Mitochondria Can Cross Cell Boundaries: An Overview of the Biological Relevance, Pathophysiological Implications and Therapeutic Perspectives of Intercellular Mitochondrial Transfer.

Mitochondria are complex intracellular organelles traditionally identified as the powerhouses of eukaryotic cells due to their central role in bioenergetic metabolism. In recent decades, the growing interest in mitochondria research has revealed that these multifunctional organelles are more than just the cell powerhouses, playing many other key roles as signaling platforms that regulate cell metabolism, proliferation, death and immunological response. As key regulators, mitochondria, when dysfunctional, are involved in the pathogenesis of a wide range of metabolic, neurodegenerative, immune and neoplastic disorders. Far more recently, mitochondria attracted renewed attention from the scientific community for their ability of intercellular translocation that can involve whole mitochondria, mitochondrial genome or other mitochondrial components. The intercellular transport of mitochondria, defined as horizontal mitochondrial transfer, can occur in mammalian cells both in vitro and in vivo, and in physiological and pathological conditions. Mitochondrial transfer can provide an exogenous mitochondrial source, replenishing dysfunctional mitochondria, thereby improving mitochondrial faults or, as in in the case of tumor cells, changing their functional skills and response to chemotherapy. In this review, we will provide an overview of the state of the art of the up-to-date knowledge on intercellular trafficking of mitochondria by discussing its biological relevance, mode and mechanisms underlying the process and its involvement in different pathophysiological contexts, highlighting its therapeutic potential for diseases with mitochondrial dysfunction primarily involved in their pathogenesis.

Recent advances in the immunopathogenesis of severe asthma.

Severe asthma is a heterogeneous disease encompassing different phenotypes and endotypes. Although patients with severe asthma constitute a small proportion of the total population with asthma, they largely account for the morbidity and mortality associated with asthma, indicating a clear unmet need. Being distinct from mild and moderate disease, new insights into the immunopathogenesis of severe asthma are needed. The disease endotypes have provided better insights into the immunopathogenic mechanisms underlying severe asthma. Current stratified approach of treating severe asthma based on phenotypes is met with shortcomings, necessitating unbiased multidimensional endotyping to cope with disease complexity. Therefore, in this review, we explore the distinct endotypes and their mechanistic pathways that characterize the heterogeneity observed in severe asthma.

Neurological Implications of COVID-19: Role of Redox Imbalance and Mitochondrial Dysfunction.

Severe acute respiratory syndrome coronavirus (SARS-CoV)-2 or COVID-19 has been declared as a pandemic disease by the World Health Organization (WHO). Globally, this disease affected 159 million of the population and reported ~ 3.3 million deaths to the current date (May 2021). There is no definitive treatment strategy that has been identified, although this disease has prevailed in its current form for the past 18 months. The main challenges in the (SARS-CoV)-2 infections are in identifying the heterogeneity in viral strains and the plausible mechanisms of viral infection to human tissues. In parallel to the investigations into the patho-mechanism of SARS-CoV-2 infection, understanding the fundamental processes underlying the clinical manifestations of COVID-19 is very crucial for designing effective therapies. Since neurological symptoms are very apparent in COVID-19 infected patients, here, we tried to emphasize the involvement of redox imbalance and subsequent mitochondrial dysfunction in the progression of the COVID-19 infection. It has been articulated that mitochondrial dysfunction is very apparent and also interlinked to neurological symptoms in COVID-19 infection. Overall, this article provides an in-depth overview of redox imbalance and mitochondrial dysfunction involvement in aggravating COVID-19 infection and its probable contribution to the neurological manifestation of the disease.

Potential Therapeutic Applications of Hydrogen in Chronic Inflammatory Diseases: Possible Inhibiting Role on Mitochondrial Stress.

Mitochondria are the largest source of reactive oxygen species (ROS) and are intracellular organelles that produce large amounts of the most potent hydroxyl radical (·OH). Molecular hydrogen (H2) can selectively eliminate ·OH generated inside of the mitochondria. Inflammation is induced by the release of proinflammatory cytokines produced by macrophages and neutrophils. However, an uncontrolled or exaggerated response often occurs, resulting in severe inflammation that can lead to acute or chronic inflammatory diseases. Recent studies have reported that ROS activate NLRP3 inflammasomes, and that this stimulation triggers the production of proinflammatory cytokines. It has been shown in literature that H2 can be based on the mechanisms that inhibit mitochondrial ROS. However, the ability for H2 to inhibit NLRP3 inflammasome activation via mitochondrial oxidation is poorly understood. In this review, we hypothesize a possible mechanism by which H2 inhibits mitochondrial oxidation. Medical applications of H2 may solve the problem of many chronic inflammation-based diseases, including coronavirus disease 2019 (COVID-19).

Synthesis of N,N'-bis(1,5-dimethyl-2-phenyl-1,2-dihydro-3-oxopyrazol-4-yl) sebacamide that ameliorate osteoarthritis symptoms and improve bone marrow matrix structure and cartilage alterations induced by monoiodoacetate in the rat model: "Suggested potent anti-inflammatory agent against COVID-19".

To assess the chondroprotective effect and influence of N,N'-bis(1,5-dimethyl-2-phenyl-1,2-dihydro-3-oxopyrazol-4-yl) sebacamide (dpdo) that was synthesized through the reaction of phenazone with sebacoyl chloride and screened for its biological activity especially as anti-arthritic and anti-inflammatory agent in a monoiodoacetate (MA)-induced experimental osteoarthritis (OA) model. Thirty male albino rats weighing "190-200 g" were divided randomly into three groups (10 each): control, MA-induced OA, and MA-induced OA + dpdo. In MA-induced OA rat, the tumor necrosis factor alpha, interleukin 6, C-reactive protein, rheumatoid factors, reactive oxygen species, as well as all the mitochondrial markers such as mitochondria membrane potential, swelling mitochondria, cytochrome c oxidase (complex IV), and serum oxidative/antioxidant status (malondialdehyde level and activities of myeloperoxidase and xanthine oxidase) are elevated. Also, the activity of succinate dehydrogenase (complex II), levels of ATP, the level of glutathione (GSH), and thiol were markedly diminished in the MA-induced OA group compared to the normal control rats. These findings showed that mitochondrial function is associated with OA pathophysiological alterations and high gene expressions of (IL-6, TNF-a, and IL-1b) and suggests a promising use of dpdo as potential ameliorative agents in the animal model of OA and could act as anti-inflammatory agent in case of severe infection with COVID-19. It is clearly appeared in improving the bone cortex and bone marrow in the treated group with the novel compound in histological and transmission electron microscopic sections which is a very important issue today in fighting severe infections that have significant effects on the blood indices and declining of blood corpuscles like COVID-19, in addition to declining the genotoxicity and inflammation induced by MA in male rats. The novel synthesized compound was highly effective in improving all the above mentioned parameters.

Inflammation-Induced Protein Unfolding in Airway Smooth Muscle Triggers a Homeostatic Response in Mitochondria.

The effects of airway inflammation on airway smooth muscle (ASM) are mediated by pro-inflammatory cytokines such as tumor necrosis factor alpha (TNFα). In this review article, we will provide a unifying hypothesis for a homeostatic response to airway inflammation that mitigates oxidative stress and thereby provides resilience to ASM. Previous studies have shown that acute exposure to TNFα increases ASM force generation in response to muscarinic stimulation (hyper-reactivity) resulting in increased ATP consumption and increased tension cost. To meet this increased energetic demand, mitochondrial O2 consumption and oxidative phosphorylation increases but at the cost of increased reactive oxygen species (ROS) production (oxidative stress). TNFα-induced oxidative stress results in the accumulation of unfolded proteins in the endoplasmic reticulum (ER) and mitochondria of ASM. In the ER, TNFα selectively phosphorylates inositol-requiring enzyme 1 alpha (pIRE1α) triggering downstream splicing of the transcription factor X-box binding protein 1 (XBP1s); thus, activating the pIRE1α/XBP1s ER stress pathway. Protein unfolding in mitochondria also triggers an unfolded protein response (mtUPR). In our conceptual framework, we hypothesize that activation of these pathways is homeostatically directed towards mitochondrial remodeling via an increase in peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC1α) expression, which in turn triggers: (1) mitochondrial fragmentation (increased dynamin-related protein-1 (Drp1) and reduced mitofusin-2 (Mfn2) expression) and mitophagy (activation of the Phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1)/Parkin mitophagy pathway) to improve mitochondrial quality; (2) reduced Mfn2 also results in a disruption of mitochondrial tethering to the ER and reduced mitochondrial Ca2+ influx; and (3) mitochondrial biogenesis and increased mitochondrial volume density. The homeostatic remodeling of mitochondria results in more efficient O2 consumption and oxidative phosphorylation and reduced ROS formation by individual mitochondrion, while still meeting the increased ATP demand. Thus, the energetic load of hyper-reactivity is shared across the mitochondrial pool within ASM cells.

Age-related mitochondrial dysfunction as a key factor in COVID-19 disease.

SARS-CoV-2 causes a severe pneumonia (COVID-19) that affects essentially elderly people. In COVID-19, macrophage infiltration into the lung causes a rapid and intense cytokine storm leading finally to a multi-organ failure and death. Comorbidities such as metabolic syndrome, obesity, type 2 diabetes, lung and cardiovascular diseases, all of them age-associated diseases, increase the severity and lethality of COVID-19. Mitochondrial dysfunction is one of the hallmarks of aging and COVID-19 risk factors. Dysfunctional mitochondria is associated with defective immunological response to viral infections and chronic inflammation. This review discuss how mitochondrial dysfunction is associated with defective immune response in aging and different age-related diseases, and with many of the comorbidities associated with poor prognosis in the progression of COVID-19. We suggest here that chronic inflammation caused by mitochondrial dysfunction is responsible of the explosive release of inflammatory cytokines causing severe pneumonia, multi-organ failure and finally death in COVID-19 patients. Preventive treatments based on therapies improving mitochondrial turnover, dynamics and activity would be essential to protect against COVID-19 severity.

Trauma of major surgery: A global problem that is not going away.

Globally, a staggering 310 million major surgeries are performed each year; around 40 to 50 million in USA and 20 million in Europe. It is estimated that 1-4% of these patients will die, up to 15% will have serious postoperative morbidity, and 5-15% will be readmitted within 30 days. An annual global mortality of around 8 million patients places major surgery comparable with the leading causes of death from cardiovascular disease and stroke, cancer and injury. If surgical complications were classified as a pandemic, like HIV/AIDS or coronavirus (COVID-19), developed countries would work together and devise an immediate action plan and allocate resources to address it. Seeking to reduce preventable deaths and post-surgical complications would save billions of dollars in healthcare costs. Part of the global problem resides in differences in institutional practice patterns in high- and low-income countries, and part from a lack of effective perioperative drug therapies to protect the patient from surgical stress. We briefly review the history of surgical stress and provide a path forward from a systems-based approach. Key to progress is recognizing that the anesthetized brain is still physiologically 'awake' and responsive to the sterile stressors of surgery. New intravenous drug therapies are urgently required after anesthesia and before the first incision to prevent the brain from switching to sympathetic overdrive and activating secondary injury progression such as hyperinflammation, coagulopathy, immune activation and metabolic dysfunction. A systems-based approach targeting central nervous system-mitochondrial coupling may help drive research to improve outcomes following major surgery in civilian and military medicine.

The Role of Genetic Sex and Mitochondria in Response to COVID-19 Infection.

The difference between the female and male immune response to COVID-19 infection, and infections in general, is multifactorial. The well-known determiners of the immune response, such as X and Y chromosomes, sex hormones, and microbiota, are functionally interconnected and influence each other in shaping the organism's immunity. We focus our commentary on the interplay between the genetic sex and mitochondria and how this may affect a sex-dependent immune response in COVID-19 infection. Realizing the existence of these interactions may help in designing novel methods or fine-tuning the existing and routine therapies to fight COVID-19 and other infections.

Novel insights on the pulmonary vascular consequences of COVID-19.

In the last few months, the number of cases of a new coronavirus-related disease (COVID-19) rose exponentially, reaching the status of a pandemic. Interestingly, early imaging studies documented that pulmonary vascular thickening was specifically associated with COVID-19 pneumonia, implying a potential tropism of the virus for the pulmonary vasculature. Moreover, SARS-CoV-2 infection is associated with inflammation, hypoxia, oxidative stress, mitochondrial dysfunction, DNA damage, and lung coagulopathy promoting endothelial dysfunction and microthrombosis. These features are strikingly similar to what is seen in pulmonary vascular diseases. Although the consequences of COVID-19 on the pulmonary circulation remain to be explored, several viruses have been previously thought to be involved in the development of pulmonary vascular diseases. Patients with preexisting pulmonary vascular diseases also appear at increased risk of morbidity and mortality. The present article reviews the molecular factors shared by coronavirus infection and pulmonary vasculature defects, and the clinical relevance of pulmonary vascular alterations in the context of COVID-19.

Iron: Innocent bystander or vicious culprit in COVID-19 pathogenesis?

The coronavirus 2 (SARS-CoV-2) pandemic is viciously spreading through the continents with rapidly increasing mortality rates. Current management of COVID-19 is based on the premise that respiratory failure is the leading cause of mortality. However, mounting evidence links accelerated pathogenesis in gravely ill COVID-19 patients to a hyper-inflammatory state involving a cytokine storm. Several components of the heightened inflammatory state were addressed as therapeutic targets. Another key component of the heightened inflammatory state is hyper-ferritinemia which reportedly identifies patients with increased mortality risk. In spite of its strong association with mortality, it is not yet clear if hyper-ferritinemia in COVID-19 patients is merely a systemic marker of disease progression, or a key modulator in disease pathogenesis. Here we address implications of a possible role for hyper-ferritinemia, and altered iron homeostasis in COVID-19 pathogenesis, and potential therapeutic targets in this regard.