Myocardial injury modulates the innate immune system and changes myocardial sensitivity

TLR4-A Pertinent Player in Radiation-Induced Heart Disease?

The heart is one of the organs that is sensitive to developing delayed adverse effects of ionizing radiation (IR) exposure. Radiation-induced heart disease (RIHD) occurs in cancer patients and cancer survivors, as a side effect of radiation therapy of the chest, with manifestation several years post-radiotherapy. Moreover, the continued threat of nuclear bombs or terrorist attacks puts deployed military service members at risk of exposure to total or partial body irradiation. Individuals who survive acute injury from IR will experience delayed adverse effects that include fibrosis and chronic dysfunction of organ systems such as the heart within months to years after radiation exposure. Toll-like receptor 4 (TLR4) is an innate immune receptor that is implicated in several cardiovascular diseases. Studies in preclinical models have established the role of TLR4 as a driver of inflammation and associated cardiac fibrosis and dysfunction using transgenic models. This review explores the relevance of the TLR4 signaling pathway in radiation-induced inflammation and oxidative stress in acute as well as late effects on the heart tissue and the potential for the development of TLR4 inhibitors as a therapeutic target to treat or alleviate RIHD.

The E3 Ligase TRIM16 Is a Key Suppressor of Pathological Cardiac Hypertrophy

Background: Pathological cardiac hypertrophy is one of the leading causes of heart failure with highly complicated pathogeneses. The E3 ligase TRIM16 (tripartite motif-containing protein 16) has been recognized as a pivotal regulator to control cell survival, immune response, and oxidative stress. However, the role of Trim16 in cardiac hypertrophy is unknown.

METHODS

We generated cardiac-specific knockout mice and adeno-associated virus serotype 9-Trim16 mice to evaluate the function of Trim16 in pathological myocardial hypertrophy. The direct effect of TRIM16 on cardiomyocyte enlargement was examined using an adenovirus system. Furthermore, we combined RNA-sequencing and interactome analysis that was followed by multiple molecular biological methodologies to identify the direct target and corresponding molecular events contributing to TRIM16 function.

RESULTS

We found an intimate correlation of Trim16 expression with hypertrophy-related heart failure in both human and mouse. Our functional investigations and unbiased transcriptomic analyses clearly demonstrated that Trim16 deficiency markedly exacerbated cardiomyocyte enlargement in vitro and in transverse aortic constriction-induced cardiac hypertrophy mouse model, whereas Trim16 overexpression attenuated cardiac hypertrophy and remodeling. Mechanistically, Prdx1 (peroxiredoxin 1) is an essential target of Trim16 in cardiac hypertrophy. We found that Trim16 interacts with Prdx1 and inhibits its phosphorylation, leading to a robust enhancement of its downstream Nrf2 (nuclear factor-erythroid 2-related factor 2) pathway to block cardiac hypertrophy. Trim16-blocked Prdx1 phosphorylation was largely dependent on a direct interaction between Trim16 and Src and the resultant Src ubiquitinational degradation. Notably, Prdx1 knockdown largely abolished the anti-hypertrophic effects of Trim16 overexpression.

CONCLUSIONS

Our findings provide the first evidence supporting Trim16 as a novel suppressor of pathological cardiac hypertrophy and indicate that targeting the Trim16-Prdx1 axis represents a promising therapeutic strategy for hypertrophy-related heart failure.

Key Player in Cardiac Hypertrophy, Emphasizing the Role of Toll-Like Receptor 4

Toll-like receptor 4 (TLR4), a key pattern recognition receptor, initiates the innate immune response and leads to chronic and acute inflammation. In the past decades, accumulating evidence has implicated TLR4-mediated inflammatory response in regulation of myocardium hypertrophic remodeling, indicating that regulation of the TLR4 signaling pathway may be an effective strategy for managing cardiac hypertrophy's pathophysiology. Given TLR4's significance, it is imperative to review the molecular mechanisms and roles underlying TLR4 signaling in cardiac hypertrophy. Here, we comprehensively review the current knowledge of TLR4-mediated inflammatory response and its interaction ligands and co-receptors, as well as activation of various intracellular signaling. We also describe the associated roles in promoting immune cell infiltration and inflammatory mediator secretion, that ultimately cause cardiac hypertrophy. Finally, we provide examples of some of the most promising drugs and new technologies that have the potential to attenuate TLR4-mediated inflammatory response and prevent or reverse the ominous cardiac hypertrophy outcomes.

Luteolin suppresses lipopolysaccharide‑induced cardiomyocyte hypertrophy and autophagy in vitro

Luteolin (LTL) serves essential roles in a wide variety of biological processes. Lipopolysaccharide (LPS) can lead to myocardial hypertrophy and autophagy. However, the roles of LTL on LPS-induced cardiomyocyte hypertrophy and autophagy in rat cardiomyocytes have not yet been fully elucidated. In the present study, the morphology of cultured rat cardiomyocytes was observed under an inverted microscope. Cell viability was detected by MTT assay. α-Actinin and microtubule-associated protein 1 light chain 3 (LC3) expression levels were measured by immunofluorescence assay. In addition, the expression levels of atrial natriuretic peptide/brain natriuretic peptide (ANP/BNP), LC3, and autophagy- and Wnt signaling pathway-associated genes were analyzed by reverse transcription-quantitative polymerase chain reaction or western blot assays. The results indicated that LTL increased the cell viability of cardiomyocytes treated with LPS. LTL decreased the expression of cardiac hypertrophy associated markers (ANP and BNP). LTL decreased α-actinin and LC3 expression levels in LPS-treated cardiomyocytes. It was also demonstrated that LTL suppressed the mRNA and protein expression levels of LPS-mediated autophagy and Wnt signaling pathway-associated genes. In addition, it was demonstrated that silencing of β-catenin inhibited LPS-induced cardiomyocyte hypertrophy and the formation of autophagosomes. Thus, the present study suggested that LTL protected against LPS-induced cardiomyocyte hypertrophy and autophagy in rat cardiomyocytes.

Contractile deficits in engineered cardiac microtissues as a result of MYBPC3 deficiency and mechanical overload

The integration of in vitro cardiac tissue models, human induced pluripotent stem cells (hiPSCs) and genome-editing tools allows for the enhanced interrogation of physiological phenotypes and the recapitulation of disease pathologies. Here, in a cardiac tissue model consisting of filamentous 3D matrices populated with cardiomyocytes (CMs) derived from healthy wild-type hiPSCs (WT hiPSC-CMs) or from isogenic hiPSCs deficient in the sarcomere protein cardiac myosin binding protein C (MYBPC3^−/− hiPSC-CMs), we show that the WT microtissues adapted to the mechanical environment with increased contraction force commensurate to matrix stiffness, whereas the MYBPC3^−/− microtissues exhibited impaired force-development kinetics regardless of matrix stiffness and deficient contraction force only when grown on matrices with high fiber stiffness. Under mechanical overload, the MYBPC3^−/− microtissues had a higher degree of calcium transient abnormalities, and exhibited an accelerated decay of calcium dynamics as well as calcium desensitization, which accelerated when contracting against stiffer fibers. Our findings suggest that MYBPC3 deficiency and the presence of environmental stresses synergistically lead to contractile deficits in the cardiac tissues.

Periodontal bacteria DNA findings in human cardiac tissue - Is there a link of periodontitis to heart valve disease?

BACKGROUND

The aim of the study was to detect periodontal pathogens DNA in atrial and myocardial tissue, and to investigate periodontal status and their connection to cardiac tissue inflammation.

METHODS

In 30 patients, biopsy samples were taken from the atrium (A) and the ventricle myocardium (M) during aortic valve surgery. The dental examination included the dental and periodontal status (PS) and a collection of a microbiological sample. The detection of 11 periodontal pathogens DNA in oral and heart samples was carried out using PCR. The heart samples were prepared for detecting the LPS-binding protein (LBP), and for inflammation scoring on immunohistochemistry (IHC), comprising macrophages (CD68), LPS-binding protein receptor (CD14), and LBP (big42).

RESULTS

28 (93%) patients showed moderate to severe periodontitis. The periodontal pathogens in the oral samples of all patients revealed a similar distribution (3-93%). To a lesser extent and with a different distribution, these bacteria DNA were also detected in atrium and myocardium (3-27%). The LBP was detected in higher amount in atrium (0.22±0.16) versus myocardium (0.13±0.13, p=0.001). IHC showed a higher inflammation score in atrial than myocardial tissue as well as for CD14, CD68 and for LBP. Additional, periodontal findings showed a significant correlation to CD14 and CD68.

CONCLUSION

The results provide evidence of the occurrence of oral bacteria DNA at the cardiac tissue, with a different impact on atrial and myocardial tissue inflammation. Influence of periodontal findings was identified, but their relevance is not yet distinct. Therefore further clinical investigations with long term implication are warranted.

Soluble adenylyl cyclase: A novel player in cardiac hypertrophy induced by isoprenaline or pressure overload

Aims

In contrast to the membrane bound adenylyl cyclases, the soluble adenylyl cyclase (sAC) is activated by bicarbonate and divalent ions including calcium. sAC is located in the cytosol, nuclei and mitochondria of several tissues including cardiac muscle. However, its role in cardiac pathology is poorly understood. Here we investigate whether sAC is involved in hypertrophic growth using two different model systems.

Methods and results

In isolated adult rat cardiomyocytes hypertrophy was induced by 24 h β₁-adrenoceptor stimulation using isoprenaline (ISO) and a β₂-adrenoceptor antagonist (ICI118,551). To monitor hypertrophy cell size along with RNA/DNA- and protein/DNA ratios as well as the expression level of α-skeletal actin were analyzed. sAC activity was suppressed either by treatment with its specific inhibitor KH7 or by knockdown. Both pharmacological inhibition and knockdown blunted hypertrophic growth and reduced expression levels of α-skeletal actin in ISO/ICI treated rat cardiomyocytes. To analyze the underlying cellular mechanism expression levels of phosphorylated CREB, B-Raf and Erk1/2 were examined by western blot. The results suggest the involvement of B-Raf, but not of Erk or CREB in the pro-hypertrophic action of sAC. In wild type and sAC knockout mice pressure overload was induced by transverse aortic constriction. Hemodynamics, heart weight and the expression level of the atrial natriuretic peptide were analyzed. In accordance, transverse aortic constriction failed to induce hypertrophy in sAC knockout mice. Mechanistic analysis revealed a potential role of Erk1/2 in TAC-induced hypertrophy.

Conclusion

Soluble adenylyl cyclase might be a new pivotal player in the cardiac hypertrophic response either to long-term β₁-adrenoceptor stimulation or to pressure overload.

Sarcomeric lesions and remodeling proximal to intercalated disks in overload-induced cardiac hypertrophy

Pressure overload induces cardiac remodeling involving both the contractile machinery and intercalated disks (IDs). Filamin C (FlnC) and Xin actin-binding repeat-containing proteins (XIRPs) are multi-adapters localizing in IDs of higher vertebrates. Knockout of the gene encoding Xin (Xirp1) in mice leads to a mild cardiac phenotype with ID mislocalization. In order to amplify this phenotype, we performed transverse aortic constriction (TAC) on control and Xirp1-deficient mice. TAC induced similar left ventricular hypertrophy in both genotypes, suggesting that the lack of Xin does not lead to higher susceptibility to cardiac overload. However, in both genotypes, FlnC appeared in "streaming" localizations across multiple sarcomeres proximal to the IDs, suggesting a remodeling response. Furthermore, FlnC-positive areas of remodeling, reminiscent of sarcomeric lesions previously described for skeletal muscles (but so far unreported in the heart), were also observed. These adaptations reflect a similarly strong effect of the pressure induced by TAC in both genotypes. However, 2 weeks post-operation TAC-treated knockout hearts had reduced levels of connexin43 and slightly increased incidents of ventricular tachycardia compared to their wild-type (WT) counterparts. Our findings highlight the FlnC-positive sarcomeric lesions and ID-proximal streaming as general remodeling responses in cardiac overload-induced hypertrophy.

Tlr2 deficiency does not limit the development of left ventricular hypertrophy in a model of transverse aortic constriction induced pressure overload

Background

Toll-like receptors (TLRs) are involved in a variety of cardiovascular disorders, including septic cardiomyopathy, ischemia/reperfusion, heart failure, and cardiac hypertrophy. Previous research revealed that TLR4 promotes cardiac hypertrophy in vivo. Therefore, we investigated whether TLR2 is also involved in the development of cardiac hypertrophy.

Methods

Tlr2 deficient and wild type mice were subjected to transverse aortic constriction (TAC) or sham operation procedure. Left ventricular, heart and lung weights as well as hemodynamic parameters were determined after 3, 14 or 28 days. Real-time RT PCR was used to evaluate left ventricular gene expression. Protein content was determined via ELISA.

Results

TAC increased systolic left ventricular pressure, contraction and relaxations velocities as well as the heart weight in both genotypes. Tlr2 deficiency significantly enhanced cardiac hypertrophy after 14 and 28 days of TAC. Left ventricular end-diastolic pressure and heart rate increased in Tlr2^−/− TAC mice only. Fourteen days of TAC led to a significant elevation of ANP, BNP, TGFβ and TLR4 mRNA levels in Tlr2^−/− left ventricular tissue.

Conclusion

These data suggest that Tlr2 deficiency may promote the development of cardiac hypertrophy and ventricular remodeling after transverse aortic constriction.

Tlr4 Deficiency Protects against Cardiac Pressure Overload Induced Hyperinflammation

Transverse aortic constriction provokes a pro-inflammatory reaction and results in cardiac hypertrophy. Endogenous ligands contribute to cardiac hypertrophy via toll-like receptor (TLR)-4 binding. A lack of TLR4 signaling diminishes hypertrophy and inflammation. Wild type mice undergoing aortic constriction respond to a lipopolysaccharide second-hit stimulus with hyperinflammation. The objective of this study was to assess whether other second-hit challenges utilizing TLR ligands provoke a comparable inflammatory reaction, and to find out whether this response is absent in TLR4 deficient mice. Assuming that cardiac stress alters the expression of pattern recognition receptors we analyzed the effects of transverse aortic constriction and second-hit virulence factor treatment on TLR expression, as well as cytokine regulation. Wild type and Tlr4-/- mice were subjected to three days of TAC and subsequently confronted with gram-positive TLR2 ligand lipoteichoic acid (LTA, 15 mg/g bodyweight) or synthetic CpG-oligodesoxynucleotide 1668 thioate (20 nmol/kg bodyweight, 30 min after D-galactosamin desensitization) signaling via TLR9. Hemodynamic measurements and organ preservation were performed 6 h after stimulation. Indeed, the study revealed a robust enhancement of LTA induced pattern recognition receptor and cytokine mRNA expression and a LTA-dependent reduction of hemodynamic pressure in TAC wild type mice. Second-Hit treatment with CpG-ODNs led to similar results. However, second-hit effects were abolished in Tlr4-/- mice. In total, these data indicate for the first time that cardiac stress increases the inflammatory response towards both, gram-negative and gram-positive, TLR ligands as well as bacterial DNA. The decrease of the inflammatory response upon TLR2 and -9 ligand challenge in TAC Tlr4-/- mice demonstrates that a lack of TLR4 signaling does not only prevent left ventricular hypertrophy but also protects the mice from a cardiac stress induced hyperinflammatory reaction.

MCP-1-induced protein attenuates post-infarct cardiac remodeling and dysfunction through mitigating NF-κB activation and suppressing inflammation-associated microRNA expression

MCP-1-induced protein (MCPIP, also known as ZC3H12A) has recently been uncovered to act as a negative regulator of inflammation. Expression of MCPIP was elevated in the ventricular myocardium of patients with ischemic heart failure. However, the role of MCPIP in the development of post-infarct cardiac inflammation and remodeling is unknown. The objective of the present study was to investigate whether MCPIP exerts an inhibitory effect on the cardiac inflammatory response and adverse remodeling after myocardial infarction (MI). Mice with cardiomyocyte-specific expression of MCPIP and their wild-type littermates (FVB/N) were subjected to permanent ligation of left coronary artery. The levels of MCPIP were significantly increased in the ischemic myocardium and sustained for 4 weeks after MI. Acute infarct size was comparable between groups. However, constitutive overexpression of MCPIP in the murine heart resulted in improved survival rate, decreased cardiac hypertrophy, less of fibrosis and scar formation, and better cardiac performance at 28 days after MI, along with a markedly reduced monocytic cell infiltration, less cytokine expression, decreased caspase-3/7 activities and apoptotic cell death compared to the wild-type hearts. Cardiomyocyte-specific expression of MCPIP also attenuated activation of cardiac NF-κB signaling and expression of inflammation-associated microRNAs (miR-126, -146a, -155, and -199a) when compared with the post-infarct wild-type hearts. In vitro, MCPIP expression suppressed hypoxia-induced NF-κB-luciferase activity in cardiomyocytes. In conclusion, MCPIP expression in the ischemic myocardium protects against adverse cardiac remodeling and dysfunction following MI by modulation of local myocardial inflammation, possibly through mitigating NF-κB signaling and suppressing inflammation-associated microRNA expression.

Toll-like receptors: new players in myocardial ischemia/reperfusion injury

Innate immune and inflammatory responses have been implicated in myocardial ischemia/reperfusion (I/R) injury. However, the mechanisms by which innate immunity and inflammatory response are involved in myocardial I/R have not been elucidated completely. Recent studies highlight the role of Toll-like receptors (TLRs) in the induction of innate immune and inflammatory responses. Growing evidence has demonstrated that TLRs play a critical role in myocardial I/R injury. Specifically, deficiency of TLR4 protects the myocardium from ischemic injury, whereas modulation of TLR2 induces cardioprotection against ischemic insult. Importantly, cardioprotection induced by modulation of TLRs involves activation of the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway, suggesting that there is a crosstalk between TLRs and PI3K/Akt signaling pathways. In addition, TLRs also associate with other coreceptors, such as macrophage scavenger receptors in the recognition of their ligands. TLRs are also involved in the induction of angiogenesis, modulation of stem cell function, and expression of microRNA, which are currently important topic areas in myocardial I/R. Understanding how TLRs contribute to myocardial I/R injury could provide basic scientific knowledge for the development of new therapeutic approaches for the treatment and management of patients with heart attack.

The toll-like receptor 4-antagonist eritoran reduces murine cardiac hypertrophy

AIMS

Toll-like receptor 4 (TLR4) recognizes lipopolysaccharides and endogenous ligands released after organ injury. Deficiency of TLR4 attenuates the development of left ventricular hypertrophy after transverse aortic constriction (TAC) in mice. We hypothesized that application of the TLR4 antagonist eritoran may also reduce cardiac hypertrophy after TAC surgery.

METHODS AND RESULTS

A catheter was implanted into the jugular vein of C57BL/6 mice to allow repeated administration of eritoran (5 mg/kg body weight) or placebo. Three days after TAC or sham surgery, heart weights were determined and cardiac tissue underwent mRNA and protein quantification. The TAC placebo group exhibited a significant increase in left ventricular weight, left ventricular weight/tibia length, and left ventricular/body weight ratio compared with the sham and TAC eritoran groups. Natriuretic peptide mRNA was elevated significantly only in TAC placebo mice. Transverse aortic constriction surgery led to a distinct increase in interleukin (IL)-1β and IL-6 mRNA and protein expression in the placebo but not the eritoran group. In contrast, IL-10 was significantly increased in both eritoran groups independent from TAC. Matrix metalloproteinase zymographic activity was highest in TAC placebo animals.

CONCLUSION

Application of the TLR4 antagonist eritoran attenuates the development of cardiac hypertrophy possibly by a reduction in inflammatory and increase in anti-inflammatory cytokines.

Cardiomyocyte Toll-like receptor 4 is involved in heart dysfunction following septic shock or myocardial ischemia

Toll-like receptors are expressed in immune cells and cardiac muscle. We examined whether the cardiac Toll-like receptor 4 (TLR4) is involved in the acute myocardial dysfunction caused by septic shock and myocardial ischemia (MI). We used wild type mice (WT), TLR4 deficient (TLR4-ko) mice and chimeras that underwent myeloablative bone marrow transplantation to dissociate between TLR4 expression in the heart (TLR4-ko/WT) and the immunohematopoietic system (WT/TLR4-ko). Mice were injected with lipopolysaccharide (LPS) (septic shock model) or subjected to coronary artery ligation (MI model) and tested in vivo and ex vivo, for function, histopathology proinflammatory cytokine and TLR4 expression. WT mice challenged with LPS or MI displayed reduced cardiac function, increased myocardial levels of IL-1 beta and TNF-alpha and upregulation of mRNA encoding TLR4 prior to myocardial leukocyte infiltration. TLR4 deficient mice sustained significantly smaller infarctions as compared to control mice at comparable areas at risk. The cardiac function of TLR4-ko mice was not affected by LPS and demonstrated reduced suppression by MI compared to WT. Chimeras deficient in myocardial TLR4 were resistant to suppression induced by LPS and the heart function was less depressed, compared to the TLR4-ko, following MI in the acute phase (4h). In contrast, hearts of chimeras deficient in immunohematopoietic TLR4 expression were suppressed both by LPS and MI, exhibiting increased myocardial cytokine levels, similar to WT mice. We concluded that cardiac function of TLR4-ko mice and chimeric mice expressing TLR4 in the immunohematopoietic system, but not in the heart, revealed resistance to LPS and reduced cardiac depression following MI, suggesting that TLR4 expressed by the cardiomyocytes themselves plays a key role in this acute phenomenon.

Cellular cardiomyoplasty: what have we learned?

Restoring blood flow, improving perfusion, reducing clinical symptoms, and augmenting ventricular function are the goals after acute myocardial infarction. Other than cardiac transplantation, no standard clinical procedure is available to restore damaged myocardium. Since we first reported cellular cardiomyoplasty in 1989, successful outcomes have been confirmed by experimental and clinical studies, but definitive long-term efficacy requires large-scale placebo-controlled double-blind randomized trials. On meta-analysis, stem cell-treated groups had significantly improved left ventricular ejection fraction, reduced infarct scar size, and decreased left ventricular end-systolic volume. Fewer myocardial infarctions, deaths, readmissions for heart failure, and repeat revascularizations were additional benefits. Encouraging clinical findings have been reported using satellite or bone marrow stem cells, but understanding of the benefit mechanisms demands additional studies. Adult mammalian ventricular myocardium lacks adequate regeneration capability, and cellular cardiomyoplasty offers a new way to overcome this; the poor retention and engraftment rate and high apoptotic rate of the implanted stem cells limit outcomes. The ideal type and number of cells, optimal timing of cell therapy, and ideal cell delivery method depend on determining the beneficial mechanisms. Cellular cardiomyoplasty has progressed rapidly in the last decade. A critical review may help us to better plan the future direction.

Atorvastatin enhances interleukin-10 levels and improves cardiac function in rats after acute myocardial infarction

LV (left ventricular) remodelling is the basic mechanism of HF (heart failure) following MI (myocardial infarction). Although there is evidence that pro-inflammatory cytokines [including TNF-alpha (tumour necrosis factor-alpha) and IL-6 (interleukin-6)] are involved in the remodelling process, only little is known about the role of anti-inflammatory cytokines, such as IL-10. As accumulating evidence has revealed that statins possess anti-inflammatory properties, the aim of the present study was to elucidate the effect of atorvastatin on the modulation of the anti-inflammatory cytokine IL-10 and its effect on LV function in rats with HF subsequent to MI. Rats with MI, induced by permanent LAD (left anterior descending) branch coronary artery ligation, were treated for 4 weeks with atorvastatin (10 mg x kg(-1) of body weight x day(-1) via oral gavage) starting on the first day after induction of MI. Cardiac function was assessed by echocardiography and cardiac catheterization 4 weeks after MI induction. Membrane-bound and soluble fractions of TNF-alpha, IL-6 and IL-10 protein, the TNF-alpha/IL-10 ratio, serum levels of MCP-1 (monocyte chemoattractant protein-1) as well as myocardial macrophage infiltration were analysed. Treatment with atorvastatin significantly improved post-MI LV function (fractional shortening, +120%; dP/dt(max), +147%; and LV end-diastolic pressure, -27%). Furthermore atorvastatin treatment markedly decreased the levels of TNF-alpha, IL-6 and MCP-1, reduced myocardial infiltration of macrophages and significantly increased myocardial and serum levels of the anti-inflammatory cytokine IL-10. Thus the balance between pro-inflammatory and anti-inflammatory cytokines was shifted in the anti-inflammatory direction, as shown by a significantly decreased TNF-alpha/IL-10 ratio. Atorvastatin ameliorated early LV remodelling and improved LV function in rats with HF subsequent to MI. Our study suggests that the modulation of the balance between pro- and anti-inflammatory cytokines towards the anti-inflammatory cytokine IL-10 is one salutary mechanism underlying how atorvastatin influences post-MI remodelling and thus improves LV function.

Interleukin-10 improves left ventricular function in rats with heart failure subsequent to myocardial infarction

Evidence has shown that pro-inflammatory cytokines, especially TNF-alpha, are involved in the inflammatory response in the remodelling process after myocardial infarction (MI). Although IL-10, an anti-inflammatory cytokine, has been shown to antagonize some of the deleterious effects of TNF-alpha, little is known about its role in post-MI left ventricular (LV) dysfunction. The aim of the present study was to investigate whether a therapy with rhIL-10 could be beneficial in an animal model of post-MI heart failure (HF). Rats with experimental MI were treated with rhIL-10 (75 microg/kg/d sc) starting directly after MI induction, and continuing for 4 weeks. Controls were untreated MI and sham-operated rats. Cardiac function was assessed by echocardiography and cardiac catheterization 4 weeks after MI induction. Membrane-bound and soluble fractions of TNF-alpha, IL-6 and IL-10, the ratio of TNF-alpha to IL-10, serum levels of MCP-1 as well as myocardial macrophage infiltration, were analyzed. Treatment with rhIL-10 significantly improved post-MI LV function (FS +127%;, dP/dt(max) +131%; LVEDP -36%). This effect was associated with a significant decrease in pro-inflammatory cytokine and chemokine levels (TNF-alpha, IL-6, MCP-1) and furthermore resulted in a reduced myocardial infiltration of macrophages.