Nutritional effects on mitochondrial bioenergetics. Alterations in oxidative phosphorylation by rat liver mitochondria

A New Quinone-Based Inhibitor of Mitochondrial Complex I in D-Conformation, Producing Invasion Reduction and Sensitization to Venetoclax in Breast Cancer Cells

Mitochondrial Complex I plays a crucial role in the proliferation, chemoresistance, and metastasis of breast cancer (BC) cells. This highlights it as an attractive target for anti-cancer drugs. Using submitochondrial particles, we identified FRV-1, an ortho-carbonyl quinone, which inhibits NADH:duroquinone activity in D-active conformation and reduces the 3ADP state respiration dependent on Complex I, causing mitochondrial depolarization, ATP drop, increased superoxide levels, and metabolic remodeling towards glycolysis in BC cells. Introducing methyl groups at FRV-1 structure produced analogs that acted as electron acceptors at the Complex I level or increased the inhibitory effect of FCCP-stimulated oxygen consumption rate, which correlated with their redox potential, but increased toxicity on RMF-621 human breast fibroblasts was observed. FRV-1 was inactive in the naphthoquinone oxidoreductase 1 (NOQ1)-positive BC cell line, MCF7, but the sensitivity was recovered by dicoumarol, a NOQ1 inhibitor, suggesting that FRV-1 is a NOQ1 substrate. Importantly, FRV-1 selectively inhibited the proliferation, migration, and invasion of NQO1 negative BC cell, MDA-MB-231, in an OXPHOS- and ROS-dependent manner and sensitized it to the BH3 mimetic drug venetoclax. Overall, FRV-1 is a novel Complex I inhibitor in D-active conformation, blocking possibly the re-activation to A-state, producing selective anti-cancer effects in NQO1-negative BC cell lines.

Malnutrition-associated liver steatosis and ATP depletion is caused by peroxisomal and mitochondrial dysfunction

BACKGROUND & AIMS

Severe malnutrition in young children is associated with signs of hepatic dysfunction such as steatosis and hypoalbuminemia, but its etiology is unknown. Peroxisomes and mitochondria play key roles in various hepatic metabolic functions including lipid metabolism and energy production. To investigate the involvement of these organelles in the mechanisms underlying malnutrition-induced hepatic dysfunction we developed a rat model of malnutrition.

METHODS

Weanling rats were placed on a low protein or control diet (5% or 20% of calories from protein, respectively) for four weeks. Peroxisomal and mitochondrial structural features were characterized using immunofluorescence and electron microscopy. Mitochondrial function was assessed using high-resolution respirometry. A novel targeted quantitative proteomics method was applied to analyze 47 mitochondrial proteins involved in oxidative phosphorylation, tricarboxylic acid cycle and fatty acid β-oxidation pathways.

RESULTS

Low protein diet-fed rats developed hypoalbuminemia and hepatic steatosis, consistent with the human phenotype. Hepatic peroxisome content was decreased and metabolomic analysis indicated peroxisomal dysfunction. This was followed by changes in mitochondrial ultrastructure and increased mitochondrial content. Mitochondrial function was impaired due to multiple defects affecting respiratory chain complex I and IV, pyruvate uptake and several β-oxidation enzymes, leading to strongly reduced hepatic ATP levels. Fenofibrate supplementation restored hepatic peroxisome abundance and increased mitochondrial β-oxidation capacity, resulting in reduced steatosis and normalization of ATP and plasma albumin levels.

CONCLUSIONS

Malnutrition leads to severe impairments in hepatic peroxisomal and mitochondrial function, and hepatic metabolic dysfunction. We discuss the potential future implications of our findings for the clinical management of malnourished children.

LAY SUMMARY

Severe malnutrition in children is associated with metabolic disturbances that are poorly understood. In order to study this further, we developed a malnutrition animal model and found that severe malnutrition leads to an impaired function of liver mitochondria which are essential for energy production and a loss of peroxisomes, which are important for normal liver metabolic function.

Selenium and zinc protect brain mitochondrial antioxidants and electron transport chain enzymes following postnatal protein malnutrition

AIMS

Selenium (Se) and zinc (Zn) are trace elements required for optimal brain functions. Thus, the role of Se and Zn against protein malnutrition induced oxidative stress on mitochondrial antioxidants and electron transport chain (ETC) enzymes from rats' brain were investigated.

MAIN METHODS

Normal protein (NP) and low protein (LP) rats were fed with diets containing 16% and 5% casein respectively for a period of 10weeks. Then the rats were supplemented with Se and Zn at a concentration of 0.15mgL(-1) and 227mgL(-1) in drinking water for 3weeks after which the rats were sacrificed.

KEY FINDINGS

The results obtained from the study showed significant (p<0.05) increase in lipid peroxidation (LPO), ROS production, oxidized glutathione (GSSG) levels and mitochondrial swelling and significant (p<0.05) reductions in catalase (CAT) and Mn-superoxide dismutase (Mn-SOD) activities, glutathione (GSH) levels, GSH/GSSG ratio and MTT reduction as a result of LP ingestion. The activities of mitochondrial ETC enzymes were also significantly inhibited in both the cortex and cerebellum of LP-fed rats. Supplementation with either Se or Zn restored the alterations in all the parameters.

SIGNIFICANCE

The study showed that Se and Zn might be beneficial in protecting mitochondrial antioxidants and ETC enzymes against protein malnutrition induced oxidative stress.

Effect of treatment with cadmium on structure-function relationships in rat liver mitochondria: studies on oxidative energy metabolism and lipid/phospholipids profiles

Effects of treatment with a single intraperitoneal injection of cadmium (Cd) on oxidative energy metabolism and lipid/phospholipid profiles of rat liver mitochondria were examined at the end of 1 week and 1 month. Following Cd treatment the body weight increased only in the 1 month group, whereas the liver weight increased in both groups. State 3 and 4 respiration rates in general decreased significantly, with the maximum effect being seen with succinate. The 1 week Cd group showed decreased respiratory activity with glutamate, pyruvate + malate, and succinate as the substrates. In the 1 month Cd-treated group respiration rates recovered with glutamate and pyruvate + malate but not with succinate. All cytochrome contents decreased in the 1 week Cd-treated group but recovered in the 1 month group. ATPase activity registered an increase in both Cd-treated groups. Dehydrogenase activities increased in the 1 week group but decreased in the 1 month Cd-treated group. The mitochondrial cholesterol content increased in the 1 week Cd-treated group. In the 1 week Cd-treated group the lysophospholipid (Lyso), sphingomyelin (SPM), and diphosphatidylglycerol (DPG) components increased. By contrast, the phosphatidylethanolamine (PE) component decreased. In the 1 month Cd-treated group the phosphatidylinositol, phosphatidylserine, and DPG components increased, whereas the Lyso, SPM, and phosphatidylcholine components decreased. The results demonstrate that single-dose Cd treatment can have adverse effects on liver mitochondrial oxidative energy metabolism and lipid/phosphopholipid profiles, which in turn can affect membrane structure-function relationships.

Short-term starvation and mitochondrial dysfunction - a possible mechanism leading to postoperative insulin resistance

BACKGROUND

Preoperative starvation results in the development of insulin resistance. Measures to attenuate the development of insulin resistance, such as preoperative carbohydrate loading, lead to clinical benefits. However, the mechanisms that underlie the development of insulin resistance during starvation and its attenuation by preoperative carbohydrate loading remain to be defined. Insulin resistance associated with type 2 diabetes and ageing has been linked to mitochondrial dysfunction. The metabolic consequences of preoperative starvation and carbohydrate loading and mechanisms linking insulin resistance to impaired mitochondrial function are discussed.

METHODS

Searches of the Medline and Science Citation Index databases were performed using various key words in combinations with the Boolean operators AND, OR and NOT. Key journals, nutrition and metabolism textbooks and the reference lists of key articles were also hand searched.

RESULTS

Animal studies have shown that short-term energy deprivation decreases mitochondrial ATP synthesis capacity and complex activity, and increases oxidative injury. Furthermore, evidence from human studies suggests that the development of insulin resistance during starvation may be linked to impaired mitochondrial function.

CONCLUSIONS

There is evidence from animal studies that short-term starvation causes mitochondrial dysfunction. Future studies should investigate whether mitochondrial dysfunction underlies the development of insulin resistance in patients undergoing elective surgery.

Dexamethasone treatment differentially affects the oxidative energy metabolism of rat brain mitochondria in developing and adult animals

We studied the effect of repeated exposure to dexamethasone (Dex) treatment on rat brain mitochondrial oxidative energy metabolism in developing rats at different postnatal ages, i.e. 2-5 week and in adults. The animals were injected with a dose of 2 mg of Dex/kg body weight at around 7:00 a.m. for three alternative days prior to the day of sacrifice; the control group animals received saline vehicle. We measured rates of respiration with different substrates, viz. glutamate, pyruvate+malate, succinate and ascorbate+TMPD; the contents of individual cytochromes and the dehydrogenases and ATPase activities. Dex treatment, in general, stimulated the state 3 rates of respiration rates in young animals in age-dependent and substrate-specific manner except for the 3 week group, whereas in the adults there was substantial inhibition of the respiration. The pattern of dehydrogenases activities matched with respiration rates. Dex treatment also resulted in uncoupling of the second and third site of phosphorylation in 3-week-old animals and in the adults. The contents of cytochrome aa3, b and ATPase activities decreased significantly after Dex treatment in all the age groups. The results thus emphasize that exposure to repeated Dex treatment can significantly influence the oxidative energy metabolism of brain mitochondria in young growing animals as well as in adults.

Stimulation of oxidative energy metabolism in liver mitochondria from old and young rats by treatment with dehydroepiandrosterone (DHEA). A comparative study

Effects of treatment with DHEA (0.2 or 1.0 mg/kg body weight for 7 days) on oxidative energy metabolism of rat liver mitochondria from old (18-24 month old) and young (8-10 weeks old) male albino rats belonging to Charles-Foster strain were examined. Treatment with 1.0 mg DHEA resulted in increased body weights of the young rats without change in the liver weight. In the old animals the liver weight increased progressively with increasing dose of DHEA without affecting body weight. The state 3 respiration rates in liver mitochondria from old animals were, in general, lower than those in the young rats. The state 3 and state 4 respiration rates increased following DHEA treatment in dose-dependent manner bringing them close to values for young animals or beyond that with the effect being more pronounced at 1.0 mg dose. Treatment with DHEA also stimulated state 3 and state 4 respiration rates in young rats in dose-dependent manner. Contents of cytochrome aa(3), b and c + c(1) increased significantly in old animals in dose-dependent manner. In the young rats the lower dose (0.2 mg) of DHEA was more effective in bringing about a maximum increase in the contents of the cytochromes; the effect declined at the higher dose (1.0 mg). DHEA treatment also stimulated the mitochondrial ATPase activity in the old as well as in the young rats. The dehydrogenases activities were considerably low in the old rats compared to the values for the young animals. Treatment with DHEA stimulated dehydrogenases activities in old rats in dose-dependent manner bringing them close to values for the young animals or beyond. Treatment with lower dose (0.2 mg) of DHEA maximally stimulated dehydrogenases activities in young animals.

The respiratory effects of stanniocalcin-1 (STC-1) on intact mitochondria and cells: STC-1 uncouples oxidative phosphorylation and its actions are modulated by nucleotide triphosphates

Stanniocalcin-1 (STC-1) is one of only a handful of hormones that are targeted to mitochondria. High affinity receptors for STC-1 are present on cytoplasmic membranes and both the outer and inner mitochondrial membranes of nephron cells and hepatocytes. In both cell types, STC-1 is also present within the mitochondrial matrix and receptors presumably enable its sequestration. Furthermore, studies in bovine heart sub-mitochondrial particles have shown that STC-1 has concentration-dependent stimulatory effects on electron transport chain activity. The aim of the present study was to determine if the same effects could be demonstrated in intact, respiring mitochondria. At the same time, we also sought to demonstrate the functionality, if any, of an ATP binding cassette that has only recently been identified within the N-terminus of STC-1 by Prosite analysis. Intact, respiring mitochondria were isolated from rat muscle and liver and exposed to increasing concentrations of recombinant human STC-1 (STC-1). Following a 1h exposure to 500 nM STC-1, mitochondria from both organs displayed significant increases in respiration rate as compared to controls. Moreover, STC-1 uncoupled oxidative phosphorylation as ADP:O ratios were significantly reduced in mitochondria from both tissues. The resulting uncoupling was correlated with enhanced mitochondrial (45)Ca uptake in the presence of hormone. Respiratory studies were also conducted on a mouse inner medullary collecting cell line, where STC-1 had time and concentration-dependent stimulatory effects within the physiological range. In the presence of nucleotide triphosphates such as ATP and GTP (5mM) the respiratory effects of STC-1 were attenuated or abolished. Receptor binding studies revealed that this was due to a four-fold decrease in binding affinity (KD) between ligand and receptor. The results suggest that STC-1 stimulates mitochondrial electron transport chain activity and calcium transport, and that these effects are negatively modulated by nucleotide triphosphates.

Effect of dehydroepiandrosterone (DHEA) treatment on oxidative energy metabolism in rat liver and brain mitochondria. A dose–response study

OBJECTIVES

Effects of treatment with dehydroepiandrosterone (DHEA) on oxidative energy metabolism in rat liver and brain mitochondria were examined.

DESIGN AND METHODS

Young adult rats were administered DHEA (0.1, 0.2, 1.0 or 2.0 mg/kg body weight) by subcutaneous route for 7 consecutive days.

RESULTS

DHEA treatment resulted in general, in stimulation of state 3 respiration rates without having any uncoupling effect on ADP/O ratios. The stimulation of state 3 respiration rate for a given substrate was dose dependent in a tissue-specific manner. Parallel increases in the contents of cytochromes aa(3) and b were also noted. DHEA treatment stimulated the glutamate dehydrogenase (GDH) and succinate DCIP reductase (SDR) activities. Under the treatment conditions, mitochondrial ATPase activity was also stimulated.

CONCLUSIONS

Treatment with DHEA significantly stimulated oxidative energy metabolism in liver and brain mitochondria.

Treatment with dehydroepiandrosterone (DHEA) stimulates oxidative energy metabolism in the liver mitochondria from developing rats

Effects of treatment with DHEA (0.2 mg or 1.0 mg / kg body weight for 7 days) on oxidative energy metabolism on liver mitochondria from developing and young adult rats were examined. Treatment with DHEA resulted in a progressive dose-dependent increase in the liver weights of the developing animals without change in the body weight. In the young adult rats treatment with 1.0 mg DHEA showed increase only in the body weight. Treatment with DHEA stimulated state 3 and state 4 respiration rates in developing as well as young adult rats in dose-dependent manner with all the substrates used; magnitude of stimulation was age-dependent. In young adults the extent of simulation of state 3 respiration rates declined at higher dose (1.0 mg) of DHEA with glutamate and succinate as substrates. Stimulation of state 3 respiration rates was accompanied by increase in contents of cytochrome aa3, b and c + c1 and stimulation of ATPase and dehydrogenases activities in dose- and age-dependent manner.

Effect of Dexamethasone Treatment on Oxidative Energy Metabolism in Rat Liver Mitochondria During Postnatal Developmental Periods

Dexamethasone--a potent synthetic glucocorticoid--has multiple therapeutic applications and is used in all age groups, as well as for antenatal and perinatal treatments. However, side-effects of dexamethasone treatment, including those on development, are becoming increasingly apparent. Since developmental processes are energy-dependent, we examined the effects of chronic dexamethasone treatment on oxidative energy metabolism in liver mitochondria from rats belonging to different developmental age groups. Dexamethasone treatment adversely affected the state 3 respiration rates in 2- and 3-week groups and in the adults with glutamate as the substrates, whereas for pyruvate + malate, the adverse effects were seen for the 3 week and the adult groups. Oxidation of succinate was severely impaired in all the age groups. For ascorbate + TMPD as the substrate, elevated respiration was noted for the 5-week group and the impaired oxidation was observed in adults. Dexamethasone treatment also resulted in site-specific uncoupling with the effect being seen predominantly in the 3- and 5-week and adult animals. The activity of dehydrogenases decreased in a manner comparable to the respiration rates. The mitochondrial cytochromes decreased in an age-dependent manner. The ATPase activity also decreased significantly. The results thus emphasize the adverse effects of dexamethasone treatment on mitochondrial energy metabolism especially in critical age groups.

Alterations of rat liver mitochondrial oxidative phosphorylation and calcium uptake by benzo[a]pyrene

We report that oxidative phosphorylation and Ca2+ uptake processes are enhanced in liver mitochondria isolated from benzo[a]pyrene (B[a]P)-treated rats. The carcinogen did not affect either the respiratory control index or the Ca2+ control ratio. B[a]P treatment increased the oxidation rate of several substrates that donate electrons at the level of all three coupling sites, either the ADP- or Ca2+-stimulated rates or those observed after ADP or Ca2+ exhaustion. However, the efficiency of energy coupling was maintained because both ADP/O and Ca2+/site ratios remained unchanged. The electron flow through NADH-oxidase, NADH-duroquinone reductase, NADH-juglone reductase, NADH-cytochrome c reductase, succinate-cytochrome c reductase, and cytochrome c oxidase was enhanced by B[a]P; however, succinate dehydrogenase activity was not affected. All these effects depended on the time post B[a]P administration, with a greater increase close to 48 h after administration of the carcinogen. The contents of cytochromes b, c1, and a + a3 from liver mitochondria, especially those isolated 48 h after B[a]P, were also significantly increased, although cytochrome c levels was just lightly increased 24 h after B[a]P treatment. These results suggest that B[a]P treatment stimulates mitochondrial respiration by increasing the level of several components of the mitochondrial respiratory chain. This may reflect mitochondrial adaptation to the cellular energy requirements of cell division in the neoplastic transformation process.

Dietary nucleotides modulate mitochondrial function of intestinal mucosa in weanling rats with chronic diarrhea

BACKGROUND

Chronic diarrhea during early infancy is characterized by intestinal mucosal injury, and as a consequence, the mitochondrial system of oxidation and reduction and energy production is altered. Since dietary nucleotides have been associated with the process of intestinal mucosal repair in rats with chronic diarrhea, the aim of this study was to examine the effects of dietary nucleotides on the functioning of mucosal mitochondria.

METHODS

Weanling rats were fed with a semipurified synthetic diet (C) or the same diet in which carbohydrates were substituted by lactose (L), resulting in chronic diarrhea. During recovery, rats were fed with the semipurified synthetic diet (LC) or the same diet supplemented with nucleotides (LN). The activities of adenosine triphosphate synthase (ATPase), cytochrome c oxidase, citrate synthase, and malate dehydrogenase were measured in mitochondria from ileum and colon mucosa.

RESULTS

These enzymatic activities rose in rats with chronic diarrhea, possibly to compensate for the drastic decline in adenosine triphosphate (ATP) synthesis. Dietary nucleotide supplementation allowed normalizing of the activities of ATPase (C: 0.37 +/- 0.16 microg/min/mg protein; L: 0.68 +/- 0.25 microg/min/mg protein; LC: 0.60 +/- 0.20 microg/min/mg protein; LN: 0.42 +/- 0.22 microg/min/mg protein), citrate synthase (C: 0.12 +/- 0.05 mM/min/mg protein; L: 0.21 +/- 0.07 mM/min/mg protein; LC: 0.21 +/- 0.06 mM/min/mg protein; LN: 0.12 +/- 0.02 mM/min/mg protein), and malate dehydrogenase (C: 0.77 +/- 0.48 mM/min/mg protein; L: 3.08 +/- 0.85 mM/min/mg protein; LC: 2.11 +/- 0.44 mM/min/mg protein; LN: 1.13 +/- 0.51 mM/min/mg protein) in the ileum mitochondria of the diarrheic rats. In colonic mucosa, mitochondrial enzymatic activities were restored after eliminating lactose from the diet.

CONCLUSION

These results suggest that dietary nucleotides promote earlier restoration of the ileal mitochondrial function after chronic diarrhea.

Proliferation, functionality, and extracellular matrix production of hepatocytes and a liver stellate cell line: a comparison between single cultures and cocultures

Hepatic fibrosis is a common feature of many chronic liver diseases. Given the ethical considerations of studies with humans and the limited availability of liver biopsies, there is a need for in vitro models to understand the molecular events involved in hepatic fibrosis. The aim of this work was to compare the behavior of two hepatic cell types involved in fibrogenesis: a liver stellate cell line (CFSC-2G) and primary hepatocytes, both in single and mixed cultures. Cell proliferation was measured as DNA synthesis, protein content, and cell cycle study; functionality as adenylate charge, metabolic rate, and albumin content; and extracellular matrix production as type I collagen content, total collagen synthesis/degradation, metalloproteinase-13 content, and interstitial collagenase activity. Protein content and DNA synthesis were higher in CFSC-2G than in cocultures. Adenylate charge, metabolic rate, and albumin content were impaired in cocultures. Type I collagen content and total collagen synthesis were similar in CFSC-2G and cocultures. Metalloproteinase-13 content was higher in CFSC-2G and cocultures compared with hepatocytes, whereas collagenase activity was only detectable in cocultures. These results suggest that the presence of hepatocytes in the cocultures affects negatively the cell proliferation, functionality, and extracellular matrix production. Cocultures of activated CFSC-2G and healthy hepatocytes are a useful model to study fibrogenesis in vitro since various functional alterations found in this pathology are reproduced.

Inhibitory effect of vanillin-like compounds on respiration and growth of adenocarcinoma TA3 and its multiresistant variant TA3-MTX-R

The effects of some imine and amine derivatives of vanillin on the respiration rate of mouse mammary adenocarcinoma TA3 line, its multiresistant variant TA3-MTX-R line and mouse hepatocytes, together with their respective mitochondrial fractions, are described. These derivatives inhibit respiration in both tumour cell lines more effectively than vanillin in the absence or presence of the uncoupler CCCP. Since both types of derivatives block the electron flow, mainly through the NADH-CoQ span, they behave as oxidative phosphorylation inhibitors. Thus, they prevent ATP synthesis and alter cellular processes requiring energy, which would lead to cellular death. Amine derivatives of vanillin present a similar effect on both tumour cell lines, being amine C the most efficient inhibitor. Moreover, mouse hepatocytes are about 4-fold less sensitive to amine C than tumour cells. These amine derivatives are better inhibitors than the corresponding imines; probably because they should interact better with the respiratory chain reaction site.

Effect of hypoenergetic feeding and refeeding on muscle and mononuclear cell activities of mitochondrial complexes I--IV in enterally fed rats

BACKGROUND

Previous studies suggested that cell energetics are altered by malnutrition.

OBJECTIVE

We hypothesized that nutritional manipulations influence mitochondrial enzyme activities of the electron transport chain in both skeletal muscle and blood mononuclear cells.

DESIGN

After a gastrostomy tube was inserted, 44 rats were randomly assigned to 1 of 4 experimental groups: control fed (CF; 364 kJ/d for 7 d), hypoenergetic fed (HF; 92 kJ/d for 7 d), hypoenergetic protein refed (HPR; 92 kJ/d for 7 d and then 129 kJ/d for 1 d), and hypoenergetic glucose refed (HGR; 92 kJ/d for 7 d and then 129 kJ/d for 1 d). The protein and glucose contents of the liquid formulas were different for the HPR and HGR groups. After mitochondria were isolated from the soleus muscle, the activities of complexes I--IV were measured spectrophotometrically. Because of the lack of available tissue, only the activity of complex I was measured in the mononuclear cell extract.

RESULTS

The recovery of complex activities in the CF and HF groups was not significantly different in the mitochondrial fraction of the soleus muscle. Compared with that in the CF group, the activities of complexes I--III in the mitochondrial fraction of the soleus muscle and the activity of complex I in mononuclear cells were significantly lower in the HF group. The activities of complexes I--III in the mitochondrial fraction of the soleus muscle and the activity of complex I in mononuclear cells were significantly higher in the HPR than in the HF group. The activity of complex IV was generally not affected by nutritional manipulations.

CONCLUSION

Malnutrition decreases activities of mitochondrial complexes, which are restored by protein but not glucose refeeding.

Effect of catecholamine depletion on oxidative energy metabolism in rat liver, brain and heart mitochondria; use of reserpine

Regulation of mitochondrial functions in vivo by catecholamines was examined indirectly by depleting the catecholamines stores by reserpine treatments of the experimental animals. Reserpine treatment resulted in decreased respiratory activity in liver and brain mitochondria with the two NAD+-linked substrates: glutamate and pyruvate + malate with succinate ATP synthesis rate decreased in liver mitochondria only. With ascorbate + TMPD system, the ADP/O ratio and ADP phosphorylation rate decreased in brain mitochondria. For the heart mitochondria, state 3 respiration rates decreased for all substrates. In the liver mitochondria basal ATPase activity decreased by 51%, but in the presence of Mg2+ and/or DNP increased significantly. In the brain and heart mitochondria ATPase activities were unchanged. The energy of activation in high temperature range increased liver mitochondrial ATPase while in brain mitochondria reserpine treatment resulted in abolishment in phase transition. Total phospholipid (TPL) content of the brain mitochondria increased by 22%. For the heart mitochondria TPL content decreased by 19% and CHL content decreased by 34%. Tissue specific differential effects were observed for the mitochondrial phospholipid composition. Liver mitochondrial membranes were more fluidized in the reserpine-treated group. The epinephrine and norepinephrine contents in the adrenals decreased by 68 and 77% after reserpine treatment.

Effect of aluminium-induced Alzheimer like condition on oxidative energy metabolism in rat liver, brain and heart mitochondria

Prolonged exposure of rats to aluminium (Al) can result in an Alzheimer-like condition. To get better insights into the biochemical defects underlying AD, senility and ageing we exposed rats for long durations (90-100 days) to soluble salt of aluminium (AlCl3) and checked its influence on mitochondrial respiratory activity in the liver, brain and heart. In the liver and brain mitochondria the ADP/O ratio was impaired with NAD+ linked substrates. State three respiration decreased with glutamate in the liver. For succinate, the ADP/O ratio decreased in the liver mitochondria while state three and four respiration decreased in the brain mitochondria. In both the tissues respiration rates decreased with ascorbate + TMPD as the substrate. In the heart mitochondria ADP/O ratios with NAD+ linked substrates decreased, while respiration rates increased with all the substrates except for ascorbate + TMPD. Temperature kinetics data showed different effects on ATPase in the mitochondria from the three tissues. Data on lipid/phospholipid profiles suggested that the observed changes in energy metabolism were not mediated via lipid changes. Long-term exposure to Al resulted in approximately 100% increase in Al content of liver and brain mitochondria but in the heart there was phenomenal 11-fold increase, indicating thereby that the effects of Al exposure were indirect rather than direct due to Al accumulation.

Ethanol intake: effect on liver and brain mitochondrial function and acetaldehyde oxidation

The effect of a chronic ethanol consumption by forcing rats to drink a 20% v/v ethanol solution as sole drinking fluid, for 3 months, was evaluated on: liver and brain mitochondrial function, the capacity of isolated mitochondria to oxidize acetaldehyde, as well as on the low Km mitochondrial AlDH activity, in rats. The O2 uptake by liver and brain mitochondria in the presence of glutamate + malate, succinate or ascorbate + TMPD, was measured polarographically with a Clark electrode. Acetaldehyde oxidation was measured by the disappearance rate in presence of the intact or disrupted mitochondria (AlDH activity) by gas chromatography. Results indicate that an ethanol intake of 11 g/kg b.wt. per day produce a significant reduction of the liver mitochondrial respiration tested with all the substrates used, including acetaldehyde. In contrast, the activity of AlDH in disrupted mitochondria remained unchanged. These results are in accord with the idea that a progressive deterioration of liver mitochondrial function appears with the increase in amount of ethanol consumed, and that alterations of acetaldehyde oxidation by intact mitochondria can be detected before an alteration of the AlDH activity. Concerning the brain, this ethanol consumption regimen did not affect the brain mitochondrial respiration tested with glutamate + malate, succinate or ascorbate + TMPD, but it induces an increase in acetaldehyde oxidation rate by intact brain mitochondria. The imposed increase in the cerebral aldehyde oxidizing capacity could reflect a principal biochemical mechanism underlying neural adaptation to ethanol.

Altered energy coupling in rat heart mitochondria following in vivo treatment with propranolol

Effects of acute and chronic treatment with propranolol on oxidative phosphorylation in rat heart mitochondria were examined. Acute propranolol treatment resulted in inhibition of coupled respiration with pyruvate + malate and succinate as substrates. Chronic treatment resulted in decreased state 3 respiration rates with all the substrates employed. The net effect of propranolol treatment was decreased ATP-phosphorylation rates suggesting that this was possibly one of the modes of its cardiodepressant activity. Additionally, chronic propranolol treatment brought about a decrease in the content of cytochrome c + c1 in heart mitochondria. Estimation of propranolol concentrations in serum, whole tissue homogenate and heart mitochondria indicated that although the mitochondria accumulated the highest amount of the drug, the intramitochondrial concentration of the drug was one or two orders of magnitude lower than that which is required to bring about inhibition of respiration under in vitro conditions. Besides, the concentrations reached under acute and chronic treatment conditions were almost comparable. The results, therefore, suggest that the action of the drug in vivo may involve more intricate mechanisms than those observed under in vitro conditions.

Impaired mitochondrial oxidative energy metabolism following paracetamol-induced hepatotoxicity in the rat

1. Effects of paracetamol treatment in vivo at subtoxic (375 mg kg-1 body weight) and toxic (750 mg kg-1 body weight) doses on energy metabolism in rat liver mitochondria were examined. 2. Paracetamol treatment resulted in a significant loss in body weights without affecting the liver protein contents. Toxic doses, however, resulted in 21% decrease in the yield of mitochondrial proteins. 3. Subtoxic doses of paracetamol did not, in general, affect the respiratory parameters in the liver mitochondria except in the case of succinate where both the state 3 respiration and the ADP-phosphorylation rates increased by 28%. 4. Toxic doses of paracetamol caused 25 to 47% decrease in the state 3 respiration rates depending on the substrate used. ADP/O ratios also decreased significantly with pyruvate + malate and succinate as the substrates. Consequently, ADP-phosphorylation was impaired significantly from 20 to 63%. 5. Subtoxic doses of paracetamol resulted in increased contents of cytochrome c + c1 while the toxic doses caused lowering of the cytochromes aa3 and b contents. 6. Glutamate and succinate dehydrogenase activities decreased in both the experimental groups while Mg2+-ATPase activity was impaired only after toxic dose-treatment. 7. The results show that toxic doses of paracetamol result in impaired energy coupling in the liver mitochondria. Effects of subtoxic doses were also demonstrable in terms of impaired dehydrogenases activities.

Effects of guanethidine on electron transport and proton movements in rat heart, brain and liver mitochondria

Guanethidine at 5-25 mM concentrations was found to induce up to 79% inhibition of ADP-stimulated (state III) oxygen consumption in isolated rat heart, brain or liver mitochondria, when the added substrate was glutamate or succinate, but the inhibition was considerably lower (24% or less) when respiration was supported by ascorbate plus tetramethylphenylenediamine (TMPD). Comparable results were seen regarding ADP-stimulated proton uptake, where even greater inhibition (up to 94% with glutamate or succinate, but not ascorbate plus TMPD) was found. Similar but somewhat less marked effects were also seen in resting (state IV) respiration and on the acceptor control ratio (state III/state IV respiration). 2,4-Dinitrophenol was unable to relieve guanethidine-induced inhibition of electron transport. These results indicate that guanethidine inhibits primarily mitochondrial electron transport itself, and that the site where such inhibition is more marked is located in the span between ubiquinone and cytochrome c of the respiratory chain. It is, therefore, suggested that active guanethidine uptake by noradrenergic neurons can lead to a high drug concentration in their cytoplasm and hence to mitochondrial alterations that can contribute to the pharmacological effect of this drug. Our results demonstrate the interaction between guanethidine and the electron transport chain of mitochondria derived from different tissues and, therefore, support this hypothesis.