inhibition of NF-kB reduced the activation of NLRP3 inflammasome. TXNIP-siRNA decreased the activation of caspase-1 and IL-1β.

CONCLUSION

NLRP3 inflammasome contributed to the development of DCM. NF-κB and TXNIP mediated the ROS-induced caspase-1 and IL-1β activation, which are the effectors of NLRP3 inflammasome. NLRP3 gene silencing may exert a protective effect on DCM.