Biology subjects

Qaisar, R.

Publications and source records attributed to Qaisar, R..

4 recordsLinked to original sources

bioRxiv2024

GSK-3alpha-BNIP3 axis promotes mitophagy in human cardiomyocytes under hypoxia

Dysregulated autophagy/mitophagy is one of the major causes of cardiac injury in ischemic conditions. Glycogen synthase kinase-3alpha (GSK-3) has been shown to play a crucial role in the pathophysiology of cardiac diseases. However, the precise role of GSK-3 in cardiac mitophagy remains unknown. Herein, we investigated the role of GSK-3 in cardiac mitophagy by employing AC16 human cardiomyocytes under the condition of acute hypoxia. We observed that the gain-of-GSK-3 function profoundly induced mitophagy in the AC16 cardiomyocytes post-hypoxia. Moreover, GSK-3 overexpression led to increased ROS generation and mitochondrial dysfunction in cardiomyocytes, accompanied by enhanced mitophagy displayed by increased mt-mKeima intensity under hypoxia. Mechanistically, we identified that GSK-3 promotes mitophagy through upregulation of BNIP3, caused by GSK-3-mediated increase in expression of HIF-1 and FOXO3a in cardiomyocytes post-hypoxia. Moreover, GSK-3 displayed a physical interaction with BNIP3 and, inhibited PINK1 and Parkin recruitment to mitochondria was observed specifically under hypoxia. Taken together, we identified a novel mechanism of mitophagy in human cardiomyocytes. GSK-3 promotes mitochondrial dysfunction and regulates FOXO3a -mediated BNIP3 overexpression in cardiomyocytes to facilitate mitophagy following hypoxia. An interaction between GSK-3 and BNIP3 suggests a role of GSK-3 in BNIP3 recruitment to the mitochondrial membrane where it enhances mitophagy in stressed cardiomyocytes independent of the PINK1/Parkin.

cell biology↗

bioRxiv2024

Natural compound screening predicts novel GSK-3 isoform-specific inhibitors

Glycogen synthase kinase-3 (GSK-3) plays important roles in the pathogenesis of cardiovascular, metabolic, neurological disorders and cancer. Isoform-specific loss of either GSK-3 or GSK-3{beta} often provides cytoprotective effects under such clinical conditions. However, available synthetic small molecule inhibitors are relatively non-specific, and their chronic use may lead to adverse effects. Therefore, screening for natural compound inhibitors to identify the isoform-specific inhibitors may provide improved clinical utility. Here, we screened 70 natural compounds to identify novel natural GSK-3 inhibitors employing comprehensive in silico and biochemical approaches. Molecular docking and pharmacokinetics analysis identified two natural compounds Psoralidin and Rosmarinic acid as potential GSK-3 inhibitors. Specifically, Psoralidin and Rosmarinic acid exhibited the highest binding affinities for GSK-3 and GSK-3{beta}, respectively. Consistent with in silico findings, the kinase assay-driven IC50 revealed superior inhibitory effects of Psoralidin against GSK-3 (IC50=2.26 {micro}M) vs. GSK-3{beta} (IC50=4.23 {micro}M) while Rosmarinic acid was found to be more potent against GSK-3{beta} (IC50=2.24 {micro}M) than GSK-3 (IC50=5.14 {micro}M). Taken together, these studies show that the identified natural compounds may serve as GSK-3 inhibitors with Psoralidin serving as a better inhibitor for GSK-3 and Rosmarinic for GSK-3{beta} isoform, respectively. Further characterization employing in vitro and preclinical models will be required to test the utility of these compounds as GSK-3 inhibitors for cardiometabolic and neurological disorders and cancers. HighlightsO_LICurrent GSK-3 inhibitors lack specificity and cause side effects. C_LIO_LIThis study identifies potential GSK-3 isoform-specific natural compounds. C_LIO_LIPsoralidin is likely a better inhibitor for GSK-3 while Rosmarinic for GSK-3{beta}. C_LIO_LIThese natural compounds may be promising future treatments. C_LI

biochemistry↗

bioRxiv2021

Nicotinamide riboside kinase-2 inhibits JNK pathway and limits dilated cardiomyopathy in mice with chronic pressure overload

Nicotinamide riboside kinase-2 (NRK-2) has recently emerged as a critical regulator of cardiac remodeling however, underlying molecular mechanisms is largely unknown. To explore the same, NRK2 knockout (KO) and littermate control mice were subjected to trans-aortic constriction (TAC) or sham surgeries and cardiac function was assessed by serial M-mode echocardiography. A mild cardiac contractile dysfunction was observed in the KOs at the early adaptive phase of remodeling followed by a significant deterioration during the maladaptive cardiac remodeling phase. Consistently, NRK2 KO hearts displayed increased cardiac hypertrophy and heart failure reflected by morphometric parameters as well as increased fetal genes ANP and BNP expressions. Histological assessment revealed an extensive left ventricular (LV) chamber dilatation accompanied by elevated cardiomyopathy and fibrosis in the KO hearts post-TAC. In a gain-of-function model, NRK-2 overexpressing in AC16 cardiomyocytes displayed significantly attenuated fetal genes ANP and BNP expression. Consistently, NRK-2 overexpression attenuated angiotensin II-induced cardiomyocyte death. Mechanistically, we identified NRK-2 as a regulator of JNK MAP kinase and mitochondrial function where NRK-2 overexpression in human cardiomyocytes markedly suppressed the angiotensin II-induced JNK activation and mitochondrial depolarization. Thus, our results demonstrate that NRK-2 plays protective roles in pressure overload-induced dilatative cardiac remodeling and, genetic ablation exacerbates dilated cardiomyopathy, interstitial collagen deposition, and cardiac dysfunction post-TAC due, in part, to increased JNK activation and mitochondrial dysfunction.

molecular biology↗

bioRxiv2021

Cardiomyocyte GSK-3β deficiency induces cardiac progenitor cell proliferation in the ischemic heart through paracrine mechanisms

Cardiomyopathy is an irreparable loss and novel strategies are needed to induce resident cardiac progenitor cell (CPC) proliferation in situ to enhance the possibility of cardiac regeneration. Here we sought to identify the potential roles of glycogen synthase kinase-3{beta} (GSK-3{beta}), a critical regulator of cell proliferation and differentiation, in CPC proliferation post-myocardial infarction (MI). Cardiomyocyte-specific conditional GSK-3{beta} knockout (cKO) and littermate control mice were employed and challenged with MI. Though cardiac left ventricular chamber dimension (LVID) and contractile functions were comparable at two-week post-MI, cKO mice displayed significantly preserved LV chamber and contractile function vs. control mice at four-weeks post-MI. Consistent with protective phenotypes, an increased percentage of c-kit-positive cells (KPCs) were observed in the cKO hearts at four and six-weeks post-MI which was accompanied by increased levels of cardiomyocyte proliferation. Further analysis revealed that the observed increased number of KPCs in the ischemic cKO hearts was mainly from a cardiac lineage as the majority of identified KPCs were negative for the hematopoietic lineage marker, CD45. Mechanistically, cardiomyocyte-GSK-3{beta} profoundly suppresses the expression and secretion of growth factors, including basic-FGF angiopoietin-2, erythropoietin, stem cell factor (SCF), PDGF-BB, G-CSF, and VEGF, post-hypoxia. In conclusion, our findings strongly suggest that loss of cardiomyocyte-GSK-3{beta} promotes cardiomyocyte and resident CPC proliferation post-MI. The induction of cardiomyocyte and CPC proliferation in the ischemic cKO hearts is potentially regulated by autocrine and paracrine signaling governed by dysregulated growth factors post-MI. A strategy to inhibit cardiomyocyte GSK-3{beta} could be helpful for the promotion of in situ cardiac regeneration post-ischemic injury.

molecular biology↗