Evaluation of mitochondrial oxidative toxicity in mammalian cardiomyocytes by determining the highly reproducible and reliable increase in mitochondrial superoxides after exposure to therapeutic drugs

NLRP3 inflammasome-mitochondrion loop in autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social communication and the presence of restricted interests and repetitive behavior. To date, no single cause has been demonstrated but both genetic and environmental factors are believed to be involved in abnormal brain development. In recent years, immunological and mitochondrial dysfunctions acquired particular interest in the study of the molecular mechanisms underlying the pathophysiology of ASD. For this reason, our study focused on evaluating the mitochondrial component and activation of the NLRP3 inflammasome, a critical player of the innate immune system. The assembly of NLRP3 with ASC mediates activation of Caspase-1, which in turn, by proteolytic cleavage, activates Gasdermin D and the proinflammatory cytokines IL-1β/IL-18 with their subsequent secretion. Using primary fibroblasts of autistic and control patients we studied basal and stimulated conditions. Specifically, LPS and ATP were used to activate the NLRP3 inflammasome and MCC950 for its inhibition. In addition, FCCP was used as a mitochondrial stressor and MitoTEMPO as a scavenger of mitochondrial ROS. Our results showed a hyperactivation of NLRP3 inflammasome in ASDs, as evidenced by the co-localization of the two main components, NLRP3 and ASC, by the higher levels of ASC specks, oligomers and dimers and by the increased amounts of active Caspase-1 and IL-1β. In addition, increased mitochondrial superoxide anion and reduced mitochondrial membrane potential were detected in ASD cells. These data are in accordance with the abnormal mitochondrial morphology evidenced by transmission electron microscopy analysis. Interestingly, NLRP3 inflammasome inhibition with MCC950 improved mitochondrial parameters, while the use of MitoTEMPO, in addition to decrease mitochondrial ROS production, was able to prevent NLRP3 inflammasome activation suggesting for the first time an abnormal bidirectional crosstalk between mitochondria and NLRP3 inflammasome in ASD.

Effects of riboflavin in the treatment of brain damage caused by oxygen deprivation: an integrative systematic review

Brain oxygen deprivation causes morphological damage involved in the formation of serious pathological conditions such as stroke and cerebral palsy. Therapeutic methods for post-hypoxia/anoxia injuries are limited and still have deficiencies in terms of safety and efficacy. Recently, clinical studies of stroke have reported the use of drugs containing riboflavin for post-injury clinical rehabilitation, however, the effects of vitamin B2 on exposure to cerebral oxygen deprivation are not completely elucidated. This review aimed to investigate the potential antioxidant, anti-inflammatory and neuroprotective effects of riboflavin in cerebral hypoxia/anoxia. After a systematic search, 21 articles were selected, 8 preclinical and 12 clinical studies, and 1 translational study. Most preclinical studies used B2 alone in models of hypoxia in rodents, with doses of 1-20 mg/kg (in vivo) and 0.5-5 µM (in vitro). Together, these works suggested greater regulation of lipid peroxidation and apoptosis and an increase in neurotrophins, locomotion, and cognition after treatment. In contrast, several human studies have administered riboflavin (5 mg) in combination with other Krebs cycle metabolites, except one study, which used only B2 (20 mg). A reduction in lactic acidosis and recovery of sensorimotor functions was observed in children after treatment with B2, while adults and the elderly showed a reduction in infarct volume and cognitive rehabilitation. Based on findings from preclinical and clinical studies, we conclude that the use of riboflavin alone or in combination acts beneficially in correcting the underlying brain damage caused by hypoxia/anoxia and its inflammatory, oxidative, and behavioral impairments.

Fludioxonil induces cardiotoxicity via mitochondrial dysfunction and oxidative stress in two cardiomyocyte models

Fludioxonil (Flu) is a phenylpyrrole fungicide and is currently used in over 900 agricultural products globally. Flu possesses endocrine-disrupting chemical-like properties and has been shown to mediate various physiological and pathological changes, such as apoptosis and differentiation, in diverse cell lines. However, the effects of Flu on cardiomyocytes have not been studied so far. The present study investigated the effects of Flu on mitochondria in AC16 human cardiomyocytes and H9c2 rat cardiomyoblasts. Flu decreased cell viability in a water-soluble tetrazolium assay and mediated morphological changes suggestive of apoptosis in AC16 and H9c2 cells. We confirmed that annexin V positive cells were increased by Flu through annexin V/propidium iodide staining. This suggests that the decrease in cell viability due to Flu may be associated with increased apoptotic changes. Flu consistently increased the expression of pro-apoptotic markers such as Bcl-2-associated X protein (Bax) and cleaved-caspase 3. Further, Flu reduced the oxygen consumption rate (OCR) in AC16 and H9c2 cells, which is associated with decreased mitochondrial membrane potential (MMP) as observed through JC-1 staining. In addition, Flu augmented the production of mitochondrial reactive oxygen species, which can trigger oxidative stress in cardiomyocytes. Taken together, these results indicate that Flu induces mitochondrial dysregulation in cardiomyocytes via the downregulation of the OCR and MMP and upregulation of the oxidative stress, consequently resulting in the apoptosis of cardiomyocytes. This study provides evidence of the risk of Flu toxicity on cardiomyocytes leading to the development of cardiovascular diseases and suggests that the use of Flu in agriculture should be done with caution and awareness of the probable health consequences of exposure to Flu.

Amiodarone but not propafenone impairs bioenergetics and autophagy of human myocardial cells

Cardiac and extra-cardiac side effects of common antiarrhythmic agents might be related to drug-induced mitochondrial dysfunction. Supratherapeutic doses of amiodarone have been shown to impair mitochondria in animal studies, whilst influence of propafenone on cellular bioenergetics is unknown. We aimed to assess effects of protracted exposure to pharmacologically relevant doses of amiodarone and propafenone on cellular bioenergetics and mitochondrial biology of human and mouse cardiomyocytes. In this study, HL-1 mouse atrial cardiomyocytes and primary human cardiomyocytes derived from the ventricles of the adult heart were exposed to 2 and 7 μg/mL of either amiodarone or propafenone. After 24 h, extracellular flux analysis and confocal laser scanning microscopy were used to measure mitochondrial functions. Autophagy was assessed by western blots and live-cell imaging of lysosomes. In human cardiomyocytes, amiodarone significantly reduced mitochondrial membrane potential and ATP production, in association with an inhibition of fatty acid oxidation and impaired complex I- and II-linked respiration in the electron transport chain. Expectedly, this led to increased anaerobic glycolysis. Amiodarone increased the production of reactive oxygen species and autophagy was also markedly affected. In contrast, propafenone-exposed cardiomyocytes did not exert any impairment of cellular bioenergetics. Similar changes after amiodarone treatment were observed during identical experiments performed on HL-1 mouse cardiomyocytes, suggesting a comparable pharmacodynamics of amiodarone among mammalian species. In conclusion, amiodarone but not propafenone in near-therapeutic concentrations causes a pattern of mitochondrial dysfunction with affected autophagy and metabolic switch from oxidative metabolism to anaerobic glycolysis in human cardiomyocytes.

Microcystin-leucine arginine exhibits adverse effects on human aortic vascular smooth muscle cells in vitro

Microcystin-leucine arginine (MC-LR) is a kind of toxin produced by cyanobacteria, which can do harm to human and livestock health. MC-LR can easily enter tissues and organs through the blood circulation and accumulate in certain target organs. Vessels are prone to contact with MC-LR during growth and development. Previous study had demonstrated that MC-LR had potential vascular toxicity. However, it is not clear whether MC-LR has adverse effects on vascular smooth muscle cells. In this study, we evaluated the cytotoxicity of MC-LR exposure (0.01, 0.05, 0.1, 0.5, and 1 μM) on human aortic vascular smooth muscle cells (HAVSMCs) in vitro. The data showed that MC-LR exposure inhibited the HAVSMC proliferation and migration, induced HAVSMC apoptosis, cytoskeleton destruction, S-phase arrest, mitochondrial transmembrane potential (MMP) loss, and reactive oxygen species (ROS) production. In addition, MC-LR exposure resulted in the imbalance between oxidants and antioxidants, increased the caspase-3 and caspase-9 activities, and down-regulated the gene expressions (integrin β1, Rho, ROCK, MLC). Taken together, MC-LR could induce the generation of ROS in HAVSMCs, leading to apoptosis by the mitochondrial signaling pathway. MC-LR could also induce cytoskeletal disruption by integrin-mediated FAK/ROCK signaling pathway, leading to cell cycle arrest and the inhibition of HAVSMCs proliferation and migration. The current findings facilitate an understanding of the mechanism of MC-LR toxicity involved in angiocardiopathy.