Laboratory of structure and functions of mitochondria

Ischemic diseases represent a broad and complex group of clinical pathologies caused by acute or chronic tissue perfusion disorders [...].

Being among the most metabolically active organs, brain and kidneys critically depend on efficient energy metabolism, which primarily relies on oxidative phosphorylation. Acute pathological conditions associated with a lack of metabolic substrates or their impaired utilization trigger signaling cascades that initiate cell death and lead to poorly reversible organ dysfunction. One of the therapeutic approaches to correct the energy deficit is administration of exogenous metabolites of the tricarboxylic acid cycle, such as succinate. In this study, we investigated the effects of exogenous succinate on astrocytes and renal epithelial cells under normal conditions and in serum deprivation-induced injury. Incubation with succinate increased the viability of both cell types under normal and pathological conditions, but a more pronounced cytoprotective effect was observed in renal cells. In injured renal epithelial cells, succinate increased mitochondrial membrane potential, a critical parameter for the maintenance of mitochondrial function and ATP generation. Comparison of respiration and oxidative phosphorylation parameters in astrocytes and renal epithelial cells in the presence of exogenous succinate revealed that epithelial cells exhibited a significantly higher respiratory control and lower proton leak compared to astrocytes, which correlated with the higher cytoprotective activity of succinate for kidney cells. Therefore, succinate showed a noticeable positive effect in the renal epithelium both under normal conditions and after serum deprivation; however, in astrocytes, its effect was less pronounced. This discrepancy might be related to a more efficient succinate utilization by the mitochondria in renal cells and intrinsic bioenergetic differences between astrocytes and epithelial cells. Despite the clinical use of succinate-containing drugs, the determination of optimal dosages and development of effective therapeutic regimens require further investigation. Our results demonstrate cell type-dependent differences in the efficacy of succinate, suggesting that its therapeutic potential may differ significantly depending on the organ-specific bioenergetic and metabolic properties.

Obstructive nephropathy is a common clinical condition caused by urinary retention. After urine flow is restored, kidney function is recovered. However, the effectiveness of this process can be influenced by many factors, including the age of the patient. In this study, we analyzed the following parameters in young and old rats subjected to a 3-day reversible unilateral ureteral obstruction (R-UUO): AKI severity, renal tissue proliferation and histology, inflammatory and fibrosis marker expression, as well as autophagosomal-lysosomal and mitochondrial function. Compared to old rats, young animals exhibited more pronounced renal tissue proliferation and higher expression of profibrotic markers (<i>Col1a1</i>, <i>Fn1</i>, <i>Tgfb1</i>, <i>MMP2</i>), but diminished expression of pro-inflammatory markers (<i>Il1b</i>, <i>Tnfa</i>, <i>Cd32</i>) in response to R-UUO. Additionally, young rats showed more pronounced activity of autophagy, as indicated by increased beclin-1 levels. R-UUO induced severe damage to the mitochondrial respiratory chain in old animals, as indicated by reduced complex I, IV, cytochrome c, VDAC protein levels, and impaired mitochondrial biogenesis (associated with decreased <i>Pgc1a</i> mRNA expression). Thus, we demonstrated that despite restored urine outflow, kidneys exhibited autophagy activation, inflammatory response, and mitochondrial dysfunction after R-UUO. Negative alterations in the kidney were age-dependent indicating necessity for therapeutic strategies optimization for patients of different ages.

Ischemia-reperfusion (I/R) injury is a complex pathological process underlying numerous acute organ failures and is a significant cause of morbidity and mortality in diseases such as myocardial infarction, stroke, thrombosis, and organ transplantation. Mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) have demonstrated considerable therapeutic potential, but their broad tropism and general repair signaling may limit their efficacy. This review addresses the emerging paradigm of using organ-specific EVs for the treatment of I/R injury in the respective organs. We summarize the existing studies performed on experimental animals showing that these native EVs could possess tissue tropism and carry a specialized cargo of proteins, miRNAs, and lipids tailored to the unique regenerative needs of their organ of origin, enabling them to precisely modulate key processes, including inflammation, apoptosis, oxidative stress, and angiogenesis. However, their clinical translation faces challenges related to scalable production, standardization, and the dualistic nature of their effects, which can be either protective or detrimental, depending on the cellular source and pathophysiological context. Future developments need to focus on overcoming these obstacles through rigorous isolation protocols, engineering strategies such as cargo enrichment and hybrid vesicle creation, and validation in large-animal models. Overall, organ-specific EVs offer a novel, cell-free therapeutic strategy with the potential to significantly improve outcomes in I/R injury.

No abstract

We studied the effects of glucose and glutamine deficiency on the survival of astrocytes after ischemic injury and examined the mechanisms of cell death. It was found that glutamine can serve as an alternative energy substrate that maintains oxidative phosphorylation and glycolysis in astrocytes. However, the combination of glucose and glutamine reduced the ischemia-induced increase in intracellular calcium and the expression of proapoptotic proteins to a greater extent. The results of the study indicate the possibility of using glutamine to maintain the viability of brain cells under conditions of oxygen and energy substrate deprivation.

Renocardiac syndrome type 4 (RCS4) is a common comorbid pathology, but the mechanisms of kidney dysfunction-induced cardiac remodeling and the involvement of cardiac progenitor cells (CPCs) in this process remain unclear. The aim of this study was to investigate the structural and functional changes in the cardiac muscle in RCS4 induced by unilateral ureteral obstruction (UUO) and the role of nestin⁺ CPCs in these. Heart function and localization of nestin⁺ cells in the myocardium were assessed using nestin-GFP transgenic mice subjected to UUO for 14 and 28 days. UUO resulted in cardiac hypertrophy, accompanied by an elongation of the QRS wave on the ECG, decreased expression of <i>Cxcl1</i>, <i>Cxcl9</i>, and <i>Il1b</i>, reduced the number of CD11b⁺ cells, and increased in titin isoform parameters, such as T1/MHC and TT/MHC ratios, without changes in fibrosis markers. The number of nestin⁺ cells increased in the myocardium with increased duration of UUO and displayed an SCA-1⁺TBX5⁺ phenotype, consistent with CPCs. Thus, cardiac pathology in RCS4 was manifested by cardiomyocyte hypertrophy with changes in the electrophysiological phenotype of the heart, not accompanied by fibrosis or inflammation. Nestin⁺ cardiac cells retained the CPC phenotype during UUO, and their number increased, which suggests their participation in regenerative processes in the heart.

Undesirable tissue fibroblast activation after injury is still an unresolved problem for many organs, including the kidney. Kidney fibroblasts and tubular epithelial cells demonstrate significant differences in gene expression profiles, including metabolism-related genes. As a result, these cell types exhibit differences in the energy metabolism that could be the basis of targeted therapy for fibrosis. Among other deacetylase inhibition is considered a therapeutic approach that could simultaneously promote tissue regeneration and suppress the development of fibrosis, but their relation to bioenergetics has not been considered before. In this study, we aimed to compare the influence of the HDAC inhibitor trichostatin A (TSA) on renal tubular epithelial cells and kidney fibroblasts. We analyzed resemblance and differences in TSA effects on the proliferative activity of the cells and investigated the molecular mechanisms responsible for these effects; e.g., we focused on the activity of signaling pathways associated with cell viability (Akt/mTOR/p70^S6). We found that TSA increased the proliferation rate of epithelial cells, while it tended to decrease the growth rate of fibroblasts. Furthermore, the amount of phosphorylated forms of kinases Akt and P70^S6 increased in epithelial cells after incubation with TSA, indicating the activation of the Akt/mTOR/p70^S6 signaling pathway, while decreasing its activity in fibroblast cells. Since there are differences in the bioenergetics between fibroblasts and epithelial cells, we investigated the impact of TSA on the glycolytic activity of both cell types. Indeed, we showed that TSA reduced the activity of glycolytic processes in fibroblast cells. The observed changes indicate a positive effect of TSA on regenerative versus fibrotic processes in the kidney by reducing the growth and metabolic activity of fibroblasts and activating the proliferation of epithelial cells.

The levels of inflammatory markers increased in both mouse blood plasma and affected brain area 24 days after traumatic brain injury, which was accompanied by impairment of spatial working memory. Methylene blue administered during the first 3 days after injury reduced the levels of some inflammation markers and increased the expression of genes involved in the regulation of mitochondrial biogenesis and mitophagy, i.e. genes responsible for mitochondrial quality control. Additionally, methylene blue partially mitigated the cognitive deficits induced by the injury, suggesting it as a promising compound for maintaining brain function after traumas.