Nitrosylation of cardiac CaMKII at Cys290 mediates mechanical afterload-induced increases in Ca2+ transient and Ca2+ sparks

Molecular and cellular neurocardiology in heart disease

This paper updates and builds on a previous White Paper in this journal that some of us contributed to concerning the molecular and cellular basis of cardiac neurobiology of heart disease. Here we focus on recent findings that underpin cardiac autonomic development, novel intracellular pathways and neuroplasticity. Throughout we highlight unanswered questions and areas of controversy. Whilst some neurochemical pathways are already demonstrating prognostic viability in patients with heart failure, we also discuss the opportunity to better understand sympathetic impairment by using patient specific stem cells that provides pathophysiological contextualization to study 'disease in a dish'. Novel imaging techniques and spatial transcriptomics are also facilitating a road map for target discovery of molecular pathways that may form a therapeutic opportunity to treat cardiac dysautonomia.

Mechanical gated ion channel Piezo1: Function, and role in macrophage inflammatory response

Macrophages are present in many mechanically active tissues and are often subjected to varying degrees of mechanical stimulation. Macrophages play a crucial role in resisting pathogen invasion and maintaining tissue homeostasis. Piezo-type mechanosensitive channel component 1 (Piezo1) is the main cation channel involved in the rapid response to mechanical stimuli in mammals. This channel plays a crucial role in controlling blood pressure and motor performance and regulates urinary osmotic pressure and epithelial cell proliferation and division. In recent years, numerous studies have shown that in macrophages, Piezo1 not only plays a role in regulating the aforementioned physiological processes but also participates in multiple pathological processes such as inflammation and cancer. In this review, we summarize the research progress on Piezo1-mediated regulation of macrophage-mediated inflammatory responses through downstream signalling pathways and the aerobic glycolysis pathway.

Nitric Oxide Modulates Ca2+ Leak and Arrhythmias via S-Nitrosylation of CaMKII

BACKGROUND

Nitric oxide (NO) has been identified as a signaling molecule generated during β-adrenergic receptor stimulation in the heart. Furthermore, a role for NO in triggering spontaneous Ca2+ release via S-nitrosylation of CaMKIIδ (Ca2+/calmodulin kinase II delta) is emerging. NO donors are routinely used clinically for their cardioprotective effects on the heart, but it is unknown how NO donors modulate the proarrhythmic CaMKII to alter cardiac arrhythmia incidence. We test the role of S-nitrosylation of CaMKIIδ at the Cysteine-273 inhibitory site and cysteine-290 activating site in cardiac Ca2+ handling and arrhythmogenesis before and during β-adrenergic receptor stimulation.

METHODS

We measured Ca2+-handling in isolated cardiomyocytes from C57BL/6J wild-type (WT) mice and mice lacking CaMKIIδ expression (CaMKIIδ-KO) or with deletion of the S-nitrosylation site on CaMKIIδ at cysteine-273 or cysteine-290 (CaMKIIδ-C273S and -C290A knock-in mice). Cardiomyocytes were exposed to NO donors, S-nitrosoglutathione (GSNO; 150 μM), sodium nitroprusside (200 μM), and β-adrenergic agonist isoproterenol (100 nmol/L).

RESULTS

Both WT and CaMKIIδ-KO cardiomyocytes responded to isoproterenol with a full inotropic and lusitropic Ca2+ transient response as well as increased Ca2+ spark frequency. However, the increase in Ca2+ spark frequency was significantly attenuated in CaMKIIδ-KO cardiomyocytes. The protection from isoproterenol-induced Ca2+ sparks and waves was mimicked by GSNO pretreatment in WT cardiomyocytes but lost in CaMKIIδ-C273S cardiomyocytes. When GSNO was applied after isoproterenol, this protection was not observed in WT or CaMKIIδ-C273S but was apparent in CaMKIIδ-C290A. In Langendorff-perfused isolated hearts, GSNO pretreatment limited isoproterenol-induced arrhythmias in WT but not CaMKIIδ-C273S hearts, while GSNO exposure after isoproterenol sustained or exacerbated arrhythmic events.

CONCLUSIONS

We conclude that prior S-nitrosylation of CaMKIIδ at cysteine-273 can limit subsequent β-adrenergic receptor-induced arrhythmias, but that S-nitrosylation at cysteine-290 might worsen or sustain β-adrenergic receptor-induced arrhythmias. This has important implications for the administration of NO donors in the clinical setting.

The ryanodine receptor microdomain in cardiomyocytes

The ryanodine receptor type 2 (RyR) is a key player in Ca2+ handling during excitation-contraction coupling. During each heartbeat, RyR channels are responsible for linking the action potential with the contractile machinery of the cardiomyocyte by releasing Ca2+ from the sarcoplasmic reticulum. RyR function is fine-tuned by associated signalling molecules, arrangement in clusters and subcellular localization. These parameters together define RyR function within microdomains and are subject to disease remodelling. This review describes the latest findings on RyR microdomain organization, the alterations with disease which result in increased subcellular heterogeneity and emergence of microdomains with enhanced arrhythmogenic potential, and presents novel technologies that guide future research to study and target RyR channels within specific microdomains.

Nitric Oxide modulates spontaneous Ca2+ release and ventricular arrhythmias during β-adrenergic signalling through S-nitrosylation of Calcium/Calmodulin dependent kinase II

Rationale

Nitric oxide (NO) has been identified as a signalling molecule generated during β-adrenergic receptor (AR) stimulation in the heart. Furthermore, a role for NO in triggering spontaneous Ca2+ release via S-nitrosylation of Ca2+/calmodulin kinase II delta (CaMKIIδ) is emerging. NO donors are routinely used clinically for their cardioprotective effects in the heart, but it is unknown how NO donors modulate the pro-arrhythmic CaMKII to alter cardiac arrhythmia incidence.

Objective

We test the role of S-nitrosylation of CaMKIIδ at the Cys-273 inhibitory site and Cys-290 activating site in cardiac Ca2+ handling and arrhythmogenesis before and during β-AR stimulation.

Methods and Results

We measured Ca2+-handling in isolated cardiomyocytes from C57BL/6J wild-type (WT) mice and mice lacking CaMKIIδ expression (CaMKIIδ-KO) or with deletion of the S-nitrosylation site on CaMKIIδ at Cys-273 or Cys-290 (CaMKIIδ-C273S and -C290A knock-in mice). Cardiomyocytes were exposed to NO donors, S-nitrosoglutathione (GSNO; 150 μM), sodium nitroprusside (SNP; 200 μM) and/or β-adrenergic agonist isoproterenol (ISO; 100 nM). WT and CaMKIIδ-KO cardiomyocytes treated with GSNO showed no change in Ca2+ transient or spark properties under baseline conditions (0.5 Hz stimulation frequency). Both WT and CaMKIIδ-KO cardiomyocytes responded to ISO with a full inotropic and lusitropic Ca2+ transient response as well as increased Ca2+ spark frequency. However, the increase in Ca2+ spark frequency was significantly attenuated in CaMKIIδ-KO cardiomyocytes. The protection from ISO-induced Ca2+ sparks and waves was mimicked by GSNO pre-treatment in WT cardiomyocytes, but lost in CaMKIIδ-C273S cardiomyocytes that displayed a robust increase in Ca2+ waves. This observation is consistent with CaMKIIδ-C273 S-nitrosylation being critical in limiting ISO-induced arrhythmogenic sarcoplasmic reticulum Ca2+ leak. When GSNO was applied after ISO this protection was not observed in WT or CaMKIIδ-C273S but was apparent in CaMKIIδ-C290A. In Langendorff-perfused isolated hearts, GSNO pre-treatment limited ISO-induced arrhythmias in WT but not CaMKIIδ-C273S hearts, while GSNO exposure after ISO sustained or exacerbated arrhythmic events.

Conclusions

We conclude that prior S-nitrosylation of CaMKIIδ at Cys-273 can limit subsequent β-AR induced arrhythmias, but that S-nitrosylation at Cys-290 might worsen or sustain β-AR-induced arrhythmias. This has important implications for the administration of NO donors in the clinical setting.

Orally administered sodium nitrite prevents the increased α-1 adrenergic vasoconstriction induced by hypertension and promotes the S-nitrosylation of calcium/calmodulin-dependent protein kinase II

The unsatisfactory rates of adequate blood pressure control among patients receiving antihypertensive treatment calls for new therapeutic strategies to treat hypertension. Several studies have shown that oral sodium nitrite exerts significant antihypertensive effects, but the mechanisms underlying these effects remain unclear. While these mechanisms may involve nitrite-derived S-nitrosothiols, their implication in important alterations associated with hypertension, such as aberrant α1-adrenergic vasoconstriction, has not yet been investigated. Here, we examined the effects of oral nitrite treatment on vascular responses to the α1-adrenergic agonist phenylephrine in two-kidney, one clip (2K1C) hypertensive rats and investigated the potential underlying mechanisms. Our results show that treatment with oral sodium nitrite decreases blood pressure and prevents the increased α1-adrenergic vasoconstriction in 2K1C hypertensive rats. Interestingly, we found that these effects require vascular protein S-nitrosylation, and to investigate the specific S-nitrosylated proteins we performed an unbiased nitrosoproteomic analysis of vascular smooth muscle cells (VSMCs) treated with the nitrosylating compound S-nitrosoglutathione (GSNO). This analysis revealed that GSNO markedly increases the nitrosylation of calcium/calmodulin-dependent protein kinase II γ (CaMKIIγ), a multifunctional protein that mediates the α1-adrenergic receptor signaling. This result was associated with reduced α1-adrenergic receptor-mediated CaMKIIγ activity in VSMCs. We further tested the relevance of these findings in vivo and found that treatment with oral nitrite increases CaMKIIγ S-nitrosylation and blunts the increased CaMKIIγ activity induced by phenylephrine in rat aortas. Collectively, these results are consistent with the idea that oral sodium nitrite treatment increases vascular protein S-nitrosylation, including CaMKIIγ as a target, which may ultimately prevent the increased α1-adrenergic vasoconstriction induced by hypertension. These mechanisms may help to explain the antihypertensive effects of oral nitrite and hold potential implications in the therapy of hypertension and other cardiovascular diseases associated with abnormal α1-adrenergic vasoconstriction.