Search

Abstract: Background: Fatty livers are considerably more susceptible to acute stressors, such as ischaemia/reperfusion (I/R). As the incidence of I/R is high due to surgical events and some pathologies, there is an urgent need to find strategies against I/R injury (I/RI) in fatty livers. We postulate that an acute pretreatment with indirubin‐3′‐oxime (Ind) or NAD+ prevents mitochondrial dysfunction associated with warm I/RI in fatty livers. Materials and Methods: Zucker fatty rats were subjected to warm ischaemia and 12 hours of reperfusion. Ind or NAD+ was administered in the hepatic artery 30 minutes before ischaemia. Hepatic mitochondrial isolation was performed, and functional assays as well as molecular analysis were performed. Results: Pretreatment decreased markers of liver injury while preserving mitochondrial cytochrome c content, which is related to the prevention of calcium‐induced mitochondrial permeability transition (mPT), the decline in mitochondrial respiratory state 3 and ATP content. The generation of reactive oxygen species (ROS) was also diminished. Inhibition of GSK‐3ß by Ind resulted in the prevention of cyclophilin‐D (CypD) phosphorylation, unabling it to bind to the adenine nucleotide translocator (ANT), thus, preventing mPT induction. Furthermore, deacetylation of CypD at Lys residue by sirtuin 3 (SIRT3) caused its dissociation from ANT, contributing to an increase in mPT threshold in NAD+‐pretreated animals. Conclusions: Pretreatment with Ind or NAD+ protects fatty livers by maintaining mitochondrial calcium homoeostasis, thus, preserving mitochondrial function and energetic balance. As such, CypD might be a new protective target against I/RI in fatty livers. [ABSTRACT FROM AUTHOR]

Background Liver regeneration requires an enormous energy supply. Experimental evidence suggests that mitochondrial function is of paramount importance for liver regeneration. However, this has not been investigated in the clinical setting. We aimed to: (i) evaluate changes in mitochondrial function during hepatectomy, especially after hepatic pedicle clamping; and (ii) correlate these changes with postoperative hepatocellular function and clinical outcome. Materials and methods Prospective study of thirty patients undergoing hepatectomy. Measurement of mitochondrial membrane potential, respiration and adenosine triphosphate content in intra-operative liver biopsies performed in nonresected parenchyma. Correlation of findings with duration of hepatic pedicle clamping, postoperative markers of hepatocellular necrosis and function (aminotransferases, arterial lactate, international normalized ratio, bilirubin), and morbidity. Results Longer hepatic pedicle clamping was associated with worse mitochondrial depolarization ( r = −0·519; P = 0·011) and longer lag phase ( r = 0·568; P = 0·006). Higher postoperative peak aminotransferases, international normalized ratio and bilirubin correlated with worse mitochondrial function ( P < 0·05). After major hepatectomy, mitochondrial respiration correlated with postoperative arterial lactate clearance ( r = 0·756; P = 0·049). Mitochondrial bioenergetic parameters were significantly decreased in patients with liver-specific morbidity and postoperative liver failure ( P < 0·05). On multivariate analysis, decrease in mitochondrial potential was an independent risk factor for liver-specific morbidity (OR = 13·7; P = 0·043). Worse lag phase was highly predictive of posthepatectomy liver failure (area under the curve: 0·933; P = 0·008). Conclusions There is a relationship between mitochondrial function, duration of hepatic pedicle clamping and clinical outcome after hepatectomy. Mitochondrial bioenergetics can potentially translate into clinical practice, assisting in earlier diagnosis of postoperative liver dysfunction, and as a target for future pharmacological therapies. [ABSTRACT FROM AUTHOR]

Mitoxantrone (MTX) is a chemotherapeutic agent that emerged as an alternative to anthracycline therapy. However, MTX also causes late cardiotoxicity, being oxidative stress and mitochondrial-impaired function proposed as possible mechanisms. This work aimed to investigate the relevance of these mechanisms to the MTX toxicity in H9c2 cells, using therapeutic concentrations. The observed cytotoxicity of MTX was time and concentration dependent in both lactate dehydrogenase leakage assay and MTT reduction assay. Two therapeutic concentrations (100 nM and 1 μM) and three time points were selected (24, 48, and 96 h) for further studies. Both MTX concentrations caused a significant increase in caspase-3 activity, which was not prevented by inhibiting MTX CYP450-metabolism. Significant decreases were observed in the total and reduced glutathione levels only in MTX 100 nM at 96 h; however, neither alterations in oxidized glutathione nor increases in the malondialdehyde levels were observed at any time or concentrations tested. On the other hand, changes in the intracellular ATP levels, mitochondrial membrane potential, and intracellular calcium levels were observed in both concentrations and all time tested. Noteworthy, decreased levels of ATP-synthase expression and activity and increases in the reactive species generation were observed at 96 h in both working concentrations. However, the radical scavenger N-acetylcysteine or the mitochondrial function enhancer L-carnitine did not prevent MTX cytotoxicity. Thus, this work evidenced the early MTX-induced energetic crisis as a possible key factor in the cell injury. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, we evaluated the potential toxic effects of nerolidol, a sesquiterpenoid common in plants essential oils, both on mitochondrial and cellular energetics. Samples of enriched natural extracts of nerolidol (a racemic mixture of cis and trans isomers) were tested on rat liver mitochondria and a decrease in phosphorylative system was observed but not in the mitochondrial respiratory chain activity, which reflects a direct effect on F1-ATPase. Hence, respiratory control ratio was also decreased. Cellular ATP/ADP levels were significantly decreased in a concentration-dependent manner, possibly due to the direct effect of nerolidol on F0F1-ATPsynthase. Nerolidol stimulates respiratory activity probably due to an unspecific effect, since it does not show any protonophoric effect. Furthermore, we observed that mitochondrial permeability transition was delayed in the presence of nerolidol, possibly due to its antioxidant activity and because this compound decreases mitochondrial transmembrane electric potential. Our results also show that, in human hepatocellular liver carcinoma cell line (HepG2), nerolidol both induces cell death and arrests cell growth, probably related with the observed lower bioenergetic efficiency. [Copyright &y& Elsevier]

Environmental pollutants such as TCDD and tetraethyl lead are extremely toxic and related with pulmonary disease development. Lung mitochondria are primary cellular targets for dioxins exposure-induced toxicity. TCDD showed a delay in the repolarization after a phosphorylative cycle and a decrease on state 3 respiration, suggesting alterations at the phosphorylative system level. The ATPase activity showed no differences between control and lung mitochondria incubated with TCDD, implying alterations in other components of the phosphorylative system. Tetraethyl lead also showed a delay in the repolarization after a phosphorylative cycle and a decrease on RCR. These data suggest that lung mitochondria incubated with TCDD and tetraethyl lead showed impaired mitochondrial function, reflecting the loss of oxidative phosphorylation capacity. [ABSTRACT FROM AUTHOR]

Ischemia/reperfusion (I/R) injury is a commonly encountered clinical problem and occurs probably as a consequence of irreversible mitochondrial injury. The increased susceptibility of fatty livers to ischemic injury is associated with depletion of adenosine triphosphate (ATP) content, which is preserved by preconditioning. Mitochondria being the main ATP production source for the cell, we aimed to evaluate whether ischemic preconditioning (IPC) of fatty livers prevents the impairment in mitochondrial function induced by I/R. Lean and steatotic animals were subjected to 90 min of hepatic warm ischemia and 12 h of reperfusion. IPC effect was tested in fatty livers. After reperfusion, serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were measured. Mitochondrial membrane potential, mitochondrial respiration and susceptibility to mitochondrial permeability transition (MPT) were evaluated, as well as ATPase activity and adenine nucleotides. IPC of fatty livers decreased serum AST and ALT levels. Fatty animals subjected to I/R exhibited decreased mitochondrial membrane potential and a delay in the repolarization after a phosphorylation cycle, associated with increased state 4 respiration. Increased tolerance to MPT induction, preservation of F1Fo-ATPsynthase activity and mitochondrial bioenergetics were observed in ischemic preconditioned fatty livers. Thus, IPC is an endogenous protecting mechanism that preserves mitochondrial function and bioenergetics in fatty livers. [ABSTRACT FROM AUTHOR]

Abstract: Increased generation of reactive oxygen species (ROS) is implicated in “glucose toxicity” in diabetes. However, little is known about the action of glucose on the expression of transcription factors in hepatocytes, especially those involved in mitochondrial DNA (mtDNA) replication and transcription. Since mitochondrial functional capacity is dynamically regulated, we hypothesized that stressful conditions of hyperglycemia induce adaptations in the transcriptional control of cellular energy metabolism, including inhibition of mitochondrial biogenesis and oxidative metabolism. Cell viability, mitochondrial respiration, ROS generation and oxidized proteins were determined in HepG2 cells cultured in the presence of either 5.5 mM (control) or 30 mM glucose (high glucose) for 48 h, 96 h and 7 days. Additionally, mtDNA abundance, plasminogen activator inhibitor-1 (PAI-1), mitochondrial transcription factor A (TFAM) and nuclear respiratory factor-1 (NRF-1) transcripts were evaluated by real time PCR. High glucose induced a progressive increase in ROS generation and accumulation of oxidized proteins, with no changes in cell viability. Increased expression of PAI-1 was observed as early as 96 h of exposure to high glucose. After 7 days in hyperglycemia, HepG2 cells exhibited inhibited uncoupled respiration and decreased MitoTracker Red fluorescence associated with a 25% decrease in mtDNA and 16% decrease in TFAM transcripts. These results indicate that glucose may regulate mtDNA copy number by modulating the transcriptional activity of TFAM in response to hyperglycemia-induced ROS production. The decrease of mtDNA content and inhibition of mitochondrial function may be pathogenic hallmarks in the altered metabolic status associated with diabetes. [Copyright &y& Elsevier]

It has been pointed out that intracellular accumulation of bile acids cause hepatocyte injury in cholestatic disease process. This study was aimed to test if cytotoxicity of these compounds is mediated through mitochondria dysfunction. Bile acids effects on isolated rat liver mitochondrial were analyzed by monitoring changes in membrane potential and mitochondrial respiration, as well as alterations in H+ membrane permeability and mitochondrial permeability transition pore induction. Increasing concentrations of the bile acids litocholic (LCA), deoxycholic (DCA), ursodeoxycholic (UDCA), chenodeoxycholic (CDCA), glycochenodeoxycholic (GCDC), or taurochenodeoxycholic (TCDC) decrease transmembrane potential (ΔΨ) developed upon succinate energization. These compounds also decreased state 3 respiration and enhanced state 4. We have also demonstrated that the observed concentration-dependent stimulation of state 4 by LCA, DCA, CDCA, TCDC, and GCDC, is associated with an enhanced permeability of mitochondria to H+. Addition of LCA, DCA, CDCA, TCDC, GCDC, and UDCA to mitochondria energized with succinate resulted in a dose-dependent membrane depolarization and stimulation of mitochondrial permeability transition. Tauroursodeoxycholate (TUDC) elicited no significant effect on succinate-supported mitochondrial bioenergetics. In contrast, in the presence of glycoursodeoxycholic (GUDC), ΔΨ increases as a function of bile salt concentration. The results of this investigation demonstrate that at toxicologically relevant concentrations, most but not all bile acids alter mitochondrial bioenergetics, so impairment of mitochondrial function can be clinically relevant for patients with cholestasis. [ABSTRACT FROM PUBLISHER]

An emergent trend of blueberries' (BB) "prophylactic" consumption, due to their phytochemicals' richness and well-known health-promoting claims, is widely scaled-up. However, the benefits arising from BB indiscriminate intake remains puzzling based on incongruent preclinical and human data. To provide a more in-depth elucidation and support towards a healthier and safer consumption, we conducted a translation-minded experimental study in healthy Wistar rats that consumed BB in a juice form (25 g/kg body weight (BW)/day; 14 weeks' protocol). Particular attention was paid to the physiological adaptations succeeding in the gut and liver tissues regarding the acknowledged BB-induced metabolic benefits. Systemically, BB boosted serum antioxidant activity and repressed the circulating levels of 3-hydroxybutyrate (3-HB) ketone bodies and 3-HB/acetoacetate ratio. Moreover, BB elicited increased fecal succinic acid levels without major changes on gut microbiota (GM) composition and gut ultra-structural organization. Remarkably, an accentuated hepatic mitochondrial bioenergetic challenge, ensuing metabolic transcriptomic reprogramming along with a concerted anti-inflammatory pre-conditioning, was clearly detected upon long-term consumption of BB phytochemicals. Altogether, the results disclosed herein portray a quiescent mitochondrial-related metabolomics and hint for a unified adaptive response to this nutritional challenge. The beneficial or noxious consequences arising from this dietary trend should be carefully interpreted and necessarily claims future research. [ABSTRACT FROM AUTHOR]

Background The Associating Liver Partition and Portal Ligation for Staged Hepatectomy (ALPPS) depends on a significant inter-stages kinetic growth rate (KGR). Liver regeneration is highly energy-dependent. The metabolic adaptations in ALPPS are unknown. Aims: i) Assess bioenergetics in both stages of ALPPS (T1 and T2) and compare them with control patients undergoing minor (miHp) and major hepatectomy (MaHp), respectively; ii) Correlate findings in ALPPS with volumetric data; iii) Investigate expression of genes involved in liver regeneration and energy metabolism. Methods Five patients undergoing ALPPS, five controls undergoing miHp and five undergoing MaHp. Assessment of remnant liver bioenergetics in T1, T2 and controls. Analysis of gene expression and protein content in ALPPS. Results Mitochondrial function was worsened in T1 versus miHp; and in T2 versus MaHp (p < 0.05); but improved from T1 to T2 (p < 0.05). Liver bioenergetics in T1 strongly correlated with KGR (p < 0.01). An increased expression of genes associated with liver regeneration (STAT3, ALR) and energy metabolism (PGC-1α, COX, Nampt) was found in T2 (p < 0.05). Conclusion Metabolic capacity in ALPPS is worse than in controls, improves between stages and correlates with volumetric growth. Bioenergetic adaptations in ALPPS could serve as surrogate markers of liver reserve and as target for energetic conditioning. [ABSTRACT FROM AUTHOR]

Abstract: The major toxicological concern associated with nanomaterials is the fact that some manufactured nanomaterials are redox active, and some particles transport across cell membranes, especially into mitochondria. Thus, evaluation of their toxicity upon acute exposure is essential. In this work, we evaluated the toxicity of silver nanoparticles (40 and 80nm) and their effects in rat liver mitochondria bioenergetics. Wistar rat liver mitochondria demonstrate alterations in respiration and membrane potential capacities in the presence of either 40 or 80nm silver nanoparticles. Our data demonstrated a statistically significant decrease in mitochondrial membrane potential, ADP-induced depolarization, and respiratory control ratio (RCR) upon exposure to silver nanoparticles. Our results show that silver nanoparticles cause impairment of mitochondrial function, due mainly to alterations of mitochondrial membrane permeability. This results in an uncoupling effect on the oxidative phosphorylation system. Thus, mitochondrial toxicity may have a central role in the toxicity resulting from exposure to silver nanoparticles. [Copyright &y& Elsevier]

Abstract: Non-alcoholic fatty liver disease (NAFLD) is an increasingly reported pathology, characterized by fat accumulation within the hepatocyte. Growing evidences suggest specific effects on mitochondrial metabolism, but it is still unclear the relationship between fatty liver progression and mitochondrial function. In the present work we have investigated the impact of fatty liver on mitochondrial bioenergetic functions and susceptibility to mitochondrial permeability transition (MPT) induction in animals fed a choline-deficient diet (CDD) for 4, 8, 12 or 16 weeks. Mitochondria isolated from CDD animals always exhibited higher state 4 respiration. Mitochondrial membrane potential was decreased in CDD animals at 4 and 16 weeks. At 12 weeks, oxidative phosphorylation was more efficient in CDD animals, suggesting a possible early response trying to revert the deleterious effect of increased triglyceride storage in the liver. However, mitochondrial dysfunction was evident in CDD animals at 16 weeks as indicated by decreased RCR and ADP/O, with a corresponding decrease in respiratory chain enzymes activities. Such loss of respiratory efficiency was associated with accumulation of protein oxidation products, in tissue and mitochondrial fraction. Additionally, although no differences in ATPase activity, the lag phase was increased in mitochondria from CDD animals at 16 weeks, associated with decreased content of the adenine nucleotide translocator. Increased susceptibility to calcium-induced MPT was evident in CDD animals at all time points. These results suggest a dynamic mechanism for the development of NALFD associated with altered mitochondrial function. [Copyright &y& Elsevier]

Abstract: Indirubin, a red colored 3,2′-bisindole isomer, is a component of Indigo naturalis and is an active ingredient used in traditional Chinese medicine for the treatment of chronic diseases. The family of indirubin derivatives, such as indirubin-3′-oxime, has been suggested for various therapeutic indications. However, potential toxic interactions such as indirubin effects on mitochondrial bioenergetics are still unknown. This study evaluated the action of indirubin-3′-oxime on the function of isolated rat liver mitochondria contributing to a better understanding of the biochemical mechanisms underlying the multiple effects of indirubin. Indirubin-3′-oxime incubated with isolated rat liver mitochondria, at concentrations above 10μM, significantly depresses the phosphorylation efficiency of mitochondria as inferred from the decrease in the respiratory control and ADP/O ratios, the perturbations in mitochondrial membrane potential and in the phosphorylative cycle induced by ADP. Furthermore, indirubin-3′-oxime at up to 25μM stimulates the rate of state 4 respiration and inhibits state 3 respiration. The increased lag phase of repolarization was associated with a direct inhibition of the mitochondrial ATPase. Indirubin-3′-oxime significantly inhibited the activity of complex II and IV thus explaining the decreased FCCP-stimulated mitochondrial respiration. Mitochondria pre-incubated with indirubin-3′-oxime exhibits decreased susceptibility to calcium-induced mitochondrial permeability transition. This work shows for the first time multiple effects of indirubin-3′-oxime on mitochondrial bioenergetics thus indicating a potential mechanism for indirubin-3′-oxime effects on cell function. [Copyright &y& Elsevier]