Optimization of measurement of mitochondrial electron transport activity in postmortem human brain samples and measurement of susceptibility to rotenone and 4-hydroxynonenal inhibition

The interplay between sex, time of day, fasting status, and their impact on cardiac mitochondrial structure, function, and dynamics

Mitochondria morphology and function, and their quality control by mitophagy, are essential for heart function. We investigated whether these are influenced by time of the day (TOD), sex, and fed or fasting status, using transmission electron microscopy (EM), mitochondrial electron transport chain (ETC) activity, and mito-QC reporter mice. We observed peak mitochondrial number at ZT8 in the fed state, which was dependent on the intrinsic cardiac circadian clock, as hearts from cardiomyocyte-specific BMAL1 knockout (CBK) mice exhibit different TOD responses. In contrast to mitochondrial number, mitochondrial ETC activities do not fluctuate across TOD, but decrease immediately and significantly in response to fasting. Concurrent with the loss of ETC activities, ETC proteins were decreased with fasting, simultaneous with significant increases of mitophagy, mitochondrial antioxidant protein SOD2, and the fission protein DRP1. Fasting-induced mitophagy was lost in CBK mice, indicating a direct role of BMAL1 in regulating mitophagy. This is the first of its kind report to demonstrate the interactions between sex, fasting, and TOD on cardiac mitochondrial structure, function and mitophagy. These studies provide a foundation for future investigations of mitochondrial functional perturbation in aging and heart diseases.

Sustained Increases in Cardiomyocyte Protein O-Linked β-N-Acetylglucosamine Levels Lead to Cardiac Hypertrophy and Reduced Mitochondrial Function Without Systolic Contractile Impairment

Background Lifestyle and metabolic diseases influence the severity and pathogenesis of cardiovascular disease through numerous mechanisms, including regulation via posttranslational modifications. A specific posttranslational modification, the addition of O-linked β-N acetylglucosamine (O-GlcNAcylation), has been implicated in molecular mechanisms of both physiological and pathologic adaptations. The current study aimed to test the hypothesis that in cardiomyocytes, sustained protein O-GlcNAcylation contributes to cardiac adaptations, and its progression to pathophysiology. Methods and Results Using a naturally occurring dominant-negative O-GlcNAcase (dnOGA) inducible cardiomyocyte-specific overexpression transgenic mouse model, we induced dnOGA in 8- to 10-week-old mouse hearts. We examined the effects of 2-week and 24-week dnOGA overexpression, which progressed to a 1.8-fold increase in protein O-GlcNAcylation. Two-week increases in protein O-GlcNAc levels did not alter heart weight or function; however, 24-week increases in protein O-GlcNAcylation led to cardiac hypertrophy, mitochondrial dysfunction, fibrosis, and diastolic dysfunction. Interestingly, systolic function was maintained in 24-week dnOGA overexpression, despite several changes in gene expression associated with cardiovascular disease. Specifically, mRNA-sequencing analysis revealed several gene signatures, including reduction of mitochondrial oxidative phosphorylation, fatty acid, and glucose metabolism pathways, and antioxidant response pathways after 24-week dnOGA overexpression. Conclusions This study indicates that moderate increases in cardiomyocyte protein O-GlcNAcylation leads to a differential response with an initial reduction of metabolic pathways (2-week), which leads to cardiac remodeling (24-week). Moreover, the mouse model showed evidence of diastolic dysfunction consistent with a heart failure with preserved ejection fraction. These findings provide insight into the adaptive versus maladaptive responses to increased O-GlcNAcylation in heart.

Lapatinib ditosylate rescues motor deficits in rotenone-intoxicated rats: Potential repurposing of anti-cancer drug as a disease-modifying agent in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by motor deficits induced by dopaminergic neuronal death in the substantia nigra (SN). Finding a successful neuroprotective therapy is still challenging despite improved knowledge of the etiology of PD and a variety of medications intended to reduce symptoms. Lapatinib (LAP), an FDA-approved anti-cancer medication, has been stated to exert its effect through the modulation of oxidative stress. Furthermore, recent studies display the neuroprotective effects of LAP in epilepsy, encephalomyelitis, and Alzheimer's disease in rodent models through the modulation of oxidative stress and ferroptosis. Nevertheless, it is questionable whether LAP exerts neuroprotective effects in PD. In the current study, administration of 100 mg/kg LAP in rotenone-treated rats for 21 days ameliorates motor impairment, debilitated histopathological alterations, and revived dopaminergic neurons by increasing tyrosine hydroxylase (TH) expression in SN, along with increased dopamine level. LAP remarkably restored the antioxidant defense mechanism system, GPX4/GSH/NRF2 axis, inhibiting oxidative markers, including iron, TfR1, PTGS2, and 4-HNE, along with suppression of p-EGFR/c-SRC/PKCβII/PLC-γ/ACSL-4 pathway. Moreover, LAP modulates HSP90/CDC37 chaperone complex, regulating many key pathological markers of PD, including LRRK2, c-ABL, and α-syn. It is concluded that LAP has neuroprotective effects in PD via modulation of many key parameters implicated in PD pathogenesis. Taken together, the current study offers insights into the potential repositioning of LAP as a disease-modifying drug in PD.

Cardiomyocyte ZKSCAN3 regulates remodeling following pressure-overload

Autophagy is important for protein and organelle quality control. Growing evidence demonstrates that autophagy is tightly controlled by transcriptional mechanisms, including repression by zinc finger containing KRAB and SCAN domains 3 (ZKSCAN3). We hypothesize that cardiomyocyte-specific ZKSCAN3 knockout (Z3K) disrupts autophagy activation and repression balance and exacerbates cardiac pressure-overload-induced remodeling following transverse aortic constriction (TAC). Indeed, Z3K mice had an enhanced mortality compared to control (Con) mice following TAC. Z3K-TAC mice that survived exhibited a lower body weight compared to Z3K-Sham. Although both Con and Z3K mice exhibited cardiac hypertrophy after TAC, Z3K mice exhibited TAC-induced increase of left ventricular posterior wall thickness at end diastole (LVPWd). Conversely, Con-TAC mice exhibited decreases in PWT%, fractional shortening (FS%), and ejection fraction (EF%). Autophagy genes (Tfeb, Lc3b, and Ctsd) were decreased by the loss of ZKSCAN3. TAC suppressed Zkscan3, Tfeb, Lc3b, and Ctsd in Con mice, but not in Z3K. The Myh6/Myh7 ratio, which is related to cardiac remodeling, was decreased by the loss of ZKSCAN3. Although Ppargc1a mRNA and citrate synthase activities were decreased by TAC in both genotypes, mitochondrial electron transport chain activity did not change. Bi-variant analyses show that while in Con-Sham, the levels of autophagy and cardiac remodeling mRNAs form a strong correlation network, such was disrupted in Con-TAC, Z3K-Sham, and Z3K-TAC. Ppargc1a also forms different links in Con-sham, Con-TAC, Z3K-Sham, and Z3K-TAC. We conclude that ZKSCAN3 in cardiomyocytes reprograms autophagy and cardiac remodeling gene transcription, and their relationships with mitochondrial activities in response to TAC-induced pressure overload.