Mitotherapy as a Novel Therapeutic Strategy for Mitochondrial Diseases

From mitochondrial dysfunction to neuroinflammation in Parkinson's disease: Pathogenesis and mitochondrial therapeutic approaches

Parkinson's disease (PD) is a prevalent and intricate neurological condition resulting from a combination of several factors, such as genetics, environment, and the natural process of aging. Degeneration of neurons in the substantia nigra pars compacta (SN) can cause motor and non-motor impairments in patients with PD. In PD's etiology, inflammation and mitochondrial dysfunction play significant roles in the disease's development. Studies of individuals with PD have revealed increased inflammation in various brain areas. Furthermore, mitochondrial dysfunction is an essential part of PD pathophysiology. Defects in the components of the mitochondrial nucleus, its membrane or internal signaling pathways, mitochondrial homeostasis, and morphological alterations in peripheral cells have been extensively documented in PD patients. According to these studies, neuroinflammation and mitochondrial dysfunction are closely connected as pathogenic conditions in neurodegenerative diseases like PD. Given the mitochondria's role in cellular homeostasis maintenance in response to membrane structural flaws or mutations in mitochondrial DNA, their dynamic nature may present therapeutic prospects in this area. Recent research investigates mitochondrial transplantation as a potential treatment for Parkinson's disease in damaged neurons. This review delves into the impact of inflammation and mitochondrial dysfunction on PD occurrence, treatment approaches, and the latest developments in mitochondrial transplantation, highlighting the potential consequences of these discoveries.

Mitotherapy inhibits against tenofovir induced nephrotoxicity on rat renal proximal tubular cells

Tenofovir, as nucleotide reverse transcriptase inhibitors (NRTIs), is used to prevent and cure HIV/AIDS. Ample evidence confirmed that the nephrotoxicity of tenofovir has been linked to mitochondrial dysfunction. It seems that transplantation with healthy mitochondria instead of damaged mitochondria may be a beneficial approach to therapy. Therefore, it decided to investigate the impact of mitotherapy on tenofovir against renal proximal tubular cells (RPTCs) toxicity by measurement of oxidative stress and cytotoxicity biomarkers and restoring of mitochondrial function on isolated mitochondria. EC50 of tenofovir was achieved at 40 μM following 2 h incubation in Earle's solution (pH = 7.4; 37 °C). Freshly isolated mitochondria (80 μg/ml) were added to damage RPTCs affected by tenofovir in treated groups. One Way ANOVA analysis showed that healthy mitochondrial transplantation decreased oxidative stress biomarkers following tenofovir toxicity in RPTCs. Our data revealed that mitotherapy makes cell survival possible in RPTCs affected by tenofovir. In addition, it supposed that a novel and ideal strategy for the treatment of chemicals-induced nephrotoxicity.

Mitochondrial administration alleviates lead- and cadmium-induced toxicity in rat renal cells

The role of heavy metals such as lead (Pb) and cadmium (Cd) in the etiology of many diseases has been proven. Also, these heavy metals can affect the normal mitochondrial function. Mitochondrial administration therapy is one of the methods used by researchers to help improve mitochondrial defects and diseases. The use of isolated mitochondria as a therapeutic approach has been investigated in in vivo and in vitro studies. Accordingly, in this study, the effects of mitochondrial administration on the improvement of toxicity caused by Pb and Cd in renal proximal tubular cells (RPTC) have been investigated. The results showed that treatment to Pb and Cd caused an increase in the level of free radicals, lipid peroxidation (LPO) content, mitochondrial and lysosomal membrane damage, and also a decrease in the reduced glutathione content in RPTC. In addition, reports have shown an increase in oxidized glutathione content and changes in energy (ATP) levels. Following, the results have shown the protective role of mitochondrial administration in improving the toxicity caused by Pb and Cd in RPTC. Furthermore, the mitochondrial internalization into RPT cells is mediated through actin-dependent endocytosis. So, it could be suggested that the treatment of Pb- and Cd-induced cytotoxicity in RPTC could be carried out through mitochondria administration.

Key hepatoprotective roles of mitochondria in liver regeneration

Treatment of advanced liver disease using surgical modalities is possible due to the liver's innate ability to regenerate following resection. Several key cellular events in the regenerative process converge at the mitochondria, implicating their crucial roles in liver regeneration. Mitochondria enable the regenerating liver to meet massive metabolic demands by coordinating energy production to drive cellular proliferative processes and vital homeostatic functions. Mitochondria are also involved in terminating the regenerative process by mediating apoptosis. Studies have shown that attenuation of mitochondrial activity results in delayed liver regeneration, and liver failure following resection is associated with mitochondrial dysfunction. Emerging mitochondria therapy (i.e., mitotherapy) strategies involve isolating healthy donor mitochondria for transplantation into diseased organs to promote regeneration. This review highlights mitochondria's inherent role in liver regeneration.

Mitochondrial Transfusion Improves Mitochondrial Function Through Up-regulation of Mitochondrial Complex II Protein Subunit SDHB in the Hippocampus of Aged Mice

The mitochondrial theory of aging is characterized by mitochondrial electron transport chain dysfunction. As a hallmark of aging, an increasing number of investigations have attempted to improve mitochondrial function in both aging and age-related disease. Emerging from these attempts, methods involving mitochondrial isolation, transfusion, and transplantation have taken center stage. In particular, mitochondrial transfusion refers to the administration of mitochondria from healthy tissue into the bloodstream or into tissues affected by injury, disease, or aging. In this study, methods of mitochondrial isolation and transfusion were developed and utilized. First, we found a significant decrease (p < 0.05) in the expression of mitochondrial complex proteins (I-V) in aged (12 months old) mouse brain tissue (C57BL/6 mice) in comparison to healthy young brain tissue (1 month old). To investigate whether healthy young mitochondria taken from the liver could improve mitochondrial function in older animals, we intravenously injected mitochondria isolated from young C57BL/6 mice into aged mice from the same strain. This study, for the first time, demonstrates that mitochondrial transfusion significantly (p < 0.05) improves mitochondrial function via the up-regulation of the mitochondrial complex II protein subunit SDHB in the hippocampus of aged mice. This result has identified a role for mitochondrial complex II in the aging process. Therefore, mitochondrial complex II could serve as a putative target for therapeutic interventions against aging. However, more importantly, methods of mitochondrial transfusion should be further tested to treat a variety of human diseases or disorders and to slow down or reverse processes of aging.

Establishment of a platform for measuring mitochondrial oxygen consumption rate for cardiac mitochondrial toxicity

The heart has an abundance of mitochondria since cardiac muscles require copious amounts of energy for providing continuous blood through the circulatory system, thereby implying that myocardial function is largely reliant on mitochondrial energy. Thus, cardiomyocytes are susceptible to mitochondrial dysfunction and are likely targets of mitochondrial toxic drugs. Various methods have been developed to evaluate mitochondrial toxicity by evaluating toxicological mechanisms, but an optimized and standardized assay for cardiomyocytes remains unmet. We have therefore attempted to standardize the evaluation system for determining cardiac mitochondrial toxicity, using AC16 human and H9C2 rat cardiomyocytes. Three clinically administered drugs (acetaminophen, amiodarone, and valproic acid) and two anticancer drugs (doxorubicin and tamoxifen) which are reported to have mitochondrial effects, were applied in this study. The oxygen consumption rate (OCR), which directly reflects mitochondrial function, and changes in mRNA levels of mitochondrial respiratory complex I to complex V, were analyzed. Our results reveal that exposure to all five drugs results in a concentration-dependent decrease in the basal and maximal levels of OCR in AC16 cells and H9C2 cells. In particular, marked reduction in the OCR was observed after treatment with doxorubicin. The reduction in OCR after exposure to mitochondrial toxic drugs was found to be associated with reduced mRNA expression in the mitochondrial respiratory complexes, suggesting that the cardiac mitochondrial toxicity of drugs is majorly due to dysfunction of mitochondrial respiration. Based on the results of this study, we established and standardized a protocol to measure OCR in cardiomyocytes. We expect that this standardized evaluation system for mitochondrial toxicity can be applied as basic data for establishing a screening platform to evaluate cardiac mitochondrial toxicity of drugs, during the developmental stage of new drug discovery.

NADPH Oxidases Connecting Fatty Liver Disease, Insulin Resistance and Type 2 Diabetes: Current Knowledge and Therapeutic Outlook

Nonalcoholic fatty liver disease (NAFLD), characterized by ectopic fat accumulation in hepatocytes, is closely linked to insulin resistance and is the most frequent complication of type 2 diabetes mellitus (T2DM). One of the features connecting NAFLD, insulin resistance and T2DM is cellular oxidative stress. Oxidative stress refers to a redox imbalance due to an inequity between the capacity of production and the elimination of reactive oxygen species (ROS). One of the major cellular ROS sources is NADPH oxidase enzymes (NOX-es). In physiological conditions, NOX-es produce ROS purposefully in a timely and spatially regulated manner and are crucial regulators of various cellular events linked to metabolism, receptor signal transmission, proliferation and apoptosis. In contrast, dysregulated NOX-derived ROS production is related to the onset of diverse pathologies. This review provides a synopsis of current knowledge concerning NOX enzymes as connective elements between NAFLD, insulin resistance and T2DM and weighs their potential relevance as pharmacological targets to alleviate fatty liver disease.

Mitochondria, energy, and metabolism in neuronal health and disease

Mitochondria are associated with various cellular activities critical to homeostasis, particularly in the nervous system. The plastic architecture of the mitochondrial network and its dynamic structure play crucial roles in ensuring that varying energetic demands are rapidly met to maintain neuronal and axonal energy homeostasis. Recent evidence associates ageing and neurodegeneration with anomalous neuronal metabolism, as age-dependent alterations of neuronal metabolism are now believed to occur prior to neurodegeneration. The brain has a high energy demand, which makes it particularly sensitive to mitochondrial dysfunction. Distinct cellular events causing oxidative stress or disruption of metabolism and mitochondrial homeostasis can trigger a neuropathology. This review explores the bioenergetic hypothesis for the neurodegenerative pathomechanisms, discussing factors leading to age-related brain hypometabolism and its contribution to cognitive decline. Recent research on the mitochondrial network in healthy nervous system cells, its response to stress and how it is affected by pathology, as well as current contributions to novel therapeutic approaches will be highlighted.

Nonalcoholic Fatty Liver Disease (NAFLD). Mitochondria as Players and Targets of Therapies?

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and represents the hepatic expression of several metabolic abnormalities of high epidemiologic relevance. Fat accumulation in the hepatocytes results in cellular fragility and risk of progression toward necroinflammation, i.e., nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and eventually hepatocellular carcinoma. Several pathways contribute to fat accumulation and damage in the liver and can also involve the mitochondria, whose functional integrity is essential to maintain liver bioenergetics. In NAFLD/NASH, both structural and functional mitochondrial abnormalities occur and can involve mitochondrial electron transport chain, decreased mitochondrial β-oxidation of free fatty acids, excessive generation of reactive oxygen species, and lipid peroxidation. NASH is a major target of therapy, but there is no established single or combined treatment so far. Notably, translational and clinical studies point to mitochondria as future therapeutic targets in NAFLD since the prevention of mitochondrial damage could improve liver bioenergetics.

The effect of mitochondrial transplantation therapy from different gender on inhibiting cell proliferation of malignant melanoma

Today mitochondria are considered much more than a energy plant in cells. Mitochondrial transplantation therapy has been an active research area for treating mitochondria-associated diseases from animal studies to clinical trials. However, the specific mechanism involved in the anti-tumor activity of healthy mitochondria remain to be characterized. Here we investigate the signal mechanism and gender difference of mitochondrial transplantation therapy against malignant melanoma. In the study, we administrated intact mitochondria extracted from mouse livers respectively to the mice bearing malignantly subcutaneous and metastatic melanoma, and identified the signal mechanism responsible for the mitochondrial treatment through transcriptomic analysis. Meanwhile, the efficiency of female mitochondria and male mitochondria was compared in the cultured melanoma cells and transplanted melanoma in mice. The results suggested that the mitochondria significantly inhibited the tumor cell proliferation in vitro through cell cycle arrest and induction of cell apoptosis. In the melanoma-bearing mice, the mitochondria retard the tumor growth and lung migration, and the transcriptomic analysis indicated that general chromosome silencing was strongly associated with the mitochondria against melanoma after the mitochondrial transplantation on the metastasis melanoma. Moreover, the anti-tumor activity of mitochondria from female animals was more efficient in comparison to the males, and the female mitochondria could probably induce more persuasive mitochondria-nuclear communication than the mitochondria from male mice. The study identifies the anti-tumor mechanism of the mitochondrial transplantation therapy, and provides a novel insight into the effect of mitochondria from different gender.

Mitochondrial Transplantation as a Novel Therapeutic Strategy for Mitochondrial Diseases

Mitochondria are the major source of intercellular bioenergy in the form of ATP. They are necessary for cell survival and play many essential roles such as maintaining calcium homeostasis, body temperature, regulation of metabolism and apoptosis. Mitochondrial dysfunction has been observed in variety of diseases such as cardiovascular disease, aging, type 2 diabetes, cancer and degenerative brain disease. In other words, the interpretation and regulation of mitochondrial signals has the potential to be applied as a treatment for various diseases caused by mitochondrial disorders. In recent years, mitochondrial transplantation has increasingly been a topic of interest as an innovative strategy for the treatment of mitochondrial diseases by augmentation and replacement of mitochondria. In this review, we focus on diseases that are associated with mitochondrial dysfunction and highlight studies related to the rescue of tissue-specific mitochondrial disorders. We firmly believe that mitochondrial transplantation is an optimistic therapeutic approach in finding a potentially valuable treatment for a variety of mitochondrial diseases.