Methane Admixture Protects Liver Mitochondria and Improves Graft Function after Static Cold Storage and Reperfusion.

Mitochondria are targets of cold ischemia-reperfusion (IR), the major cause of cell damage during static cold preservation of liver allografts. The bioactivity of methane (CH4) has recently been recognized in various hypoxic and IR conditions as having influence on many aspects of mitochondrial biology. We therefore hypothesized that cold storage of liver grafts in CH4-enriched preservation solution can provide an increased defence against organ dysfunction in a preclinical rat model of liver transplantation. Livers were preserved for 24 h in cold histidine-tryptophan-ketoglutarate (HTK) or CH4-enriched HTK solution (HTK-CH4) (n = 24 each); then, viability parameters were monitored for 60 min during normothermic isolated reperfusion and perfusate and liver tissue were collected. The oxidative phosphorylation capacity and extramitochondrial Ca2+ movement were measured by high resolution respirometry. Oxygen and glucose consumption increased significantly while hepatocellular damage was decreased in the HTK-CH4 grafts compared to the HTK group. Mitochondrial oxidative phosphorylation capacity was more preserved (128.8 ± 31.5 pmol/s/mL vs 201.3 ± 54.8 pmol/s/mL) and a significantly higher Ca2+ flux was detected in HTK-CH4 storage (2.9 ± 0.1 mV/s) compared to HTK (2.3 ± 0.09 mV/s). These results demonstrate the direct effect of CH4 on hepatic mitochondrial function and extramitochondrial Ca2+ fluxes, which may have contributed to improved graft functions and a preserved histomorphology after cold IR.

Mitochondrial Dysfunction Affects the Synovium of Patients with Rheumatoid Arthritis and Osteoarthritis Differently.

There is growing evidence regarding the role of mitochondrial dysfunction in osteoarthritis (OA) and rheumatoid arthritis (RA). However, quantitative comparison of synovial mitochondrial derangements in these main arthritis forms is missing. A prospective clinical study was conducted on adult patients undergoing knee surgery. Patients were allocated into RA and OA groups based on disease-specific clinical scores, while patients without arthritis served as controls. Synovial samples were subjected to high-resolution respirometry to analyze mitochondrial functions. From the total of 814 patients, 109 cases were enrolled into the study (24 RA, 47 OA, and 38 control patients) between 1 September 2019 and 31 December 2021. The decrease in complex I-linked respiration and dyscoupling of mitochondria were characteristics of RA patients, while both arthritis groups displayed reduced OxPhos activity compared to the control group. However, no significant difference was found in complex II-related activity between the OA and RA groups. The cytochrome C release and H2O2 formation were increased in both arthritis groups. Mitochondrial dysfunction was present in both arthritis groups; however, to a different extent. Consequently, mitochondrial protective agents may have major benefits for arthritis patients. Based on our current study, we recommend focusing on respiratory complex I in rheumatoid arthritis research.

Mitochondrial Side Effects of Surgical Prophylactic Antibiotics Ceftriaxone and Rifaximin Lead to Bowel Mucosal Damage.

Despite their clinical effectiveness, a growing body of evidence has shown that many classes of antibiotics lead to mitochondrial dysfunction. Ceftriaxone and Rifaximin are first choice perioperative antibiotics in gastrointestinal surgery targeting fundamental processes of intestinal bacteria; however, may also have negative consequences for the host cells. In this study, we investigated their direct effect on mitochondrial functions in vitro, together with their impact on ileum, colon and liver tissue. Additionally, their impact on the gastrointestinal microbiome was studied in vivo, in a rat model. Rifaximin significantly impaired the oxidative phosphorylation capacity (OxPhos) and leak respiration in the ileal mucosa, in line with increased oxidative tissue damage and histological changes following treatment. Ceftriaxone prophylaxis led to similar changes in the colon mucosa. The composition and diversity of bacterial communities differed extensively in response to antibiotic pre-treatment. However, the relative abundances of the toxin producing species were not increased. We have confirmed the harmful effects of prophylactic doses of Rifaximin and Ceftriaxone on the intestinal mucosa and that these effects were related to the mitochondrial dysfunction. These experiments raise awareness of mitochondrial side effects of these antibiotics that may be of clinical importance when evaluating their adverse effects on bowel mucosa.

Reduction in hypoxia-reoxygenation-induced myocardial mitochondrial damage with exogenous methane.

Albeit previous experiments suggest potential anti-inflammatory effect of exogenous methane (CH4 ) in various organs, the mechanism of its bioactivity is not entirely understood. We aimed to investigate the potential mitochondrial effects and the underlying mechanisms of CH4 in rat cardiomyocytes and mitochondria under simulated ischaemia/reperfusion (sI/R) conditions. Three-day-old cultured cardiomyocytes were treated with 2.2% CH4 -artificial air mixture during 2-hour-long reoxygenation following 4-hour-long anoxia (sI/R and sI/R + CH4 , n = 6-6), with normoxic groups serving as controls (SH and SH + CH4 ; n = 6-6). Mitochondrial functions were investigated with high-resolution respirometry, and mitochondrial membrane injury was detected by cytochrome c release and apoptotic characteristics by using TUNEL staining. CH4 admixture had no effect on complex II (CII)-linked respiration under normoxia but significantly decreased the complex I (CI)-linked oxygen consumption. Nevertheless, addition of CH4 in the sI/R + CH4 group significantly reduced the respiratory activity of CII in contrast to CI and the CH4 treatment diminished mitochondrial H2 O2 production. Substrate-induced changes to membrane potential were partially preserved by CH4 , and additionally, cytochrome c release and apoptosis of cardiomyocytes were reduced in the CH4 -treated group. In conclusion, the addition of CH4 decreases mitochondrial ROS generation via blockade of electron transport at CI and reduces anoxia-reoxygenation-induced mitochondrial dysfunction and cardiomyocyte injury in vitro.

Mitochondrial Consequences of Organ Preservation Techniques during Liver Transplantation.

Allograft ischemia during liver transplantation (LT) adversely affects the function of mitochondria, resulting in impairment of oxidative phosphorylation and compromised post-transplant recovery of the affected organ. Several preservation methods have been developed to improve donor organ quality; however, their effects on mitochondrial functions have not yet been compared. This study aimed to summarize the available data on mitochondrial effects of graft preservation methods in preclinical models of LT. Furthermore, a network meta-analysis was conducted to determine if any of these treatments provide a superior benefit, suggesting that they might be used on humans. A systematic search was conducted using electronic databases (EMBASE, MEDLINE (via PubMed), the Cochrane Central Register of Controlled Trials (CENTRAL) and Web of Science) for controlled animal studies using preservation methods for LT. The ATP content of the graft was the primary outcome, as this is an indicator overall mitochondrial function. Secondary outcomes were the respiratory activity of mitochondrial complexes, cytochrome c and aspartate aminotransferase (ALT) release. Both a random-effects model and the SYRCLE risk of bias analysis for animal studies were used. After a comprehensive search of the databases, 25 studies were enrolled in the analysis. Treatments that had the most significant protective effect on ATP content included hypothermic and subnormothermic machine perfusion (HMP and SNMP) (MD = -1.0, 95% CI: (-2.3, 0.3) and MD = -1.1, 95% CI: (-3.2, 1.02)), while the effects of warm ischemia (WI) without cold storage (WI) and normothermic machine perfusion (NMP) were less pronounced (MD = -1.8, 95% CI: (-2.9, -0.7) and MD = -2.1 MD; CI: (-4.6; 0.4)). The subgroup of static cold storage (SCS) with shorter preservation time (< 12 h) yielded better results than SCS ≥ 12 h, NMP and WI, in terms of ATP preservation and the respiratory capacity of complexes. HMP and SNMP stand out in terms of mitochondrial protection when compared to other treatments for LT in animals. The shorter storage time at lower temperatures, together with the dynamic preservation, provided superior protection for the grafts in terms of mitochondrial function. Additional clinical studies on human patients including marginal donors and longer ischemia times are needed to confirm any superiority of preservation methods with respect to mitochondrial function.

Methane supplementation improves graft function in experimental heart transplantation.

BACKGROUND: Maintenance of cell viability during cold storage is a key issue in organ transplantation. Methane (CH4) bioactivity has recently been recognized in ischemia/reperfusion conditions; we therefore hypothesized that cold storage in CH4-enriched preservation solution can provide an increased defense against organ dysfunction during experimental heart transplantation (HTX). METHODS: The hearts of donor Lewis rats were stored for 60 minutes in cold histidine-tryptophan-ketoglutarate (Custodiol [CS]) or CH4-saturated CS solution (CS-CH4) (n = 12 each). Standard heterotopic HTX was performed, and 60 minutes later, the left ventricular (LV) pressure-volume relationships LV systolic pressure (LVSP), systolic pressure increment (dP/dtmax), diastolic pressure decrement, and coronary blood flow (CBF) were measured. Tissue samples were taken to detect proinflammatory parameters, structural damage (by light microscopy), endoplasmic reticulum (ER) stress, and apoptosis markers (CCAAT/enhancer binding protein [C/EBP] homologous protein, GRP78, glycogen synthase kinase-3ß, very low-density lipoprotein receptor, caspase 3 and 9, B-cell lymphoma 2, and bcl-2-like protein 4), whereas mitochondrial functional changes were analyzed by high-resolution respirometry. RESULTS: LVSP and dP/dtmax increased significantly at the largest pre-load volumes in CS-CH4 grafts as compared with the CS group (114.5 ± 16.6 mm Hg vs 82.8 ± 4.6 mm Hg and 3,133 ± 430 mm Hg/s vs 1,739 ± 169 mm Hg/s, respectively); the diastolic function and CBF (2.4 ± 0.4 ml/min/g vs 1.3 ± 0.3 ml/min/g) also improved. Mitochondrial oxidative phosphorylation capacity was more preserved (58.5 ± 9.4 pmol/s/ml vs 27.7 ± 6.6 pmol/s/ml), and cytochrome c release was reduced in CS-CH4 storage. Signs of HTX-caused myocardial damage, level of ER stress, and the transcription of proapoptotic proteins were significantly lower in CS-CH4 grafts. CONCLUSION: The addition of CH4 during 1 hour of cold storage improved early in vitro graft function and reduced mitochondrial dysfunction and activation of inflammation. Evidence shows that CH4 reduced ER stress-linked proapoptotic signaling.

[Examination of liver mitochondria with respirometry]. / A májfunkció vizsgálata respirometriával.

Due to their diverse physiological functions, mitochondria can cause various acute and chronic liver diseases, thus being potential targets for therapies and diagnostics as well. In this study, the advantages of high-resolution respirometry are presented for the assessment of liver mitochondrial functions. During respitometry, the mitochondrial electron transport, the oxydative phosphorilation and the efficacy of the ADP synthesis can be calculated on the basis of oxygen consumption of freshly-taken tissue samples. Respirometry is a robust tool for the pre- or intraoperative analysis of liver mitochondrial functions and may increase the effectiveness of surgical interventions.