Dynamic alterations in the CaV1.2/CaM/CaMKII signaling pathway in the left ventricular myocardium of ischemic rat hearts

Sphingosylphosphorylcholine alleviates pressure overload-induced myocardial remodeling in mice via inhibiting CaM-JNK/p38 signaling pathway

Apoptosis plays a critical role in the development of heart failure, and sphingosylphosphorylcholine (SPC) is a bioactive sphingolipid naturally occurring in blood plasma. Some studies have shown that SPC inhibits hypoxia-induced apoptosis in myofibroblasts, the crucial non-muscle cells in the heart. Calmodulin (CaM) is a known SPC receptor. In this study we investigated the role of CaM in cardiomyocyte apoptosis in heart failure and the associated signaling pathways. Pressure overload was induced in mice by trans-aortic constriction (TAC) surgery. TAC mice were administered SPC (10 μM·kg-1·d-1) for 4 weeks post-surgery. We showed that SPC administration significantly improved survival rate and cardiac hypertrophy, and inhibited cardiac fibrosis in TAC mice. In neonatal mouse cardiomyocytes, treatment with SPC (10 μM) significantly inhibited Ang II-induced cardiomyocyte hypertrophy, fibroblast-to-myofibroblast transition and cell apoptosis accompanied by reduced Bax and phosphorylation levels of CaM, JNK and p38, as well as upregulated Bcl-2, a cardiomyocyte-protective protein. Thapsigargin (TG) could enhance CaM functions by increasing Ca2+ levels in cytoplasm. TG (3 μM) annulled the protective effect of SPC against Ang II-induced cardiomyocyte apoptosis. Furthermore, we demonstrated that SPC-mediated inhibition of cardiomyocyte apoptosis involved the regulation of p38 and JNK phosphorylation, which was downstream of CaM. These results offer new evidence for SPC regulation of cardiomyocyte apoptosis, potentially providing a new therapeutic target for cardiac remodeling following stress overload.

Bacterial toxins and heart function: heat-labile Escherichia coli enterotoxin B promotes changes in cardiac function with possible relevance for sudden cardiac death

Bacterial toxins can cause cardiomyopathy, though it is not its most common cause. Some bacterial toxins can form pores in the membrane of cardiomyocytes, while others can bind to membrane receptors. Enterotoxigenic E. coli can secrete enterotoxins, including heat-resistant (ST) or labile (LT) enterotoxins. LT is an AB5-type toxin that can bind to specific cell receptors and disrupt essential host functions, causing several common conditions, such as certain diarrhea. The pentameric B subunit of LT, without A subunit (LTB), binds specifically to certain plasma membrane ganglioside receptors, found in lipid rafts of cardiomyocytes. Isolated guinea pig hearts and cardiomyocytes were exposed to different concentrations of purified LTB. In isolated hearts, mechanical and electrical alternans and an increment of heart rate variability, with an IC50 of ~0.2 μg/ml LTB, were observed. In isolated cardiomyocytes, LTB promoted significant decreases in the amplitude and the duration of action potentials. Na+ currents were inhibited whereas L-type Ca2+ currents were augmented at their peak and their fast inactivation was promoted. Delayed rectifier K+ currents decreased. Measurements of basal Ca2+ or Ca2+ release events in cells exposed to LTB suggest that LTB impairs Ca2+ homeostasis. Impaired calcium homeostasis is linked to sudden cardiac death. The results are consistent with the recent view that the B subunit is not merely a carrier of the A subunit, having a role explaining sudden cardiac death in children (SIDS) infected with enterotoxigenic E. coli, explaining several epidemiological findings that establish a strong relationship between SIDS and ETEC E. coli.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12551-023-01100-6.

Mannose-Modified Liposome Co-Delivery of Human Papillomavirus Type 16 E7 Peptide and CpG Oligodeoxynucleotide Adjuvant Enhances Antitumor Activity Against Established Large TC-1 Grafted Tumors in Mice

Background

Previously, we demonstrated the therapeutic efficacy of a human papillomavirus (HPV) vaccine, including HPV16 E7 peptide and CpG oligodeoxynucleotides (CpG ODN), against small TC-1 grafted tumors. Here, we developed an HPV16 E7 peptide and CpG ODN vaccine delivered using liposomes modified with DC-targeting mannose, Lip E7/CpG, and determined its anti-tumor effects and influence on systemic immune responses and the tumor microenvironment (TME) in a mouse large TC-1 grafted tumor model.

Methods

L-alpha-phosphatidyl choline (SPC), cholesterol (CHOL), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (polyethylene glycol-2000)] (DSPE-PEG-2000), 1,2-dioleoyl-3-trimethylammonium-propane chloride salt (DOTAP) and Mannose-PEG-DSPE, loaded with HPV16 E7 peptide and CpG ODN, were used to construct the Lip E7/CpG vaccine. The anti-tumor effects and potential mechanism of Lip E7/CpG were assessed by assays of tumor growth inhibition, immune cells, in vivo cytotoxic T lymphocyte (CTL) responses and cytokines, chemokines, CD31, Ki67 and p53 expression in the TME. In addition, toxicity of Lip E7/CpG to major organs was evaluated.

Results

Lip E7/CpG had a diameter of 122.21±8.37 nm and remained stable at 4°C for 7 days. Co-delivery of HPV16 E7 peptide and CpG ODN by liposomes exerted potent anti-tumor effects in large (tumor volume ≥200mm³) TC-1 grafted tumor-bearing mice with inhibition rates of 80% and 78% relative to the control and Free E7/CpG groups, respectively. Vaccination significantly increased numbers of CD4+ and CD8+ T cells, and IFN-γ-producing cells in spleens and tumors and enhanced HPV-specific CTL responses, while reducing numbers of inhibitory cells including myeloid-derived suppressor cells and macrophages. Expression of cytokines and chemokines was altered and formation of tumor blood vessels was reduced in the Lip E7/CpG group, indicating possible modulation of the immunosuppressive TME to promote anti-tumor responses. Lip E7/CpG did not cause morphological changes in major organs.

Conclusion

Lip E7/CpG induced anti-tumor effects by enhancing cellular immunity and improving tumor-associated immunosuppression. Mannose-modified liposomes are the promising vaccine delivery strategy for cancer immunotherapy.

Distinct roles of calmodulin and Ca2+/calmodulin-dependent protein kinase II in isopreterenol-induced cardiac hypertrophy

Intracellular calcium is related to cardiac hypertrophy. The Ca_V1.2 channel and Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) and CaM regulate the intracellular calcium content. However, the differences in CaMKII and CaM in cardiac hypertrophy are still conflicting and are worthy of studying as drug targets. Therefore, in this study, we aim to investigate the roles and mechanism of CaM and CaMKII on Ca_V1.2 in pathological myocardial hypertrophy. The results showed that ISO stimulation caused SD rat heart and cardiomyocyte hypertrophy. In vivo, the HW/BW, LVW/BW, cross-sectional area, fibrosis ratio and ANP expression were all increased. There were no differences in Ca_V1.2 channel expression in the in vivo model or the in vitro model, but the ISO stimulation induced channel activity, and the [Ca²⁺]_i increased. The protein expression levels of CaMKII and p-CaMKII were all increased in the ISO group, but the CaM expression level decreased. AIP inhibited ANP, CaMKII and p-CaMKII expression, and ISO-induced [Ca²⁺]_i increased. AIP also reduced HDAC4, p-HDAC and MEF2C expression. However, CMZ did not play a cardiac hypertrophy reversal role in vitro. In conclusion, we considered that compared with CaM, CaMKII may be a much more important drug target in cardiac hypertrophy reversal.

Prolonged warm ischemia aggravates hepatic mitochondria damage and apoptosis in DCD liver by regulating Ca2+/CaM/CaMKII signaling pathway

This study was conducted to investigate the effect of warm ischemia duration on hepatocyte mitochondrial damage after liver transplantation, and confirm the role of CaMKIIγ in this process. Rat donation after cardiac death (DCD) liver transplantation model was established by exposing donor liver to 0 (W₀ group), 15 (W₁₅ group), and 30 (W₃₀ group) min warm ischemia. Some rats in W₁₅ group were transfected with CaMKIIγ and CaMKIIγ-shRNA lentivirus. On day 1, 3, and 7 post-transplantation, a series of experiments, including HE staining, TEM observation, ALT and AST measurement, flow cytometry analysis, qRT-PCR, and Western blotting were performed to evaluate the extent of hepatic and mitochondria damage. Within 7 days post-transplantation, prolonged ischemia led to an obvious deterioration of hepatic and mitochondria damage, presenting with a marked increase of apoptotic hepatocytes, ALT and AST levels, cells with low MMP, and AIF and Cyt C expression. CaMKIIγ overexpression caused the significant ultrastructural damage of hepatic cells, increase of cells with low MMP, enhancement of AIF and Cyt C expression, and augmented Ca²⁺/CaM/CaMKIIγ, while blocking CaMKIIγ showed an opposite result. In conclusion, ischemia duration is proportional to the extent of hepatic mitochondria damage, and CaMKIIγ plays a negative regulatory role in this process by regulating the Ca²⁺/CaM/CaMKII signaling pathway.

Effects of exercise training and TrkB blockade on cardiac function and BDNF-TrkB signaling postmyocardial infarction in rats

Exercise training is beneficial for preserving cardiac function postmyocardial infarction (post-MI), but the underlying mechanisms are not well understood. We investigated one possible mechanism, brain-derived neurotrophic factor (BDNF)-tropomyosin-related kinase B (TrkB) signaling, with the TrkB blocker ANA-12 (0.5 mg·kg^-1·day^-1). Male Wistar rats underwent sham surgery or ligation of the left descending coronary artery. The surviving MI rats were allocated as follows: sedentary MI rats treated with vehicle, exercise-trained MI rats treated with vehicle, and exercise-trained MI rats treated with ANA-12. Exercise training was done 5 days/wk for 4 wk on a motor-driven treadmill. At the end, left ventricular (LV) function was evaluated by echocardiography and a Millar catheter. Mature BDNF and downstream effectors of BDNF-TrkB signaling, Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), Akt, and AMP-activated protein kinase (AMPK), were assessed in the noninfarct area of the LV by Western blot analysis. Exercise training increased stroke volume and cardiac index and attenuated the decrease in ejection fraction (EF) and increase in LV end-diastolic pressure post-MI. ANA-12 blocked the improvement of EF and attenuated the increases in stroke volume and cardiac index but did not affect LV end-diastolic pressure. Exercise training post-MI prevented decreases in mature BDNF, phosphorylated (p-)CaMKII, p-Akt, and p-AMPKα expression. These effects were all blocked by ANA-12 except for p-AMPKα. In conclusion, the exercise-induced improvement of EF is mediated by the BDNF-TrkB axis and the downstream effectors CaMKII and Akt. BDNF-TrkB signaling appears to contribute to the improvement in systolic function by exercise training. NEW & NOTEWORTHY Exercise training improves ejection fraction and left ventricular end-diastolic pressure (LVEDP) and increases stroke volume and cardiac index in rats postmyocardial infarction (post-MI). The improvement of EF but not LVEDP is mediated by activation of the brain-derived neurotrophic factor (BDNF)-tropomyosin-related kinase B (TrkB) axis and downstream effectors Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) and Akt. This suggests that activation of BDNF-TrkB signaling and CaMKII and Akt is a promising target to attenuate progressive cardiac dysfunction post-MI.

Differential lncRNA‑mRNA co‑expression network analysis revealing the potential regulatory roles of lncRNAs in myocardial infarction

Previous studies have reported that long, non-coding RNAs (lncRNAs) are important in cardiovascular disease. However, the lncRNAs involved in myocardial infarction and their detailed mechanism have not been well characterized. In the present study, an affymetrix microarray associated with myocardial infarction was re-annotated, following which a myocardial infarction-related differential lncRNA-mRNA co-expression network (MILMN) was constructed. Subsequently, pathway enrichment analysis was used for all the mRNAs in the MILMN, and an lncRNA-pathway network was constructed. It was found that the mRNAs were predominantly involved in certain cardiovascular disease-associated pathway, for example the dilated cardiomyopathy and mitogen-activated protein kinase signaling pathway. Finally, a total of 39 key lncRNAs were identified, which regulate crucial pathways in myocardial infarction. Through pathway analysis of these 39 key lncRNAs, the novel function of an annotated lncRNAs-H19 was predicted, which may regulate apoptosis signal-regulating kinase, which is a protein that promotes pathological cardiac remodeling following myocardial infarction. The results of the present study not only provide potential non-coding RNA biomarkers, but also provide further insights into understanding the molecular mechanism of lncRNAs.