CaMKII as a pathological mediator of ER stress, oxidative stress, and mitochondrial dysfunction in a murine model of nephronophthisis

Inhibitory Effect of Luteolin on Spike S1 Glycoprotein-Induced Inflammation in THP-1 Cells via the ER Stress-Inducing Calcium/CHOP/MAPK Pathway

BACKGROUND/OBJECTIVES

The global SARS-CoV-2 outbreak has escalated into a critical public health emergency, with the spike glycoprotein S1 subunit of SARS-CoV-2 (spike-S1) linked to inflammation in lung tissue and immune cells. Luteolin, a flavone with anti-inflammatory properties, shows promise, but research on its effectiveness against long-COVID-related inflammation and spike protein-induced responses remains limited. This study aims to elucidate the underlying mechanisms of inflammation in THP-1 cells induced by the spike-S1. Additionally, it seeks to assess the potential of luteolin in mitigating inflammatory responses induced by the spike-S1 in a THP-1 macrophage model.

METHODS

The gene expression profiles of spike-S1 in THP-1 cells were analyzed by transcriptome sequencing. The inhibitory effect of luteolin on ER stress and inflammation in spike-S1-induced THP-1 cells was investigated using Western blotting, RT-PCR, and ELISA.

RESULTS

The candidate genes (CAMK2A, SIGLEC7, PPARGC1B, SEC22B, USP28, IER2, and TIRAP) were upregulated in the spike-S1-induced THP-1 group compared to the control group. Among these, calcium/calmodulin-dependent protein kinase II alpha (CAMK2A) was identified as the most promising molecule in spike-S1-induced THP-1 cells. Our results indicate that the spike S1 significantly increased the expression of ER-stress markers at both gene and protein levels. Luteolin significantly reduced ER stress by decreasing the expression of ER-stress marker genes and ER-stress marker proteins (p < 0.01). Additionally, luteolin exhibited anti-inflammatory properties upon spike S1-induction in THP-1 cells by significantly suppressing IL-6, IL-8, and IL-1β cytokine secretion in a dose-dependent manner (p < 0.05). Furthermore, our results revealed that luteolin exhibited the downregulation of the MAPK pathway, as evidenced by modulating the phosphorylation of p-ERK1/2, p-JNK and p-p38 proteins (p < 0.05).

CONCLUSIONS

The results from this study elucidate the mechanisms by which the spike S1 induces inflammation in THP-1 cells and supports the use of naturally occurring bioactive compounds, like luteolin, against inflammation-related SARS-CoV-2 infection.

Phenethyl isothiocyanate and irinotecan synergistically induce cell apoptosis in colon cancer HCT 116 cells in vitro

Irinotecan (IRI), an anticancer drug to treat colon cancer patients, causes cytotoxic effects on normal cells. Phenethyl isothiocyanate (PEITC), rich in common cruciferous plants, has anticancer activities (induction of cell apoptosis) in many human cancer cells, including colon cancer cells. However, the anticancer effects of IRI combined with PEITC on human colon cancer cells in vitro were unavailable. Herein, the aim of this study is to focus on the apoptotic effects of the combination of IRI and PEITC on human colon cancer HCT 116 cells in vitro. Propidium iodide (PI) exclusion and Annexin V/PI staining assays showed that IRI combined with PEITC decreased viable cell number and induced higher cell apoptosis than that of IRI or PEITC only in HCT 116 cells. Moreover, combined treatment induced higher levels of reactive oxygen species (ROS) and Ca2+ than that of IRI or PEITC only. Cells pre-treated with N-acetyl-l-cysteine (scavenger of ROS) and then treated with IRI, PEITC, or IRI combined with PEITC showed increased viable cell numbers than that of IRI or PEITC only. IRI combined with PEITC increased higher caspase-3, -8, and -9 activities than that of IRI or PEITC only by flow cytometer assay. IRI combined with PEITC induced higher levels of ER stress-, mitochondria-, and caspase-associated proteins than that of IRI or PEITC treatment only in HCT 116 cells. Based on these observations, PEITC potentiates IRI anticancer activity by promoting cell apoptosis in the human colon HCT 116 cells. Thus, PEITC may be a potential enhancer for IRI in humans as an anticolon cancer drug in the future.

GPRC5C regulates the composition of cilia in the olfactory system

BACKGROUND

Olfactory sensory neurons detect odourants via multiple long cilia that protrude from their dendritic endings. The G protein-coupled receptor GPRC5C was identified as part of the olfactory ciliary membrane proteome, but its function and localization is unknown.

RESULTS

High-resolution confocal and electron microscopy revealed that GPRC5C is located at the base of sensory cilia in olfactory neurons, but not in primary cilia of immature neurons or stem cells. Additionally, GPRC5C localization in sensory cilia parallels cilia formation and follows the formation of the basal body. In closer examination, GPRC5C was found in the ciliary transition zone. GPRC5C deficiency altered the structure of sensory cilia and increased ciliary layer thickness. However, primary cilia were unaffected. Olfactory sensory neurons from Gprc5c-deficient mice exhibited altered localization of olfactory signalling cascade proteins, and of ciliary phosphatidylinositol-4,5-bisphosphat. Sensory neurons also exhibited increased neuronal activity as well as altered mitochondrial morphology, and knockout mice had an improved ability to detect food pellets based on smell.

CONCLUSIONS

Our study shows that GPRC5C regulates olfactory cilia composition and length, thereby controlling odour perception.

CaMKII may regulate renal tubular epithelial cell apoptosis through YAP/NFAT2 in acute kidney injury mice

AIM

Renal tubular epithelial cell (RTEC) apoptosis is important in acute kidney injury (AKI). Calcium/calmodulin-dependent protein kinase II (CaMKII) plays an important role in cell apoptosis, but its potential role in AKI remains unknown.

METHODS

Using co-immunoprecipitation, immunofluorescence, immunohistochemistry, western blotting, flow cytometry, and cell transfection, this study aimed to verify whether CaMKII is involved in RTEC apoptosis and to explore the underlying mechanism.

RESULTS

We found that CaMKII was involved in RTEC apoptosis. In adriamycin-induced AKI mice, serum creatinine levels, cell apoptosis, CaMKII activity, and nuclear factor of activated T cells 2 (NFAT2) levels increased, whereas nuclear Yes-associated protein (YAP) expression decreased; inhibition of CaMKII activity reversed these changes. Phosphorylated CaMKII could bind to phosphorylated YAP in the cytoplasm and block it from entering the nucleus, thereby failing to inhibit NFAT2-mediated cell apoptosis. Sequestrated phosphorylated YAP in the RTEC cytoplasm was finally degraded by ubiquitination.

CONCLUSION

CaMKII may regulate RTEC apoptosis through YAP/NFAT2 in AKI mice. CaMKII may be a potent molecular target for AKI treatment.

The CaMKII Inhibitory Peptide AIP Alleviates Renal Fibrosis Through the TGF-β/Smad and RAF/ERK Pathways

Renal fibrosis is characterized by the excessive deposition of extracellular matrix that destroys and replaces the functional renal parenchyma, ultimately leading to organ failure. It is a common pathway by which chronic kidney disease can develop into end-stage renal disease, which has high global morbidity and mortality, and there are currently no good therapeutic agents available. Calcium/calmodulin-dependent protein kinase II (CaMKII) has been indicated to be closely related to the occurrence of renal fibrosis, and its specific inhibitory peptide, autocamtide-2-related inhibitory peptide (AIP), was shown to directly bind the active site of CaMKII. In this study, we examined the effect of AIP on the progression of renal fibrosis and its possible mechanism. The results showed that AIP could inhibit the expression of the fibrosis markers fibronectin, collagen I, matrix metalloproteinase 2, and α-smooth muscle actin in vivo and in vitro. Further analysis revealed that AIP could inhibit the expression of various epithelial-to-mesenchymal transformation-related markers, such as vimentin and Snail 1, in vivo and in vitro. Mechanistically, AIP could significantly inhibit the activation of CaMKII, Smad 2, Raf, and extracellular regulated protein kinases (ERK) in vitro and in vivo and reduce the expression of transforming growth factor-β (TGF-β) in vivo. These results suggested that AIP could alleviate renal fibrosis by inhibiting CaMKII and blocking activation of the TGF-β/Smad2 and RAF/ERK pathways. Our study provides a possible drug candidate and demonstrates that CaMKII is a potential pharmacological target for the treatment of renal fibrosis. SIGNIFICANCE STATEMENT: We have demonstrated that AIP significantly attenuated transforming growth factor-β-1-induced fibrogenesis and ameliorated unilateral ureteral obstruction-induced renal fibrosis through the CaMKII/TGF-β/Smad and CaMKII/RAF/ERK signaling pathways in vitro and in vivo. Our study provides a possible drug candidate and demonstrates that CaMKII can be a potential pharmacological target for the treatment of renal fibrosis.

Wall Tension and Tubular Resistance in Kidney Cystic Conditions

The progressive formation of single or multiple cysts accompanies several renal diseases. Specifically, (i) genetic forms, such as adult dominant polycystic kidney disease (ADPKD), and (ii) acquired cystic kidney disease (ACKD) are probably the most frequent forms of cystic diseases. Adult dominant polycystic kidney disease (ADPKD) is a genetic disorder characterized by multiple kidney cysts and systemic alterations. The genes responsible for the condition are known, and a large amount of literature focuses on the molecular description of the mechanism. The present manuscript shows that a multiscale approach that considers supramolecular physical phenomena captures the characteristics of both ADPKD and acquired cystic kidney disease (ACKD) from the pathogenetic and therapeutical point of view, potentially suggesting future treatments. We first review the hypothesis of cystogenesis in ADPKD and then focus on ACKD, showing that they share essential pathogenetic features, which can be explained by a localized obstruction of a tubule and/or an alteration of the tubular wall tension. The consequent tubular aneurysms (cysts) follow Laplace's law. Reviewing the public databases, we show that ADPKD genes are widely expressed in various organs, and these proteins interact with the extracellular matrix, thus potentially modifying wall tension. At the kidney and liver level, the authors suggest that altered cell polarity/secretion/proliferation produce tubular regions of high resistance to the urine/bile flow. The increased intratubular pressure upstream increases the difference between the inside (Pi) and the outside (Pe) of the tubules (∆P) and is counterbalanced by lower wall tension by a factor depending on the radius. The latter is a function of tubule length. In adult dominant polycystic kidney disease (ADPKD), a minimal reduction in the wall tension may lead to a dilatation in the tubular segments along the nephron over the years. The initial increase in the tubule radius would then facilitate the progressive expansion of the cysts. In this regard, tubular cell proliferation may be, at least partially, a consequence of the progressive cysts' expansion. This theory is discussed in view of other diseases with reduced wall tension and with cysts and the therapeutic effects of vaptans, somatostatin, SGLT2 inhibitors, and potentially other therapeutic targets.

Renal ciliopathies: promising drug targets and prospects for clinical trials

INTRODUCTION

Renal ciliopathies represent a collection of genetic disorders characterized by deficiencies in the biogenesis, maintenance, or functioning of the ciliary complex. These disorders, which encompass autosomal dominant polycystic kidney disease (ADPKD), autosomal recessive polycystic kidney disease (ARPKD), and nephronophthisis (NPHP), typically result in cystic kidney disease, renal fibrosis, and a gradual deterioration of kidney function, culminating in kidney failure.

AREAS COVERED

Here we review the advances in basic science and clinical research into renal ciliopathies which have yielded promising small compounds and drug targets, within both preclinical studies and clinical trials.

EXPERT OPINION

Tolvaptan is currently the sole approved treatment option available for ADPKD patients, while no approved treatment alternatives exist for ARPKD or NPHP patients. Clinical trials are presently underway to evaluate additional medications in ADPKD and ARPKD patients. Based on preclinical models, other potential therapeutic targets for ADPKD, ARPKD, and NPHP look promising. These include molecules targeting fluid transport, cellular metabolism, ciliary signaling and cell-cycle regulation. There is a real and urgent clinical need for translational research to bring novel treatments to clinical use for all forms of renal ciliopathies to reduce kidney disease progression and prevent kidney failure.

Wildtype heterogeneity contributes to clonal variability in genome edited cells

Genome editing tools such as CRISPR/Cas9 enable the rapid and precise manipulation of genomes. CRISPR-based genome editing has greatly simplified the study of gene function in cell lines, but its widespread use has also highlighted challenges of reproducibility. Phenotypic variability among different knockout clones of the same gene is a common problem confounding the establishment of robust genotype-phenotype correlations. Optimized genome editing protocols to enhance reproducibility include measures to reduce off-target effects. However, even if current state-of-the-art protocols are applied phenotypic variability is frequently observed. Here we identify heterogeneity of wild-type cells as an important and often neglected confounding factor in genome-editing experiments. We demonstrate that isolation of individual wild-type clones from an apparently homogenous stable cell line uncovers significant phenotypic differences between clones. Strikingly, we observe hundreds of differentially regulated transcripts (477 up- and 306 downregulated) when comparing two populations of wild-type cells. Furthermore, we show a variety of cellular and biochemical alterations in different wild-type clones in a range that is commonly interpreted as biologically relevant in genome-edited cells. Heterogeneity of wild-type cells thus contributes to variability in genome-edited cells when these are generated through isolation of clones. We show that the generation of monoclonal isogenic wild-type cells prior to genomic manipulation reduces phenotypic variability. We therefore propose to generate matched isogenic control cells prior to genome editing to increase reproducibility.

Disruption of STIM1-mediated Ca2+ sensing and energy metabolism in adult skeletal muscle compromises exercise tolerance, proteostasis, and lean mass

OBJECTIVE

Stromal interaction molecule 1 (STIM1) is a single-pass transmembrane endoplasmic/sarcoplasmic reticulum (E/SR) protein recognized for its role in a store operated Ca2+ entry (SOCE), an ancient and ubiquitous signaling pathway. Whereas STIM1 is known to be indispensable during development, its biological and metabolic functions in mature muscles remain unclear.

METHODS

Conditional and tamoxifen inducible muscle STIM1 knock-out mouse models were coupled with multi-omics tools and comprehensive physiology to understand the role of STIM1 in regulating SOCE, mitochondrial quality and bioenergetics, and whole-body energy homeostasis.

RESULTS

This study shows that STIM1 is abundant in adult skeletal muscle, upregulated by exercise, and is present at SR-mitochondria interfaces. Inducible tissue-specific deletion of STIM1 (iSTIM1 KO) in adult muscle led to diminished lean mass, reduced exercise capacity, and perturbed fuel selection in the settings of energetic stress, without affecting whole-body glucose tolerance. Proteomics and phospho-proteomics analyses of iSTIM1 KO muscles revealed molecular signatures of low-grade E/SR stress and broad activation of processes and signaling networks involved in proteostasis.

CONCLUSION

These results show that STIM1 regulates cellular and mitochondrial Ca2+ dynamics, energy metabolism and proteostasis in adult skeletal muscles. Furthermore, these findings provide insight into the pathophysiology of muscle diseases linked to disturbances in STIM1-dependent Ca2+ handling.

Emodin prevents renal ischemia-reperfusion injury via suppression of CAMKII/DRP1-mediated mitochondrial fission

Acute kidney injury (AKI) is a serious threat to human health. Clinically, ischemia-reperfusion (I/R) injury is considered one of the most common contributors to AKI. Emodin has been reported to alleviate I/R injury in the heart, brain, and small intestine in rats and mice through its anti-inflammatory effects. The present study investigated whether emodin improved AKI induced by I/R and elucidated the molecular mechanisms. We used a mouse model of renal I/R injury and human renal tubular epithelial cell model of hypoxia/reoxygenation (H/R) injury. Ischemia/reperfusion resulted in renal dysfunction. Pretreatment with emodin ameliorated renal injury in mice following I/R injury. Emodin reduced mitochondrial-mediated apoptosis, suppressed the overproduction of mitochondrial reactive oxygen species and accelerated the recovery of adenosine triphosphate both in vivo and in vitro. Emodin prevented mitochondrial fission and restored the balance of mitochondrial dynamics. The phosphorylation of dynamin-related protein 1 (DRP1) at Ser616, a master regulator of mitochondrial fission, was upregulated in both models of I/R and H/R injury, and this upregulation was blocked by emodin. Using computational cognate protein kinase prediction and specific kinase inhibitors, we found that emodin inhibited the phosphorylation of calcium/calmodulin-dependent protein kinase II (https://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=1554), thereby inhibiting its kinase activity and reducing the phosphorylation of DRP1 at Ser616. The results demonstrated that emodin pretreatment could protect renal function by improving mitochondrial dysfunction induced by I/R.

CaMKII-δ9 Induces Cardiomyocyte Death to Promote Cardiomyopathy and Heart Failure

Heart failure is a syndrome in which the heart cannot pump enough blood to meet the body's needs, resulting from impaired ventricular filling or ejection of blood. Heart failure is still a global public health problem and remains a substantial unmet medical need. Therefore, it is crucial to identify new therapeutic targets for heart failure. Ca²⁺/calmodulin-dependent kinase II (CaMKII) is a serine/threonine protein kinase that modulates various cardiac diseases. CaMKII-δ9 is the most abundant CaMKII-δ splice variant in the human heart and acts as a central mediator of DNA damage and cell death in cardiomyocytes. Here, we proved that CaMKII-δ9 mediated cardiomyocyte death promotes cardiomyopathy and heart failure. However, CaMKII-δ9 did not directly regulate cardiac hypertrophy. Furthermore, we also showed that CaMKII-δ9 induced cell death in adult cardiomyocytes through impairing the UBE2T/DNA repair signaling. Finally, we demonstrated no gender difference in the expression of CaMKII-δ9 in the hearts, together with its related cardiac pathology. These findings deepen our understanding of the role of CaMKII-δ9 in cardiac pathology and provide new insights into the mechanisms and therapy of heart failure.

Upregulation of NADPH Oxidase 2 Contributes to Renal Fibrosis in Mice: An Experimental Model of Nephronophthisis

<b><i>Background:</i></b> DBA/2FG-<i>pcy</i> (<i>pcy</i>) mice harbor a homozygous <i>Nphp3</i> missense mutation and develop nephronophthisis with renal interstitial fibrosis. Previous studies have shown that aberrant oxygen homeostasis contributes to the renal pathology in <i>pcy</i> mice, but the underlying molecular mechanism remains largely unknown. <b><i>Methods:</i></b> <i>pcy</i> mice and a control strain, DBA/2N (DBA) mice, were used. Renal levels of 62 mRNAs involved in oxygen homeostasis were investigated by real-time PCR, and the resulting data were used for extraction of pathological pathways. On the basis of the genes found to be upregulated and pathway analysis, further studies were performed using immunoblotting, immunohistochemistry, and pharmacological intervention. <b><i>Results:</i></b> In comparison with DBA mice, the levels of 18 mRNAs were altered by &#x3e;2-fold in <i>pcy</i> mice. Pathway analysis extracted molecular pathways related to oxidative stress, inflammation, and cell adhesion. As the levels of mRNAs relevant to the NADPH oxidase 2 (NOX2) pathway were prominently (4 genes &#x3e;5-fold) increased in <i>pcy</i> mice, we further analyzed the molecules related to this pathway. A time course study suggested that the pathway was gradually activated in <i>pcy</i> mice from at least 5 weeks of age. Immunohistochemistry study revealed that NOX2 protein was colocalized with a macrophage marker protein in the renal interstitium. Moreover, treatment of <i>pcy</i> mice with apocynin, an inhibitor of the NOX2 pathway, ameliorated the renal fibrosis. <b><i>Conclusion:</i></b> Our findings suggest that the activation of the NOX2 pathway, possibly mediated by macrophage infiltration, plays a pivotal role in progressive renal fibrosis in <i>pcy</i> mice.

Role of Polyphenols on Gut Microbiota and the Ubiquitin-Proteasome System in Neurodegenerative Diseases

Today, neurodegenerative diseases have become a remarkable public health challenge due to their direct relation with aging. Accordingly, understanding the molecular and cellular mechanisms occurring in the pathogenesis of them is essential. Both protein aggregations as a result of the ubiquitin-proteasome system (UPS) inefficiency and gut microbiota alternation are the main pathogenic hallmarks. Polyphenols upregulating this system may decrease the developing rate of neurodegenerative diseases. Most of the dietary intake of polyphenols is converted into other microbial metabolites, which have completely different biological properties from the original polyphenols and should be thoroughly investigated. Herein, several prevalent neurodegenerative diseases are pinpointed to explain the role of gut microbiota alternations and the role of molecular changes, especially UPS down-regulation in their pathogenesis. Some of the most important polyphenols found in our diet are explained along with their microbial metabolites in the body.

Renal Ciliopathies: Sorting Out Therapeutic Approaches for Nephronophthisis

Nephronophthisis (NPH) is an autosomal recessive ciliopathy and a major cause of end-stage renal disease in children. The main forms, juvenile and adult NPH, are characterized by tubulointerstitial fibrosis whereas the infantile form is more severe and characterized by cysts. NPH is caused by mutations in over 20 different genes, most of which encode components of the primary cilium, an organelle in which important cellular signaling pathways converge. Ciliary signal transduction plays a critical role in kidney development and tissue homeostasis, and disruption of ciliary signaling has been associated with cyst formation, epithelial cell dedifferentiation and kidney function decline. Drugs have been identified that target specific signaling pathways (for example cAMP/PKA, Hedgehog, and mTOR pathways) and rescue NPH phenotypes in in vitro and/or in vivo models. Despite identification of numerous candidate drugs in rodent models, there has been a lack of clinical trials and there is currently no therapy that halts disease progression in NPH patients. This review covers the most important findings of therapeutic approaches in NPH model systems to date, including hypothesis-driven therapies and untargeted drug screens, approached from the pathophysiology of NPH. Importantly, most animal models used in these studies represent the cystic infantile form of NPH, which is less prevalent than the juvenile form. It appears therefore important to develop new models relevant for juvenile/adult NPH. Alternative non-orthologous animal models and developments in patient-based in vitro model systems are discussed, as well as future directions in personalized therapy for NPH.

Effects of extracellular vesicles from mesenchymal stem cells on oxygen-glucose deprivation/reperfusion-induced neuronal injury

BACKGROUND

Small extracellular vesicles (sEVs) from bone marrow mesenchymal stem cells (BMSCs) have shown therapeutic potential for cerebral ischemic diseases. However, the mechanisms by which BMSC-derived sEVs (BMSC-sEVs) protect neurons against cerebral ischemia/reperfusion (I/R) injury remain unclear. In this study, we explored the neuroprotective effects of BMSC-sEVs in the primary culture of rat cortical neurons exposed to oxygen-glucose deprivation and reperfusion (OGD/R) injury.

METHODS

The primary cortical neuron OGD/R model was established to simulate the process of cerebral I/R in vitro. Based on this model, we examined whether the mechanism through which BMSC-sEVs could rescue OGD/R-induced neuronal injury.

RESULTS

BMSC-sEVs (20 μg/mL, 40 μg/mL) significantly decreased the reactive oxygen species (ROS) productions, and increased the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx). Additionally, BMSC-sEVs prevented OGD/R-induced neuronal apoptosis in vivo, as indicated by increased cell viability, reduced lactate dehydrogenase (LDH) leakage, decreased terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) staining-positive cells, down-regulated cleaved caspase-3, and up-regulated Bcl-2/Bax ratio. Furthermore, Western blot and flow cytometry analysis indicated that BMSC-sEV treatment decreased the expression of phosphorylated calcium/calmodulin-dependent kinase II (p-CaMK II)/CaMK II, suppressed the increase of intracellular calcium concentration ([Ca²⁺]_i) caused by OGD/R in neurons.

CONCLUSIONS

These results demonstrate that BMSC-sEVs have significant neuroprotective effects against OGD/R-induced cell injury by suppressing oxidative stress and apoptosis, and Ca²⁺/CaMK II signaling pathways may be involved in this process.

CaMKII as a key regulator of contrast-induced nephropathy through mPTP opening in HK-2 cells

Contrast-induced nephropathy (CIN), refers to acute kidney injury observed after administration of contrast media during angiographic or other medical procedures such as urography, and accounting for 12% of all causes of acute renal failure, but no specific prevention or treatment strategy exists for its obscure pathophysiology. The aim of our study was to explore the influence of calcium/calmodulin-dependent protein kinase II (CaMKII) in CIN by using HK-2 cells. Knockdown of CypD was achieved by lentivirus, and CaMKII overexpression by transfection with the plasmid. In this study, we have demonstrated that CypD-mediated mPTP opening triggered mitochondrial dysfunction and tubule cells apoptosis in CIN. We also found that iohexol treatment was associated with mitochondrial ROS overloading, ATP depletion and LDH release. Inhibition of CypD with the pharmacologic inhibitor or knockdown of CypD abrogated mPTP opening, oxidative stress, mitochondria damage, and cell apoptosis induced by iohexol. In addition, we found that inhibition of the CaMKII activity alleviated iohexol-induced CypD expression, whereas also decreased mPTP opening, oxidative stress, mitochondria damage, and cell apoptosis, similarly to the inhibition of CypD did. Moreover, CaMKII overexpression enhanced iohexol-induced mPTP opening, mitochondrial damage and renal tubular epithelial cells apoptosis. These findings first identified the novel role of CaMKII in iohexol-induced tubular cells apoptosis and delineated the CaMKII-CypD/mPTP pathway during contrast-induced tubular cell damage. Hence, these results could provide a new strategy for CIN protection.

The oral Ca/calmodulin-dependent kinase II inhibitor RA608 improves contractile function and prevents arrhythmias in heart failure

Aims

Excessive activation of Ca/calmodulin‐dependent kinase II (CaMKII) is of critical importance in heart failure (HF) and atrial fibrillation. Unfortunately, lack of selectivity, specificity, and bioavailability have slowed down development of inhibitors for clinical use. We investigated a novel CaMKIIδ/CaMKIIɣ‐selective, ATP‐competitive, orally available CaMKII inhibitor (RA608) on right atrial biopsies of 119 patients undergoing heart surgery. Furthermore, we evaluated its oral efficacy to prevent deterioration of HF in mice after transverse aortic constriction (TAC).

Methods and results

In human atrial cardiomyocytes and trabeculae, respectively, RA608 significantly reduced sarcoplasmic reticulum Ca leak, reduced diastolic tension, and increased sarcoplasmic reticulum Ca content. Patch‐clamp recordings confirmed the safety of RA608 in human cardiomyocytes. C57BL6/J mice were subjected to TAC, and left ventricular function was monitored by echocardiography. Two weeks after TAC, RA608 was administered by oral gavage for 7 days. Oral RA608 treatment prevented deterioration of ejection fraction. At 3 weeks after TAC, ejection fraction was 46.1 ± 3.7% (RA608) vs. 34.9 ± 2.6% (vehicle), n = 9 vs. n = 12, P < 0.05, ANOVA, which correlated with significantly less CaMKII autophosphorylation at threonine 287. Moreover, a single oral dose significantly reduced inducibility of atrial and ventricular arrhythmias in CaMKIIδ transgenic mice 4 h after administration. Atrial fibrillation was induced in 6/6 mice for vehicle vs. 1/7 for RA608, P < 0.05, 'n − 1'  χ² test. Ventricular tachycardia was induced in 6/7 for vehicle vs. 2/7 for RA608, P < 0.05, 'n − 1'  χ² test.

Conclusions

RA608 is the first orally administrable CaMKII inhibitor with potent efficacy in human myocytes. Moreover, oral administration potently inhibits arrhythmogenesis and attenuates HF development in mice in vivo.

Oxidative Stress and Mitochondrial Abnormalities Contribute to Decreased Endothelial Nitric Oxide Synthase Expression and Renal Disease Progression in Early Experimental Polycystic Kidney Disease

Vascular abnormalities are the most important non-cystic complications in Polycystic Kidney Disease (PKD) and contribute to renal disease progression. Endothelial dysfunction and oxidative stress are evident in patients with ADPKD, preserved renal function, and controlled hypertension. The underlying biological mechanisms remain unknown. We hypothesized that in early ADPKD, the reactive oxygen species (ROS)-producing nicotinamide adenine dinucleotide phosphate hydrogen (NAD(P)H)-oxidase complex-4 (NOX4), a major source of ROS in renal tubular epithelial cells (TECs) and endothelial cells (ECs), induces EC mitochondrial abnormalities, contributing to endothelial dysfunction, vascular abnormalities, and renal disease progression. Renal oxidative stress, mitochondrial morphology (electron microscopy), and NOX4 expression were assessed in 4- and 12-week-old PCK and Sprague-Dawley (wild-type, WT) control rats (n = 8 males and 8 females each). Endothelial function was assessed by renal expression of endothelial nitric oxide synthase (eNOS). Peritubular capillaries were counted in hematoxylin-eosin (H&E)-stained slides and correlated with the cystic index. The enlarged cystic kidneys of PCK rats exhibited significant accumulation of 8-hydroxyguanosine (8-OHdG) as early as 4 weeks of age, which became more pronounced at 12 weeks. Mitochondria of TECs lining cysts and ECs exhibited loss of cristae but remained preserved in non-cystic TECs. Renal expression of NOX4 was upregulated in TECs and ECs of PCK rats at 4 weeks of age and further increased at 12 weeks. Contrarily, eNOS immunoreactivity was lower in PCK vs. WT rats at 4 weeks and further decreased at 12 weeks. The peritubular capillary index was lower in PCK vs. WT rats at 12 weeks and correlated inversely with the cystic index. Early PKD is associated with NOX4-induced oxidative stress and mitochondrial abnormalities predominantly in ECs and TECs lining cysts. Endothelial dysfunction precedes capillary loss, and the latter correlates with worsening of renal disease. These observations position NOX4 and EC mitochondria as potential therapeutic targets in PKD.

Glycosphingolipid metabolism and polycystic kidney disease

Sphingolipids and glycosphingolipids are classes of structurally and functionally important lipids that regulate multiple cellular processes, including membrane organization, proliferation, cell cycle regulation, apoptosis, transport, migration, and inflammatory signalling pathways. Imbalances in sphingolipid levels or subcellular localization result in dysregulated cellular processes and lead to the development and progression of multiple disorders, including polycystic kidney disease. This review will describe metabolic pathways of glycosphingolipids with a focus on the evidence linking glycosphingolipid mediated regulation of cell signalling, lipid microdomains, cilia, and polycystic kidney disease. We will discuss molecular mechanisms of glycosphingolipid dysregulation and their impact on cystogenesis. We will further highlight how modulation of sphingolipid metabolism can be translated into new approaches for the treatment of polycystic kidney disease and describe current clinical studies with glucosylceramide synthase inhibitors in Autosomal Dominant Polycystic Kidney Disease.

Imbalanced mitochondrial function provokes heterotaxy via aberrant ciliogenesis

About 1% of all newborns are affected by congenital heart disease (CHD). Recent findings identify aberrantly functioning cilia as a possible source for CHD. Faulty cilia also prevent the development of proper left-right asymmetry and cause heterotaxy, the incorrect placement of visceral organs. Intriguingly, signaling cascades such as mTor that influence mitochondrial biogenesis also affect ciliogenesis, and can cause heterotaxy-like phenotypes in zebrafish. Here, we identify levels of mitochondrial function as a determinant for ciliogenesis and a cause for heterotaxy. We detected reduced mitochondrial DNA content in biopsies of heterotaxy patients. Manipulation of mitochondrial function revealed a reciprocal influence on ciliogenesis and affected cilia-dependent processes in zebrafish, human fibroblasts and Tetrahymena thermophila. Exome analysis of heterotaxy patients revealed an increased burden of rare damaging variants in mitochondria-associated genes as compared to 1000 Genome controls. Knockdown of such candidate genes caused cilia elongation and ciliopathy-like phenotypes in zebrafish, which could not be rescued by RNA encoding damaging rare variants identified in heterotaxy patients. Our findings suggest that ciliogenesis is coupled to the abundance and function of mitochondria. Our data further reveal disturbed mitochondrial function as an underlying cause for heterotaxy-linked CHD and provide a mechanism for unexplained phenotypes of mitochondrial disease.

Mitochondrial ALDH2 protects against lipopolysaccharide-induced myocardial contractile dysfunction by suppression of ER stress and autophagy

Lipopolysaccharide (LPS), an essential component of outer membrane of the Gram-negative bacteria, plays a pivotal role in myocardial anomalies in sepsis. Recent evidence depicted an essential role for mitochondrial aldehyde dehydrogenase (ALDH2) in cardiac homeostasis. This study examined the effect of ALDH2 on endotoxemia-induced cardiac anomalies. Echocardiographic, cardiac contractile and intracellular Ca²⁺ properties were examined. Our results indicated that LPS impaired cardiac contractile function (reduced fractional shortening, LV end systolic diameter, peak shortening, maximal velocity of shortening/relengthening, prolonged relengthening duration, oxidation of SERCA, and intracellular Ca²⁺ mishandling), associated with ER stress, inflammation, O₂^- production, increased autophagy, CAMKKβ, phosphorylated AMPK and suppressed phosphorylation of mTOR, the effects of which were significantly attenuated or negated by ALDH2. LPS promoted early endosomal formation (as evidenced by RAB4 and RAB5a), apoptosis and necrosis (MTT and LDH) while decreasing late endosomal formation (RAB7 and RAB 9), the effects were reversed by ALDH2. In vitro study revealed that LPS-induced SERCA oxidation, autophagy and cardiac dysfunction were abrogated by ALDH2 activator Alda-1, the ER chaperone TUDCA, the autophagy inhibitor 3-MA, or the AMPK inhibitor Compound C. The beneficial effect of Alda-1 against LPS was nullified by AMPK activator AICAR or rapamycin. CAMKKβ inhibition failed to rescue LPS-induced ER stress. Tunicamycin-induced cardiomyocyte dysfunction was ameliorated by Alda-1 and autophagy inhibition, the effect of which was abolished by rapamycin. These data suggested that ALDH2 protected against LPS-induced cardiac anomalies via suppression of ER stress, autophagy in a CAMKKβ/AMPK/mTOR-dependent manner.

Inhibition of Calcium/Calmodulin-Dependent Protein Kinase IIα Suppresses Oxidative Stress in Cerebral Ischemic Rats Through Targeting Glucose 6-Phosphate Dehydrogenase

Ischemic stroke is a leading cause of mortality and morbidity worldwide, and oxidative stress plays a significant role in the ischemia stage and reperfusion stage. Previous studies have indicated that both calcium/calmodulin-dependent protein kinase II (CaMKII) and glucose 6-phosphate dehydrogenase (G6PD) are involved in the oxidative stress. Thus, the aim of this study was to investigate the roles of CaMKIIα, an important isoform of CaMKII, and G6PD in a rat model of middle cerebral artery occlusion (MCAO). Intracerebroventricular injection of small interfering ribonucleic acid (siRNA) for CaMKIIα was performed at 48 h pre-MCAO surgery. Immunofluorescence Staining and western blot were performed to detect the expression of p-CaMKIIα and G6PD in the cortices. 2, 3, 5-Triphenyltetrazolium chloride (TTC) staining was performed to investigate the infarct volume. In addition, neurological deficit, reactive oxygen species (ROS), ratio of reduced-to-oxidized glutathione (GSH/GSSG) and ratio of reduced-to-oxidized oxidized nicotinamide adenine dinucleotide phosphate (NADPH/NADP⁺) were assessed. The results indicated that both p-CaMKIIα and G6PD were widely located in the neurons and astrocytes, and their expression was gradually increased in the cortices after MCAO, which was accompanied by increased level of ROS and decreased levels of GSH/GSSG and NADPH/NADP⁺. However, after treatment with siRNA for CaMKIIα, p-CaMKIIα expression was decreased and G6PD expression was increased. Moreover, inhibition of CaMKIIα improved the neurological deficit, reduced the infarct volume, decreased the level of ROS and increased the levels of GSH/GSSG and NADPH/NADP⁺. The results suggested that CaMKIIα inhibition exerted neuroprotective effects through regulating G6PD expression, which provides a new target for prevention and treatment of stroke.

ZnSO4 rescued vimentin from collapse in DBP-exposed Sertoli cells by attenuating ER stress and apoptosis

Sertoli cells (SCs) provide physical and nutritional support for spermatogenesis. Dibutyl phthalate (DBP) is a plasticizer that has male reproductive toxicity. The collapse of vimentin in DBP-exposed SCs is thought to induce the sloughing of spermatocytes from seminiferous tubules. In this study, we explored methods to rescue vimentin from collapse in DBP-exposed SCs. DBP not only induced the hyperphosphorylation of vimentin but also triggered endoplasmic reticulum (ER) stress and apoptosis in SCs. Treatment with BAPTA-AM, an antagonist of Ca²⁺, significantly decreased the level of phosphorylated vimentin, while LY294002, an inhibitor of Akt1, did not. ER stress and apoptosis remained at high levels, and the distribution of vimentin was not improved. ZnSO₄ treatment did not decrease the level of phosphorylated vimentin. However, after treatment, ER stress and apoptosis were obviously inhibited, and the distribution of vimentin was reconverted. These results indicated that ZnSO₄ could alleviate the collapse of vimentin by attenuating ER stress and apoptosis. This study suggested that an appropriate zinc supply might be a choice to alleviate DBP-induced adverse reproductive effects.

CaMKⅡ mediates cadmium induced apoptosis in rat primary osteoblasts through MAPK activation and endoplasmic reticulum stress

Ca²⁺ is an important ion in various intracellular metabolic pathways. Endoplasmic reticulum (ER) is a major intracellular calcium store and ER calcium homeostasis plays a key part in the regulation of apoptosis. We have previously shown that Cadmium (Cd) induces apoptosis in osteoblasts (OBs), accompany by increased cytoplasmic calcium. As the role of calcium in OBs apoptosis induced by Cd has not been clarified we investigated the effects of Cd exposure in rat OBs on intracellular Ca²⁺, CaMKII phosphorylation, and the pathways implicated in inducing apoptosis. The results showed that cadmium(Cd) induced elevation of intracellular Ca²⁺ ([Ca²⁺]_i) in OBs by the release of Ca²⁺ from ER and the inflow of Ca²⁺ from the extracellular matrix. Cd induced [Ca²⁺]_i elevation and phosphorylation of CaMKII which might be involved in activation of MAPKs and participated in Cd-induced mitochondrial apoptosis through the alteration of the ratio of Bax/Bcl-2 expression. Meanwhile, CaMKII phosphorylation activated unfolded protein response (UPR) during cadmium treatment and could enable the ER apoptosis pathway through the activation of caspase-12. These results indicated that CaMKII plays an important role in Cd induced ER apoptosis and MAPK activation. Our data provide new insights into the mechanisms underlying apoptosis in OBs following Cd exposure. This provides a theoretical basis for future investigations into the clinical therapeutic application of CaMKⅡ inhibitors in osteoporosis induced by Cd exposure.

CaMKII is involved in subcellular Ca2+ redistribution-induced endoplasmic reticulum stress leading to apoptosis in primary cultures of rat proximal tubular cells exposed to lead

Lead (Pb) is a known nephrotoxic element. Recently we have proved that subcellular Ca²⁺ redistribution is involved in Pb-induced apoptosis in primary cultures of rat proximal tubular (rPT) cells, but the underlying mechanism remains to be elucidated. Firstly, data showed that Pb triggers endoplasmic reticulum (ER) stress response in rPT cells, as evidenced by the elevations of ER stress markers. Moreover, pharmacological modulation of Ca²⁺ mobilization in ER and cytoplasm with three chemicals (2-APB or TG or BAPTA-AM) can effectively increase or decrease the protein expression of ER stress markers in Pb-exposed rPT cells, demonstrating that Pb-induced ER stress is Ca²⁺-dependent. We found that Pb stimulates phosphorylation of calcium/calmodulin-dependent protein kinase II (CaMKII) to activate its activity. Meanwhile, inhibition of CaMKII with KN93 or KN62 attenuated Pb-activated caspase-12 and CCAAT/enhancer-binding protein homologous protein (CHOP) in rPT cells, demonstrating that CaMKII activation promoted ER stress in rPT cells. Likewise, Pb-induced apoptosis can be effectively inhibited by CaMKII inhibitor KN93 or KN62. Furthermore, co-treatment with KN93 or KN62 significantly reversed Pb-induced ER Ca²⁺ release and concomitant intracellular Ca²⁺ overload in rPT cells. In summary, these results expound the mechanisms involving in ER stress, Ca²⁺ dyshomeostasis and activated CaMKII, which all contribute to Pb-induced apoptosis. CaMKII acts as a critical mediator of ER stress and associated apoptosis via regulating intracellular Ca²⁺ mobilization from ER to cytoplasm.

CaMKII is a nodal signal for multiple programmed cell death pathways in heart

Sustained Ca2+/calmodulin-dependent kinase II (CaMKII) activation plays a central role in the pathogenesis of a variety of cardiac diseases. Emerging evidence suggests CaMKII evoked programmed cell death, including apoptosis and necroptosis, is one of the key underlying mechanisms for the detrimental effect of sustained CaMKII activation. CaMKII integrates β-adrenergic, Gq coupled receptor, reactive oxygen species (ROS), hyperglycemia, and pro-death cytokine signaling to elicit myocardial apoptosis by intrinsic and extrinsic pathways. New evidence demonstrates CaMKII is also a key mediator of receptor interacting serine/threonine kinase 3 (RIP3)-induced myocardial necroptosis. The role of CaMKII in cell death is dependent upon subcellular localization and varies across isoforms and splice variants. While CaMKII is now an extensively validated nodal signal for promoting cardiac myocyte death, the upstream and downstream pathways and targets remain incompletely understood, demanding further investigation.

Endoplasmic reticulum stress and calcium imbalance are involved in cadmium-induced lipid aberrancy in Saccharomyces cerevisiae

The endoplasmic reticulum is the key organelle which controls protein folding, lipid biogenesis, and calcium (Ca(2+)) homeostasis. Cd exposure in Saccharomyces cerevisiae activated the unfolded protein response and was confirmed by the increased Kar2p expression. Cd exposure in wild-type (WT) cells increased PC levels and the PC biosynthetic genes. Deletion of the two phospholipid methyltransferases CHO2 and OPI3 modulated PC, TAG levels and the lipid droplets with cadmium exposure. Interestingly, we noticed an increase in the calcium levels upon Cd exposure in the mutant cells. This study concluded that Cd interrupted calcium homeostasis-induced lipid dysregulation leading to ER stress.