Interleukin-5 alleviates cardiac remodelling via the STAT3 pathway in angiotensin II-infused mice.

Interleukin-5 (IL-5) has been reported to be involved in cardiovascular diseases, such as atherosclerosis and cardiac injury. This study aimed to investigate the effects of IL-5 on cardiac remodelling. Mice were infused with angiotensin II (Ang II), and the expression and source of cardiac IL-5 were analysed. The results showed that cardiac IL-5 expression was time- and dose-dependently decreased after Ang II infusion, and was mainly derived from cardiac macrophages. Additionally, IL-5-knockout (IL-5-/-) mice were used to observe the effects of IL-5 knockout on Ang II-induced cardiac remodelling. We found knockout of IL-5 significantly increased the expression of cardiac hypertrophy markers, elevated myocardial cell cross-sectional areas and worsened cardiac dysfunction in Ang II-infused mice. IL-5 deletion also promoted M2 macrophage differentiation and exacerbated cardiac fibrosis. Furthermore, the effects of IL-5 deletion on cardiac remodelling was detected after the STAT3 pathway was inhibited by S31-201. The effects of IL-5 on cardiac remodelling and M2 macrophage differentiation were reversed by S31-201. Finally, the effects of IL-5 on macrophage differentiation and macrophage-related cardiac hypertrophy and fibrosis were analysed in vitro. IL-5 knockout significantly increased the Ang II-induced mRNA expression of cardiac hypertrophy markers in myocardial cells that were co-cultured with macrophages, and this effect was reversed by S31-201. Similar trends in the mRNA levels of fibrosis markers were observed when cardiac fibroblasts and macrophages were co-cultured. In conclusions, IL-5 deficiency promote the differentiation of M2 macrophages by activating the STAT3 pathway, thereby exacerbating cardiac remodelling in Ang II-infused mice. IL-5 may be a potential target for the clinical prevention of cardiac remodelling.

Upregulation of CIRP by its agonist prevents the development of heart failure in myocardial infarction rats.

BACKGROUND: Downregulated expression of cold-inducible RNA binding protein (CIRP), a stress-response protein, has been demonstrated in the hearts of patients with heart failure (HF). However, whether CIRP plays a critical role in the pathogenesis of HF remains unknown. Zr17-2 is a recently identified CIRP agonist, which can enhance the expression of CIRP in hearts. Herein, we evaluated the effects of zr17-2 on the development of HF in a rat model of myocardial infarction (MI). METHODS: Male SD rats were pretreated with CIRP agonist zr17-2 or vehicle saline for 6 consecutive days, followed by MI induction. 1-week post-MI, cardiac function, and structural and molecular changes were determined by echocardiography and molecular biology methods. RESULTS: Excitingly, we found that pretreatment with zr17-2 significantly attenuated MI-induced cardiac dysfunction and dilation, coupled with reduced infarction size and cardiac remodeling. In addition, increased inflammatory response in the peri-infarcted heart including macrophage infiltration and the expression of inflammatory genes were all significantly decreased by zr17-2 pretreatment, suggesting an anti-inflammatory effect of zr17-2. Moreover, zr17-2 pretreatment also upregulated the antioxidant genes (e.g. NQO-1, Nrf2, and HO-1) level in the hearts. In isolated cultured cardiomyocytes, pretreatment with zr17-2 markedly attenuated cell injury and apoptosis induced by oxidative injury, along with elevation of Nrf2-related antioxidant genes and CIRP. However, silencing CIRP abolished zr17-2's antioxidant effects against oxidative injury, confirming that zr17-2's role is dependent on CIRP. CONCLUSION: Collectively, our study suggests CIRP plays a crucial role in the development of HF and a beneficial effect of CIRP agonist in preventing MI-induced HF, possibly via anti-inflammatory and anti-oxidant pathways.

CTRP5 Attenuates Doxorubicin-Induced Cardiotoxicity Via Inhibiting TLR4/NLRP3 Signaling.

BACKGROUND: C1q/tumor necrosis factor-related protein 5 (CTRP5) has been reported to be a crucial regulator in cardiac ischemia/reperfusion (I/R) injury. Nevertheless, the potential role of CTRP5 in doxorubicin (DOX)-induced cardiotoxicity and the potential mechanisms remain largely unclear. METHODS: We overexpressed CTRP5 in the hearts using an adeno-associated virus 9 (AAV9) system through tail vein injection. C57BL/6 mice were subjected to DOX (15 mg/kg/day, i.p.) to generate DOX-induced cardiotoxicity for 4 weeks. Subsequently, cardiac staining and molecular biological analysis were performed to analyze the morphological and biochemical effects of CTRP5 on the cardiac injury. H9c2 cells were used for validation in vitro. RESULTS: CTRP5 expression was down-regulated after DOX treatment both in vivo and in vitro. CTRP5 overexpression significantly attenuated DOX-induced cardiac injury, cardiac dysfunction, inhibited oxidative stress and inflammatory response. Mechanistically, CTRP5 overexpression markedly decreased the protein expression of toll-like receptor 4 (TLR4), NLRP3, cleaved caspase-1 and caspase-1, indicating TLR/NLRP3 signaling contributes to the cardioprotective role of CTRP5 in DOX-induced cardiotoxicity. CONCLUSIONS: Together, our findings demonstrated that CTRP5 overexpression could protect the heart from oxidative stress and inflammatory injury induced by DOX through inhibiting TLR4/NLRP3 signaling, suggesting that CTRP5 might be a potential therapeutic target in the prevention of DOX-induced cardiotoxicity.

Loss of MD1 Promotes Inflammatory and Apoptotic Atrial Remodelling in Diabetic Cardiomyopathy by Activating the TLR4/NF-κB Signalling Pathway.

INTRODUCTION: Myeloid differentiation protein 1 (MD1), a negative regulator of toll-like receptor 4 (TLR4), is widely expressed in the heart. Recent studies have shown that MD1 plays an important role in cardiac remodelling. However, the effects and potential mechanisms underlying MD1-mediated atrial remodelling in diabetic cardiomyopathy (DCM) remain unclear. Therefore, this study was designed to explore the role of MD1 in DCM-related atrial remodelling. METHODS: MD1 knockout (MD1-KO) mice and wild-type (WT) littermates were injected with streptozotocin (STZ) to establish a diabetic mouse model. These mice were then used to evaluate MD1 expression and its effects on atrial remodelling in vivo. RESULTS: MD1 expression was significantly decreased in STZ-induced diabetic mice. The loss of MD1 aggravated atrial fibrosis, inflammation, and apoptosis in DCM mice and promoted atrial remodelling. MD1-KO diabetic mice also showed higher susceptibility to atrial fibrillation (AF) and worse cardiac function. Mechanistically, the deletion of MD1 promoted the activation of the TLR4/NF-κB signalling pathway, resulting in atrial remodelling in DCM mice via increased p65 phosphorylation. CONCLUSIONS: The deletion of MD1 plays an important role in inflammatory and apoptotic atrial remodelling and increases susceptibility to AF in DCM mice, providing a new target for the preventive treatment of DCM-related atrial remodelling.

The role of Cold-Inducible RNA-binding protein in respiratory diseases.

Cold-inducible RNA-binding protein (CIRP) is a stress-response protein that is expressed in various types of cells and acts as an RNA chaperone, modifying the stability of its targeted mRNA. Intracellular CIRP could also be released into extracellular space and once released, extracellular CIRP (eCIRP) acts as a damage-associated molecular pattern (DAMP) to induce and amplify inflammation. Recent studies have found that eCIRP could promote acute lung injury (ALI) via activation of macrophages, neutrophils, pneumocytes and lung vascular endothelial cells in context of sepsis, haemorrhagic shock, intestinal ischemia/reperfusion injury and severe acute pancreatitis. In addition, CIRP is also highly expressed in the bronchial epithelial cells and its expression is upregulated in the bronchial epithelial cells of patients with chronic obstructive pulmonary diseases (COPD) and rat models with chronic bronchitis. CIRP is a key contributing factor in the cold-induced exacerbation of COPD by promoting the expression of inflammatory genes and hypersecretion of airway mucus in the bronchial epithelial cells. Besides, CIRP is also involved in regulating pulmonary fibrosis, as eCIRP could directly activate and induce an inflammatory phenotype in pulmonary fibroblast. This review summarizes the findings of CIRP investigation in respiratory diseases and the underlying molecular mechanisms.

Mitochondrial derived peptide MOTS-c prevents the development of heart failure under pressure overload conditions in mice.

MOTS-c, a mitochondrial-derived peptide (MDP), has been shown to have multiple biological activities such as antioxidation, anti-inflammation, and anti-apoptosis properties. In the present study, we aimed at evaluating the therapeutic effect of MOTS-c peptide in an animal model of heart failure. The heart failure mouse model was made by transverse aortic constriction (TAC) operations. The MOTS-c peptide was administrated subcutaneously by using an osmotic pump. At the end of the animal experiment, cardiac function was evaluated by echocardiography, and heart tissues were subjected to histological and molecular analysis. In vitro cultured H9C2 cells were used to test the effects of MOTS-c overexpression on cell death in response to H2 O2 stimulation. Our study showed that MOTS-c peptide attenuated TAC-induced cardiac dysfunction and remodelling. In addition, the MOTS-c peptide reduced the inflammatory response and upregulated the antioxidant capacity, coupled with the activation of the AMPK pathway in the heart of the TAC mouse model. In in vitro cultured cardiac cells, overexpression of MOTS-c was shown to activate the AMPK pathway and protect cell apoptosis in response to H2 O2 stimulation. Taken together, our study suggested that MOTS-c peptides may have therapeutic potential in treating HF.

Resveratrol protects against ox-LDL-induced endothelial dysfunction in atherosclerosis via depending on circ_0091822/miR-106b-5p-mediated upregulation of TLR4.

BACKGROUND: Atherosclerosis (AS) is the most common inducer of cardiovascular diseases, and resveratrol (RSV) has played a protective function in the endothelial injury of AS. This study was to explore the molecular mechanism of RSV in oxidized low-density lipoprotein (ox-LDL)-mediated endothelial dysfunction. METHODS: Circ_0091822, microRNA-106b-5p (miR-106b-5p) or toll-like receptor (TLR4) levels were examined using reverse transcription-quantitative polymerase chain reaction assay. Cell viability was detected via Cell Counting Kit-8 assay and angiogenesis was assessed by tube formation assay. Cell apoptosis was determined through flow cytometry. The protein analysis was conducted via western blot. Inflammatory cytokines were measured by enzyme-linked immunosorbent assay. The oxidative injury was evaluated using the commercial kits. The binding detection was performed via dual-luciferase reporter assay and RNA pull-down assay. RESULTS: Circ_0091822 was downregulated by RSV in ox-LDL-treated endothelial cells. RSV promoted cell viability and angiogenesis while inhibiting apoptosis, inflammation, and oxidative stress after exposure to ox-LDL. The circ_0091822 knockdown relieved the ox-LDL-induced cell damages. RSV suppressed the ox-LDL-caused endothelial dysfunction via inducing the downregulation of circ_0091822. Circ_0091822 could target miR-106b-5p, and the reversal of circ_0091822 for RSV function was achieved by sponging miR-106b-5p. Circ_0091822 absorbed miR-106b-5p to elevate the level of TLR4. RSV impeded ox-LDL-induced damages by regulating miR-106b-5p/TLR4 axis. CONCLUSION: All these findings suggested that RSV acted as an inhibitory factor in ox-LDL-induced endothelial injury via downregulating circ_0091822 to upregulate miR-106b-5p-related TLR4.

Ciliary neurotrophic factor overexpression protects the heart against pathological remodelling in angiotensin II-infused mice.

BACKGROUND: Ciliary neurotrophic factor (CNTF), which is a neural peptide, has been reported to confer cardioprotective effects. However, whether CNTF-based gene therapy could prevent cardiac remodelling remains incompletely clear. In this study, we used adeno-associated viral vector serotype 9 (AAV9)-based cardiac gene therapy to test the effects of CNTF overexpression on adverse ventricular remodelling in angiotensin II (Ang II)-infused mice. METHODS: First, AAV9-EGFP and AAV9-CNTF constructs were generated with virus concentration at 5 × 1012 vg/ml. Next, postnatal (P3-P10) mice with C57BL/6J background were administered with 5 × 1011 vg of AAV9 recombinant genome diluted in 50 µl of saline, and delivered through intraperitoneal injection. Implantation of osmotic minipumps was performed in 8-week-old male mice and human Ang II solution was administrated in the mice subcutaneously for 14 days through the pumps. Finally, we evaluated the effects of CNTF overexpression on mouse cardiac function, hypertrophy and fibrosis, as well as investigated the possible mechanisms. RESULTS: Our data showed that CNTF overexpression in mouse cardiomyocytes prevents cardiac hypertrophy and fibrosis induced by chronic Ang II stimulation. Mechanistic study found that CNTF overexpression upregulated NFE2-related factor 2 (Nrf2) antioxidant pathway, coupled with decreased ROS level in the cardiac tissues. Additionally, inflammatory cytokines were found to be reduced upon cardiac CNTF overexpression in response to chronic Ang II stimulation. CONCLUSIONS: Altogether, these results provide further evidence that CNTF can alleviate the condition of cardiac remodelling induced by chronic Ang II stimulation. Therefore, our results suggest a potential therapeutic role of CNTF in cardiac pathological remodelling.

Cold-inducible RNA-binding protein (CIRP) in inflammatory diseases: Molecular insights of its associated signalling pathways.

Cold-inducible RNA-binding protein (CIRP) was previously identified as an intracellular stress-response protein, which can respond to a variety of stress conditions by changing its expression and regulating mRNA stability through its binding site on the 3'-UTR of its targeted mRNAs. Recently, extracellular CIRP (eCIRP) was discovered to be present in various inflammatory conditions and could act as a pro-inflammatory factor. Genetic studies have demonstrated a key role for eCIRP in inflammatory conditions that led to the importance of targeting eCIRP in these diseases. Currently, the underlying mechanism of eCIRP-induced inflammation is under intensive investigation and several signalling pathways are being explored. Here, we epitomized various signalling pathways that mediate the pro-inflammatory effects of CIRP and also recapitulated all the CIRP-derived peptides that can block the interaction between CIRP and its receptors in inflammatory setting.

Role of CaMKII in free fatty acid/hyperlipidemia-induced cardiac remodeling both in vitro and in vivo.

RATIONALE: The cellular mechanisms of obesity/hyperlipidemia-induced cardiac remodeling are many and not completely elucidated. Ca2+/calmodulin-dependent protein kinase II (CaMKII), a multifunctional serine/threonine kinase, has been reported to be involved in a variety of cardiovascular diseases. However, its role in obesity/hyperlipidemia-induced cardiac remodeling is still unknown. OBJECTIVE: The objective of this study was to demonstrate the role of CaMKII in the pathogenesis of obesity/hyperlipidemia-induced cardiac remodeling both in vitro and in vivo. METHODS AND RESULTS: In cardiac-derived H9C2 cells, palmitate treatment induced cell apoptosis coupled with activation of the mitochondrial apoptotic pathway, and cell hypertrophic and fibrotic responses. All of these alterations were inhibited by pharmacological inhibition of CaMKII with either of two specific inhibitors, Myr-AIP and KN93. In addition, an increased inflammatory response coupled with activation of the MAPKs and NF-κB signaling pathway, exaggerated oxidative stress, ER stress and autophagy were also observed in palmitate-treated H9C2 cells, while pretreatment with CaMKII inhibitors decreased these pathological signals. Furthermore, we also demonstrated that TLR4 is upstream signal of CaMKII in palmitate-treated H9C2 cells. In APOE-/- mice fed a high-fat diet (HFD) for 16weeks, serum lipid profiles (FFAs, TG, TC) and blood glucose levels were significantly increased compared with mice fed a normal diet. In addition, apparent cardiac hypertrophy, fibrosis and apoptosis associated with increased inflammation, ER stress, and autophagy were also observed in the hearts of HFD-fed mice. However, all these changes were reversed by 8-weeks of KN93 peritoneal injections. KN93 also increased antioxidant defense as evidenced by increased expression of the Nrf2 system in the hearts of HFD-fed mice. CONCLUSIONS: Taken together, our results demonstrate a critical role of CaMKII in the pathogenesis of obesity/hyperlipidemia-induced cardiac remodeling. Also, TLR4 may be an upstream signal of cardiac CaMKII under hyperlipidemia conditions. These results suggest that CaMKII has the potential to be a therapeutic target in the prevention of obesity/hyperlipidemia-induced cardiac remodeling.

Regulator of G-protein signaling 5 protects cardiomyocytes against apoptosis during in vitro cardiac ischemia-reperfusion in mice by inhibiting both JNK1/2 and P38 signaling pathways.

Ischemic heart disease is one of the most common diseases in modern society. Ischemic myocardium can be salvaged by vascular recanalization therapy, but its benefit is attenuated by injury that can occur during reperfusion. And apoptotic cell death plays an important part in myocardial ischemia-reperfusion (IR) injury. Regulator of G-protein signaling 5 (RGS5), highly expressed in different cell types of the human adult heart, is a guanosine triphosphatase-activating protein to inhibit many signaling pathways such as c-Jun NH2-terminal kinase 1/2 (JNK1/2) and p38 which promote cardiac IR-induced apoptosis. However the role of RGS5 in cardiac IR-induced apoptosis remains unclear. An in vitro IR model was applied to the isolated hearts of wild type mice (WT), RGS5-transgenic mice (TG), and RGS5-knockout mice (KO). Our results revealed that compared with either WT or KO mice, TG mice showed inhibition of cardiomyocyte apoptosis as indicated by a greater increase of B cell lymphoma/lewkmia-2 (Bcl-2), and an obvious reduction in the positive expression of the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), Bcl-2 Associated X protein (Bax), and active caspase-3. Moreover, the inhibition of both JNK1/2 and p38 signaling markedly reversed IR-induced cardiomyocyte apoptosis in RGS5-KO mice. These studies show that RGS5 protects cardiomyocytes against apoptosis during IR through inhibiting both JNK1/2 and p38 signaling pathways.

Crocin alleviates neurotoxicity induced by bupivacaine in SH-SY5Y cells with inhibition of PI3K/AKT signaling.

BACKGROUND: Bupivacaine, a common local anesthetic, can cause neurotoxicity and permanent neurological disorders. Crocin has been widely reported as a potential neuroprotective agent in neural injury models. OBJECTIVE: The aim of this study was to investigate the role and regulatory mechanism of crocin underlying bupivacaine-induced neurotoxicity. METHOD: Human neuroblastoma SH-SY5Y cells were treated with bupivacaine and/or crocin for 24 h, followed by detecting cell viability using 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay. The effect of crocin or bupivacaine on SH-SY5Y cell proliferation was measured by Ki67 immunofluorescence assay. The levels of apoptosis-related proteins and the markers in the PI3K/Akt signaling pathway were examined using western blot analysis. The activities of caspase 3, catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA) and glutathione peroxidase (GSH-Px) were tested using respective commercial assay kits. Flow cytometry analysis was executed for detecting SH-SY5Y cell apoptosis. RESULT: Crocin attenuated bupivacaine-induced neurotoxicity in SH-SY5Y cells. Meanwhile, crocin inhibited SH-SY5Y cell apoptosis induced by bupivacaine via repressing the activity of caspase-3, reducing Bax expression, and elevating Bcl-2 expression. Moreover, crocin mitigated oxidative stress in SH-SY5Y cells by increasing the content of CAT, SOD, GSH-Px and reducing the content of MDA. Additionally, crocin protected against bupivacaine-induced dephosphorylation of Akt and GSK-3ß. The protective effects of crocin against bupivacaine-induced neurotoxicity in SH-SY5Y cells were counteracted by the Akt inhibitor. CONCLUSION: These results suggested that crocin may exert a neuroprotective function by promoting cell proliferation and suppressing apoptosis and oxidative stress in SH-SY5Y cells. Thus, crocin might become a promising drug for the treatment of bupivacaine-induced neurotoxicity.

AAV9-Mediated Cardiac CNTF Overexpression Exacerbated Adverse Cardiac Remodeling in Streptozotocin-Induced Type 1 Diabetic Models.

Ciliary neurotrophic factor (CNTF), which is a neural peptide, has been reported to confer cardioprotective effects. However, whether CNTF-based gene delivery could prevent cardiac remodeling in diabetes mellitus remains unknown. In this study, we used adeno-associated viral vector serotype 9 (AAV9)-based cardiac gene delivery to test the effects of CNTF overexpression on adverse ventricular remodeling in streptozotocin-induced type 1 diabetic mice models. Postnatal (P3-P10) mice were peritoneally injected with AAV9 recombinant virus carrying the CNTF gene or EGFP gene. Then, type 1 diabetic models were established by peritoneal injection of streptozotocin (200 mg/kg) in 7-week-old female mice injected with AAV9. 4 weeks later after the establishment of type 1 diabetes mellitus, mouse hearts were removed to assess the degree of cardiac remodeling. We found that CNTF overexpression in mouse cardiomyocytes exacerbated cell apoptosis and cardiac fibrosis coupled with an increased inflammatory response in the heart tissue of diabetic female mice. Taken together, our results suggested that cardiac CNTF gene delivery may not be beneficial in alleviating adverse cardiac remodeling in type 1 diabetes female mice.

The Mitochondrial-Derived Peptide MOTS-c Attenuates Oxidative Stress Injury and the Inflammatory Response of H9c2 Cells Through the Nrf2/ARE and NF-κB Pathways.

AIM: Oxidative stress and the inflammatory response contribute to the progression of cardiovascular disease. The present study aimed to investigate whether the mitochondrial-derived peptide MOTS-c could alleviate H2O2-induced oxidative stress and inflammatory status in H9c2 cells through activation of nuclear factor erythroid 2-related Factor 2 (Nrf2)/antioxidative response element (ARE) and inhibition of the NF-κB pathway. METHODS: Rat H9c2 cardiomyocytes were obtained, and 10, 20 or 50 µM MOTS-c was pretreated for 24 h before treatment with H2O2. Then, the cell was treated with 100 µM H2O2 for 1 h to induce oxidative stress. An inhibition model of sh-Nrf2 was constructed via a lentivirus expression system, and an activation model of NF-κB was achieved using phorbol 12-myristate-13-acetate (PMA). Cell viability was determined using a Cell Counting kit-8 assay. Relative measurement of relative protein and mRNA expression used western blotting and qRT-PCR, respectively. Intracellular reactive oxygen species (ROS) levels were detected using dichlorodihydrofluorescein diacetate, and malondialdehyde (MDA) and superoxide dismutase (SOD) levels were determined via commercial kits. The protein expression and distribution in the cells were visualized by immunofluorescence analysis. Enzyme-linked immunosorbent assay was used to detect the levels of inflammatory cytokines, including TNF-α, IL-6 and IL-1ß. RESULTS: We found that H2O2 treatment significantly decreased cell viability and the level of SOD, increased the levels of ROS and MDA, and upregulated the expression of inflammatory cytokines, including TNF-α, IL-6 and IL-1ß, in H9c2 cells. The expression levels of Nrf2, HO-1 and NQO-1 were significantly downregulated in the H2O2, while the phosphorylation of NF-κBp65 was promoted by H2O2. However, pretreatment with MOTS-c significantly reversed H2O2-induced damage in H9c2 cells. Moreover, both inhibition of the Nrf2/ARE pathway and activation of the NF-κB pathway significantly decreased the effects of MOTS-c, suggesting that MOTS-c might play a role in alleviating oxidative damage via the Nrf2/ARE and NF-κB pathways. CONCLUSIONS: Our investigation indicated that MOTS-c could protect against H2O2-induced inflammation and oxidative stress in H9c2 cells by inhibiting NF-κB and activating the Nrf2/ARE pathways.

The Role of Cold Inducible RNA-Binding Protein in Cardiac Physiology and Diseases.

Cold-inducible RNA-binding protein (CIRP) is an intracellular stress-response protein that can respond to various stress conditions by changing its expression and regulating mRNA stability. As an RNA-binding protein, CIRP modulates gene expression at the post-transcriptional level, including those genes involved in DNA repair, cellular redox metabolism, circadian rhythms, telomere maintenance, and cell survival. CIRP is expressed in a large variety of tissues, including testis, brain, lung, kidney, liver, stomach, bone marrow, and heart. Recent studies have observed the important role of CIRP in cardiac physiology and diseases. CIRP regulates cardiac electrophysiological properties such as the repolarization of cardiomyocytes, the susceptibility of atrial fibrillation, and the function of the sinoatrial node in response to stress. CIRP has also been suggested to protect cardiomyocytes from apoptosis under various stress conditions, including heart failure, high glucose conditions, as well as during extended heart preservation under hypothermic conditions. This review summarizes the findings of CIRP investigations in cardiac physiology and diseases and the underlying molecular mechanism.

The Akt pathway mediates the protective effects of myeloid differentiation protein 1 in pathological cardiac remodelling.

AIMS: Myeloid differentiation protein 1 (MD1) was shown to ameliorate pressure overload-induced cardiac hypertrophy and fibrosis by negatively regulating the MEK-ERK1/2 and NF-κB pathways. However, whether MD1 modulates cardiac function and whether the Akt pathway mediates the benefits of MD1 in pressure overload-induced cardiac remodelling remain unclear. METHODS AND RESULTS: Male cardiac-specific transgenic MD1 (MD1-TG) mice, MD1-knockout (KO) mice and wild-type (WT) littermates aged 8-10 weeks were subjected to sham operation and aortic banding (AB) for 4 weeks. Then, left ventricular (LV) hypertrophy, fibrosis and function of the mice were assessed. When compared with WT-AB mice, MD1-TGs showed decreased cross-sectional area (CSA) of cardiomyocytes (P < 0.001), mRNA expression of ß-myosin heavy chain (ß-MHC) (P < 0.02), ratios of heart weight/body weight and heart weight/tibia length (P < 0.04) and collagen volume fraction (P < 0.001). The LV end-diastolic diameter was reduced, and LV ejection fraction and fractional shortening were improved in MD1-TG-AB mice than in WT-AB mice (P < 0.05). In cultured H9C2 cells, adenovirus vector-mediated MD1 overexpression decreased angiotensin II-induced mRNA expression of brain natriuretic peptide (BNP) and ß-MHC and cell CSA (P < 0.002), whereas knockdown of MD1 by shRNA exhibited opposite effects (P < 0.04). Mechanistically, MD1 suppressed pathological cardiac remodelling at least partly by blocking Akt pathway. Akt inactivation by MK2206 largely offset the pro-hypertrophic effects of MD1 deficiency in angiotensin II-stimulated cardiomyocytes. CONCLUSIONS: The Akt pathway mediates the protective effects of MD1 in pressure overload-induced cardiac remodelling in mice. Targeting MD1 may provide therapeutic strategy for the treatment of pathological cardiac remodelling and heart failure.

Novel Protective Role of Myeloid Differentiation 1 in Pathological Cardiac Remodelling.

Myeloid differentiation 1 (MD-1), a secreted protein interacting with radioprotective 105 (RP105), plays an important role in Toll-like receptor 4 (TLR4) signalling pathway. Previous studies showed that MD-1 may be restricted in the immune system. In this study, we demonstrated for the first time that MD-1 was highly expressed in both human and animal hearts. We also discovered that cardiac-specific overexpression of MD-1 significantly attenuated pressure overload-induced cardiac hypertrophy, fibrosis, and dysfunction, whereas loss of MD-1 had the opposite effects. Similar results were observed for in vitro angiotensin II-induced neonatal rat cardiomyocyte hypertrophy. The antihypertrophic effects of MD-1 under hypertrophic stimuli were associated with the blockage of MEK-ERK 1/2 and NF-κB signalling. Blocking MEK-ERK 1/2 signalling with a pharmacological inhibitor (U0126) greatly attenuated the detrimental effects observed in MD-1 knockout cardiomyocytes exposed to angiotensin II stimuli. Similar results were observed by blocking NF-κB signalling with a pharmacological inhibitor (BAY11-7082). Our data indicate that MD-1 inhibits cardiac hypertrophy and suppresses cardiac dysfunction during the remodelling process, which is dependent on its modulation of the MEK-ERK 1/2 and NF-κB signalling pathways. Thus, MD-1 might be a novel target for the treatment of pathological cardiac hypertrophy.

Loss of MD1 exacerbates pressure overload-induced left ventricular structural and electrical remodelling.

Myeloid differentiation protein 1 (MD1) has been implicated in numerous pathophysiological processes, including immune regulation, obesity, insulin resistance, and inflammation. However, the role of MD1 in cardiac remodelling remains incompletely understood. We used MD1-knockout (KO) mice and their wild-type littermates to determine the functional significance of MD1 in the regulation of aortic banding (AB)-induced left ventricular (LV) structural and electrical remodelling and its underlying mechanisms. After 4 weeks of AB, MD1-KO hearts showed substantial aggravation of LV hypertrophy, fibrosis, LV dilation and dysfunction, and electrical remodelling, which resulted in overt heart failure and increased electrophysiological instability. Moreover, MD1-KO-AB cardiomyocytes showed increased diastolic sarcoplasmic reticulum (SR) Ca2+ leak, reduced Ca2+ transient amplitude and SR Ca2+ content, decreased SR Ca2+-ATPase2 expression, and increased phospholamban and Na+/Ca2+-exchanger 1 protein expression. Mechanistically, the adverse effects of MD1 deletion on LV remodelling were related to hyperactivated CaMKII signalling and increased impairment of intracellular Ca2+ homeostasis, whereas the increased electrophysiological instability was partly attributed to exaggerated prolongation of cardiac repolarisation, decreased action potential duration alternans threshold, and increased diastolic SR Ca2+ leak. Therefore, our study on MD1 could provide new therapeutic strategies for preventing/treating heart failure.