Decrease in mitochondrial energy coupling by thyroid hormones: a physiological effect rather than a pathological hyperthyroidism consequence

FV-429 Induced Apoptosis Through ROS-Mediated ERK2 Nuclear Translocation and p53 Activation in Gastric Cancer Cells

Following our previous finding which revealed that FV-429 induces apoptosis in human hepatocellular carcinoma HepG2 cells, in this study, we found that FV-429 could also induce apoptosis in human gastric cancer cells. Firstly, FV-429 inhibited the viability of BGC-823 and MGC-803 cells with IC50 values in the range of 38.10 ± 6.28 and 31.53 ± 6.84 µM for 24 h treatment by MTT-assay. Secondly, FV-429 induced apoptosis in BGC-823 and MGC-803 cells through the mitochondrial-mediated pathway, showing an increase in Bax/Bcl-2 ratios, and caspase-9 activation, without change in caspase-8. Further research revealed that the mitogen-activated protein kinases, including c-Jun N-terminal kinase, extracellular regulated kinase, and p38 mitogen-activated protein kinase, could be activated by FV-429-induced high level ROS. Moreover, FV-429 also promoted the ERK2 nuclear translocation, resulting in the co-translocation of p53 to the nucleus and increased transcription of p53-regulated proapoptotic genes. FV-429 significantly inhibited the nude mice xenograft tumors growth of BGC-823 or MGC-803 cells in vivo.

Ginsenoside F(2) induces apoptosis in humor gastric carcinoma cells through reactive oxygen species-mitochondria pathway and modulation of ASK-1/JNK signaling cascade in vitro and in vivo

Ginsenoside F(2) (F(2)) is a potential bioactive metabolite of major ginsenosides. The potential anti-cancer effect of F(2) in gastric cancer cells has not been appraised. This study investigated the effects of F(2) on the production of reactive oxygen species (ROS). We also investigated the in vitro and in vivo effects of F(2) on the downstream signaling pathways leading to apoptosis in human gastric cancer cells. The in vitro data revealed that F(2) induces ROS accumulation followed by a decrease in mitochondrial transmembrane potential (MTP), and the release of cytochrome c (cyto c), which induced the caspase-dependent apoptosis. Further assay indicated that modulation of ASK-1/JNK pathway contributes to apoptosis. In vivo, F(2) exhibits the obvious anti-cancer effect compared with cisplatin with no obvious toxicity. Jointly, these results suggest that F(2) induces apoptosis by causing an accumulation of ROS and activating the ASK-1/JNK signaling pathway. This provides further support for the use of F(2) as a novel anticancer therapeutic candidate.

HQS-3, a newly synthesized flavonoid, possesses potent anti-tumor effect in vivo and in vitro

HQS-3 is a newly baicalein derivative with a benzene substitution. We investigated the anticancer effect of HQS-3 in vivo and in vitro. HQS-3 significantly decreased tumor growth in mice inoculated with Heps and HepG2 cells; and had little influence on the state and weight of animals. After treatment with 20 mg/kg HQS-3, the inhibitory rate of tumor weight in mice inoculated with Heps and HepG2 cells were 63.62% and 68.03%, respectively. Meanwhile, HQS-3 inhibited the viability of various kinds of tumor cells with IC50 values in the range of 22.98-54.32 μM after 48 h treatment measured by MTT-assay. HQS-3 remarkably inhibited viability of hepatoma cells in a concentration- and time-dependent manner and induced apoptosis in HepG2 cells by DAPI staining and Annexin V/PI double staining. The apoptosis-induction effect of HQS-3 was attributed to its ability to modulate the activity of caspase-9, caspase-3 and PARP. Moreover, the expression of bax protein was increased while the bcl-2 protein was decreased, leading to an increase in Bax/Bcl-2 ratio. The accumulation of ROS induced by HQS-3 in HepG2 cells was also observed. The further results suggested that HQS-3 induced mitochondrial-mediated apoptosis by increasing ROS level and inhibiting the expression of anti-oxidative protein SOD2. HQS-3 exerted anti-tumor activity both in vitro and in vivo via inducing tumor cells apoptosis, and these results suggested that it deserves further investigation as a novel chemotherapy for human tumors.

Utilization of dietary glucose in the metabolic syndrome

This review is focused on the fate of dietary glucose under conditions of chronically high energy (largely fat) intake, evolving into the metabolic syndrome. We are adapted to carbohydrate-rich diets similar to those of our ancestors. Glucose is the main energy staple, but fats are our main energy reserves. Starvation drastically reduces glucose availability, forcing the body to shift to fatty acids as main energy substrate, sparing glucose and amino acids. We are not prepared for excess dietary energy, our main defenses being decreased food intake and increased energy expenditure, largely enhanced metabolic activity and thermogenesis. High lipid availability is a powerful factor decreasing glucose and amino acid oxidation. Present-day diets are often hyperenergetic, high on lipids, with abundant protein and limited amounts of starchy carbohydrates. Dietary lipids favor their metabolic processing, saving glucose, which additionally spares amino acids. The glucose excess elicits hyperinsulinemia, which may derive, in the end, into insulin resistance. The available systems of energy disposal could not cope with the excess of substrates, since they are geared for saving not for spendthrift, which results in an unbearable overload of the storage mechanisms. Adipose tissue is the last energy sink, it has to store the energy that cannot be used otherwise. However, adipose tissue growth also has limits, and the excess of energy induces inflammation, helped by the ineffective intervention of the immune system. However, even under this acute situation, the excess of glucose remains, favoring its final conversion to fat. The sum of inflammatory signals and deranged substrate handling induce most of the metabolic syndrome traits: insulin resistance, obesity, diabetes, liver steatosis, hyperlipidemia and their compounded combined effects. Thus, a maintained excess of energy in the diet may result in difficulties in the disposal of glucose, eliciting inflammation and the development of the metabolic syndrome.

The adaptation of human embryonic stem cells to different feeder-free culture conditions is accompanied by a mitochondrial response

The mitochondrial contribution to the maintenance of human embryonic stem cell (hESC) pluripotency and culture homeostasis remains poorly understood. Here, we sought to determine whether hESC adaptation to different feeder-free culture conditions is linked to a mitochondrial adaptation. The expression of ESC pluripotency factors and parameters of mitochondrial contribution including mitochondrial membrane potential, mtDNA content, and the expression of master mitochondrial genes implicated in replication, transcription, and biogenesis were determined in 8 hESC lines maintained in 2 distinct human feeders-conditioned media (CM): human foreskin fibroblast-CM (HFF-CM) and mesenchymal stem cell-CM (MSC-CM). We show a robust parallel trend between the expression of ESC pluripotency factors and the mitochondrial contribution depending on the culture conditions employed to maintain the hESCs, with those in MSC-CM consistently displaying increased levels of pluripotency markers associated to an enhanced mitochondrial contribution. The differences in the mitochondrial status between hESCs maintained in MSC-CM versus HFF-CM respond to coordinated changes in mitochondrial gene expression and biogenesis. Importantly, the culture conditions determine the mitochondrial distribution within the stage-specific embryonic antigen 3 positive (SSEA3(+)) and negative (SSEA3(-)) isolated cell subsets. hESC colonies in MSC-CM display an "intrinsic" high mitochondrial status which may suffice to support undifferentiated growth, whereas hESC colonies maintained in HFF-CM show low mitochondrial status, possibly relying on the production of autologous niche with higher mitochondrial status to support pluripotency and culture homeostasis. Pluripotency markers and mitochondrial status are concomitantly reverted on changing the culture conditions, supporting an unrecognized role of the mitochondria in response to hESC culture adaptation. We provide the first evidence supporting that hESCs adaptation to different feeder-free culture systems relies on a mitochondrial response.

Reactive oxygen species-mitochondria pathway involved in LYG-202-induced apoptosis in human hepatocellular carcinoma HepG(2) cells

Previously, we demonstrated that LYG-202, a newly synthesized flavonoid with a piperazine substitution, exhibited obvious antitumor activity in vivo and in vitro. The exact mechanism of this new compound remains unclear. In the present study, we examined the effects of LYG-202 on reactive oxygen species (ROS) production and the downstream signaling pathway in the apoptosis of human hepatocellular carcinoma HepG(2) cells. Pretreatment with NAC (N-acetylcysteine), a ROS production inhibitor, partly inhibited the apoptosis induced by LYG-202 via blocking the ROS generation. Further data revealed that LYG-202 induced ROS accumulation followed by a decrease in mitochondrial membrane potential (MMP), release of cytochrome c (Cyt c) and apoptosis-inducing factor (AIF) to cytosol, which induced apoptosis of the cells. Moreover, the mitogen-activated protein kinases (MAPK), the downstream effect of ROS accumulation including c-Jun N-terminal kinase (JNK) and p38 MAPK, could be activated by LYG-202. Taken together, the generation of ROS might play an important role in LYG-202-induced mitochondrial apoptosis pathway, which provided further support for LYG-202 as a novel anticancer therapeutic candidate.

Gating of the mitochondrial permeability transition pore by long chain fatty acyl analogs in vivo

The role played by long chain fatty acids (LCFA) in promoting energy expenditure is confounded by their dual function as substrates for oxidation and as putative classic uncouplers of mitochondrial oxidative phosphorylation. LCFA analogs of the MEDICA (MEthyl-substituted DICarboxylic Acids) series are neither esterified into lipids nor beta-oxidized and may thus simulate the uncoupling activity of natural LCFA in vivo, independently of their substrate role. Treatment of rats or cell lines with MEDICA analogs results in low conductance gating of the mitochondrial permeability transition pore (PTP), with 10-40% decrease in the inner mitochondrial membrane potential. PTP gating by MEDICA analogs is accounted for by inhibition of Raf1 expression and kinase activity, resulting in suppression of the MAPK/RSK1 and the adenylate cyclase/PKA transduction pathways. Suppression of RSK1 and PKA results in a decrease in phosphorylation of their respective downstream targets, Bad(Ser-112) and Bad(Ser-155). Decrease in Bad(Ser-112, Ser-155) phosphorylation results in increased binding of Bad to mitochondrial Bcl2 with concomitant displacement of Bax, followed by PTP gating induced by free mitochondrial Bax. Low conductance PTP gating by LCFA/MEDICA may account for their thyromimetic calorigenic activity in vivo.

Semiquantitative RT-PCR measurement of gene expression in rat tissues including a correction for varying cell size and number

Background

Current methodology of gene expression analysis limits the possibilities of comparison between cells/tissues of organs in which cell size and/or number changes as a consequence of the study (e.g. starvation). A method relating the abundance of specific mRNA copies per cell may allow direct comparison or different organs and/or changing physiological conditions.

Methods

With a number of selected genes, we analysed the relationship of the number of bases and the fluorescence recorded at a present level using cDNA standards. A lineal relationship was found between the final number of bases and the length of the transcript. The constants of this equation and those of the relationship between fluorescence and number of bases in cDNA were determined and a general equation linking the length of the transcript and the initial number of copies of mRNA was deduced for a given pre-established fluorescence setting. This allowed the calculation of the concentration of the corresponding mRNAs per g of tissue. The inclusion of tissue RNA and the DNA content per cell, allowed the calculation of the mRNA copies per cell.

Results

The application of this procedure to six genes: Arbp, cyclophilin, ChREBP, T4 deiodinase 2, acetyl-CoA carboxylase 1 and IRS-1, in liver and retroperitoneal adipose tissue of food-restricted rats allowed precise measures of their changes irrespective of the shrinking of the tissue, the loss of cells or changes in cell size, factors that deeply complicate the comparison between changing tissue conditions. The percentage results obtained with the present methods were essentially the same obtained with the delta-delta procedure and with individual cDNA standard curve quantitative RT-PCR estimation.

Conclusion

The method presented allows the comparison (i.e. as copies of mRNA per cell) between different genes and tissues, establishing the degree of abundance of the different molecular species tested.

The Amaryllidaceae isocarbostyril narciclasine induces apoptosis by activation of the death receptor and/or mitochondrial pathways in cancer cells but not in normal fibroblasts

Our study has shown that the Amaryllidaceae isocarbostyril narciclasine induces marked apoptosis-mediated cytotoxic effects in human cancer cells but not in normal fibroblasts by triggering the activation of the initiator caspases of the death receptor pathway (caspase-8 and caspase-10) at least in human MCF-7 breast and PC-3 prostate carcinoma cells. The formation of the Fas and death receptor 4 (DR4) death-inducing signaling complex was clearly evidenced in MCF-7 and PC-3 cancer cells. Caspase-8 was found to interact with Fas and DR4 receptors on narciclasine treatment. However, narciclasine-induced downstream apoptotic pathways in MCF-7 cells diverged from those in PC-3 cells, where caspase-8 directly activated effector caspases such as caspase-3 in the absence of any further release of mitochondrial proapoptotic effectors. In contrast, in MCF-7 cells, the apoptotic process was found to require an amplification step that is mitochondria-dependent, with Bid processing, release of cytochrome c, and caspase-9 activation. It is postulated that the high selectivity of narciclasine to cancer cells might be linked, at least in part, to this activation of the death receptor pathway. Normal human fibroblasts appear approximately 250-fold less sensitive to narciclasine, which does not induce apoptosis in these cells probably due to the absence of death receptor pathway activation.

Potential involvement of mammalian and avian uncoupling proteins in the thermogenic effect of thyroid hormones

Thyroid hormones (THs) have long been known to be involved in the control of thermoregulation in birds and mammals. In particular, they are reported to play a role in the regulation of heat production. The underlying mechanisms could be the stimulation of the nuclear and mitochondrial transcription of several genes involved in energy metabolism and/or a direct action on the activity of components of the mitochondrial respiratory chain. Attention has recently been focussed on a subfamily of mitochondrial anion carriers called uncoupling proteins (UCPs). These proteins are suspected to be involved in a partial dissipation of the mitochondrial proton electrochemical gradient that would uncouple phosphorylations from oxidations and hence produce heat. However, the involvement of uncoupling mechanisms in thermogenesis and particularly in the thermogenic effect of TH is still unclear. The thermogenic role of UCP1, specifically expressed in brown adipose tissue, and its regulation by TH in rodents is quite well recognised, but the involvement in heat production of its mammalian homologues UCP2, ubiquitously expressed, and UCP3, muscle and adipose tissue-specific, as well as the role of the muscular avian UCP (avUCP), are to be further investigated. The expression of the UCP2 and UCP3 genes was shown to be enhanced by TH in muscle of several rodent species, and to be increased in situations where thermogenesis is stimulated, whereas results are more contrasted in pig. There is now increasing evidence that the physiological role of the mammalian UCP3 and UCP2 is rather related to lipid oxidation and/or prevention of reactive oxygen species accumulation than to heat production by uncoupling. The expression of avUCP was also recently demonstrated to be strongly regulated by thyroid status in chicken, and overexpressed in experimental conditions favouring high triiodothyronine concentrations and thermogenesis. However, its real uncoupling activity and contribution to thermogenesis remain to be established.

Adaptive activation of thyroid hormone and energy expenditure

The mechanisms by which thyroid hormone accelerates energy expenditure are poorly understood. In the brown adipose tissue (BAT), activation of thyroid hormone by type 2 iodothyronine deiodinase (D2) has been known to play a role in adaptive energy expenditure during cold exposure in human newborns and other small mammals. Although BAT is not present in significant amounts in normal adult humans, recent studies have found substantial amounts of D2 in skeletal muscle, a metabolically relevant tissue in humans. This article reviews current biological knowledge about D2 and adaptive T3 production and their roles in energy expenditure.

Intracellular generation of reactive oxygen species by mitochondria

Mitochondria have bioenergetic properties that strongly suggest their involvement in the cellular formation of reactive oxygen species (ROS). Apparent confirmation of this process has come from work with isolated mitochondria, which have been shown to produce H(2)O(2) from dismutating superoxide radicals. Two different sites were reported to shuttle single electrons to oxygen out of the normal respiratory sequence. However, the mechanisms for ROS formation at these two sites are controversial. Arguments against mitochondrial ROS formation in the living cell are based on the fact that bioenergetic alterations may result from the mechanical removal of mitochondria from their natural environment. Furthermore, the invasive detection methods that are generally used may be inappropriate because of the possible interaction of the detection system with mitochondrial constituents. The use of non-invasive detection methods has proved that ROS formation does not occur unless changes in the physical state of the membrane are established. The aim of this commentary is to discuss critically the arguments in favor of mitochondria as the main intracellular source of ROS. The pros and cons of working with isolated mitochondria, as well as the detection methodology are carefully analyzed to judge whether or not the above assumption is correct. The conclusion that mitochondria are the main ROS generators in the cell contradicts the fact that ROS release was not observed. However, if electron flow from ubiquinol to the bc(1) complex is hindered due to changes in lipid fluidity, single electrons may transfer to dioxygen and produce H(2)O(2) via superoxide radicals.

Skeletal muscle mitochondrial free-fatty-acid content and membrane potential sensitivity in different thyroid states: involvement of uncoupling protein-3 and adenine nucleotide translocase

The effect of triiodothyronine (T3) on mitochondrial efficiency could be related to an increase in the concentrations of some proteins, such as uncoupling proteins (UCPs). Free fatty acids (FFA) seem to be a cofactor essential for the uncoupling activity of UCP3. In this paper, we report that the hypothyroidism-hyperthyroidism transition is accompanied by increases: (i) in the endogenous levels of mitochondrial FFA and (ii) in the sensitivity to FFA shown by the mitochondrial respiration rate and membrane potential, which correlated with the level of UCP3 protein. The level of the mRNA for adenine-nucleotide translocase-1 (ANT) was not affected by the thyroid state, while the ANT contribution to FFA-induced changes in mitochondrial uncoupling was low in the hypothyroid and euthyroid states but became more relevant in the hyperthyroid state at the highest concentration of FFA.

Thyroid status is a key regulator of both flux and efficiency of oxidative phosphorylation in rat hepatocytes

Thyroid status is crucial in energy homeostasis, but despite extensive studies the actual mechanism by which it regulates mitochondrial respiration and ATP synthesis is still unclear. We studied oxidative phosphorylation in both intact liver cells and isolated mitochondria from in vivo models of severe not life threatening hyper- and hypothyroidism. Thyroid status correlated with cellular and mitochondrial oxygen consumption rates as well as with maximal mitochondrial ATP production. Addition of a protonophoric uncoupler, 2,4-dinitrophenol, to hepatocytes did not mimic the cellular energetic change linked to hyperthyroidism. Mitochondrial content of cytochrome oxidase, ATP synthase, phosphate and adenine nucleotide carriers were increased in hyperthyroidism and decreased in hypothyroidism as compared to controls. As a result of these complex changes, the maximal rate of ATP synthesis increased in hyperthyroidism despite a decrease in ATP/O ratio, while in hypothyroidism ATP/O ratio increased but did not compensate for the flux limitation of oxidative phosphorylation. We conclude that energy homeostasis depends on a compromise between rate and efficiency, which is mainly regulated by thyroid hormones.

Flow cytometry of isolated mitochondria during development and under some pathological conditions

Mitochondria play an essential role in the generation of the energy needed for eukaryotic cell life and in the release of molecules involved in initiation of cell death. Here we review the changes in isolated mitochondrial fluorescent populations as distinguished by flow cytometry during postnatal development and their regulation by thyroid hormones and catecholamines. The use of flow cytometry in the study of mitochondrial changes occurring under hypothyroidism, alcohol abuse and aging is also reviewed.

Mitochondrial respiratory chain adjustment to cellular energy demand

Because adaptation to physiological changes in cellular energy demand is a crucial imperative for life, mitochondrial oxidative phosphorylation is tightly controlled by ATP consumption. Nevertheless, the mechanisms permitting such large variations in ATP synthesis capacity, as well as the consequence on the overall efficiency of oxidative phosphorylation, are not known. By investigating several physiological models in vivo in rats (hyper- and hypothyroidism, polyunsaturated fatty acid deficiency, and chronic ethanol intoxication) we found that the increase in hepatocyte respiration (from 9.8 to 22.7 nmol of O(2)/min/mg dry cells) was tightly correlated with total mitochondrial cytochrome content, expressed both per mg dry cells or per mg mitochondrial protein. Moreover, this increase in total cytochrome content was accompanied by an increase in the respective proportion of cytochrome oxidase; while total cytochrome content increased 2-fold (from 0.341 +/- 0.021 to 0.821 +/- 0.024 nmol/mg protein), cytochrome oxidase increased 10-fold (from 0.020 +/- 0.002 to 0.224 +/- 0.006 nmol/mg protein). This modification was associated with a decrease in the overall efficiency of the respiratory chain. Since cytochrome oxidase is well recognized for slippage between redox reactions and proton pumping, we suggest that this dramatic increase in cytochrome oxidase is responsible for the decrease in the overall efficiency of respiratory chain and, in turn, of ATP synthesis yield, linked to the adaptive increase in oxidative phosphorylation capacity.

Control of energy metabolism by iodothyronines

One of the most widely recognized effects of thyroid hormones (TH) in adult mammals is their influence over energy metabolism. In the past, this has received much attention but, possibly because of the complex mode of action of thyroid hormones, no universally accepted mechanism to explain this effect has been put forward so far. Significant advances in our understanding of the biochemical processes involved in the actions of TH have been made in the last three decades and now it seems clear that TH can act through both nuclear-mediated and extranuclear-mediated pathways. TH increase energy expenditure, partly by reducing metabolic efficiency, with control of specific genes at the transcriptional level, being is thought to be the major molecular mechanism. However, both the number and the identity of the thyroid-hormone-controlled genes remain unknown, as do their relative contributions. The recent discovery of uncoupling proteins (UCPs) (in addition to UCP1 in brown adipose tissue) in almost all tissues in animals, including humans, has opened new perspectives on the understanding of the mechanisms involved in the regulation of energy metabolism by thyroid hormones. Other approaches have included the various attempts made to attribute changes in respiratory activity to a direct influence of thyroid hormones over the mitochondrial energy-transduction apparatus. In addition, an increasing number of studies has revealed that TH active in the regulation of energy metabolism include not only T3, but also other iodothyronines present in the biological fluids, such as 3,5-diiodothyronine (3,5-T2). This, in turn, may make it possible to explain some of the effects exerted by TH on energy metabolism that cannot easily be attributed to T3.

T(3) increases mitochondrial ATP production in oxidative muscle despite increased expression of UCP2 and -3

Triiodothyronine (T(3)) increases O(2) and nutrient flux through mitochondria (Mito) of many tissues, but it is unclear whether ATP synthesis is increased, particularly in different types of skeletal muscle, because variable changes in uncoupling proteins (UCP) and enzymes have been reported. Thus Mito ATP production was measured in oxidative and glycolytic muscles, as well as in liver and heart, in rats administered T(3) for 14 days. Relative to saline-treated controls, T(3) rats had 80, 168, and 62% higher ATP production in soleus muscle, liver, and heart, respectively, as well as higher activities of citrate synthase (CS; 63, 90, 25%) and cytochrome c oxidase (COX; 119, 225, 52%) in the same tissues (all P < 0.01). In plantaris muscle of T(3) rats, CS was only slightly higher (17%, P < 0.05) than in controls, and ATP production and COX were unaffected. mRNA levels of COX I and III were 33 and 47% higher in soleus of T(3) rats (P < 0.01), but there were no differences in plantaris. In contrast, UCP2 and -3 mRNAs were 2.5- to 14-fold higher, and protein levels were 3- to 10-fold higher in both plantaris and soleus of the T(3) group. We conclude that T(3) increases oxidative enzymes and Mito ATP production and Mito-encoded transcripts in oxidative but not glycolytic rodent tissues. Despite large increases in UCP expression, ATP production was enhanced in oxidative tissues and maintained in glycolytic muscle of hyperthyroid rats.

Inhibition of heart mitochondrial lipid peroxidation by non-toxic concentrations of carvedilol and its analog BM-910228

Carvedilol, a non-selective beta-adrenoreceptor blocker, has been shown to possess a high degree of cardioprotection in experimental models of myocardial damage. Reactive oxygen species have been proposed to be implicated in such situations, and antioxidants have been demonstrated to provide partial protection to the reported damage. The purpose of our study was to investigate the antioxidant effect of carvedilol and its metabolite BM-910228 by measuring the extent of lipid peroxidation in a model of severe oxidative damage induced by ADP/FeSO(4) in isolated rat heart mitochondria. Carvedilol and BM-910228 inhibited the thiobarbituric acid-reactive substance formation and oxygen consumption associated with lipid peroxidation with IC(50) values of 6 and 0.22 microM, respectively. Under the same conditions, the IC(50) values of alpha-tocopheryl succinate and Trolox were 125 and 31 microM, respectively. As expected, the presence of carvedilol and BM-910228 preserved the structural and functional integrity of mitochondria under oxidative stress conditions for the same concentration range shown to inhibit lipid peroxidation, since they prevented the collapse of the mitochondrial membrane potential (DeltaPsi) induced by ADP/FeSO(4) in respiring mitochondria. It should be stressed that neither carvedilol nor BM-910228 induced any toxic effect on mitochondrial function in the concentration range of the compounds that inhibits the peroxidation of mitochondrial membranes. In conclusion, the antioxidant properties of carvedilol may contribute to the cardioprotective effects of the compound, namely through the preservation of mitochondrial functions whose importance in myocardial dysfunction is clearly documented. Additionally, its hydroxylated analog BM-910220, with its notably superior antioxidant activity, may significantly contribute to the therapeutic effects of carvedilol.

Short-term hypothermia activates hepatic mitochondrial sn-glycerol-3-phosphate dehydrogenase and thermogenic systems

The contribution of the sn-glycerol-3-phosphate (G-3-P) shuttle in the control of energy metabolism is well established. It is also known that its activity may be modulated by hormones involved in thermogenesis, such as thyroid hormones or dehydroepiandrosterone and its metabolites, that act by inducing de novo synthesis of mitochondrial G-3-P dehydrogenase (mGPDH). However, little is known as to the factors that may influence the activity without enzyme induction. In the present study we investigated the possible role of the G-3-P shuttle in the thermogenic response to different hypothermic stresses. It was found that a decrease of body temperature causes the liver rapidly to enhance mGPDH activity and G-3-P-dependent respiration. The enhancement, which does not result from de novo synthesis of enzymes, has the potential of increasing heat production both by decreased ATP synthesis during the oxidation of G-3-P and by activation of the glycolytic pathway.

Changes in intramitochondrial cardiolipin distribution in apoptosis-resistant HCW-2 cells, derived from the human promyelocytic leukemia HL-60

Using a cytofluorimetric approach, we studied intramitochondrial cardiolipin (CL) distribution in HCW-2 cells, an apoptosis-resistant clone of human HL-60 cells. In HL-60, about 50% of total CL is distributed in the outer leaflet of mitochondrial inner membrane, while in HCW-2 a significantly higher amount of CL (about 65%) is in that site. In basal conditions, HSW-2 cells also show a reduced mitochondrial membrane potential even if they are able to proliferate as the parental line. Taking into account the complex functions that CL plays in the regulation of mitochondrial activity, it is likely that HCW-2 could produce ATP utilizing more glycolytic pathways rather than mitochondrial respiratory chain.

Effect of triiodothyronine on reactive oxygen species generation by leukocytes, indices of oxidative damage, and antioxidant reserve

We have examined the effect of short-term triiodothyronine (T3) administration on reactive oxygen species (ROS) generation by leukocytes in 9 euthyroid subjects. At a dose of 60 microg/d orally for 7 days, T3 induced a significant increase in ROS generation by mononuclear cells (MNCs) from 183 +/- 102 mV at baseline to 313 +/- 111 mV on the seventh day (P < .02), and by polymorphonuclear leukocytes (PMNLs) from 195 +/- 94 mV at baseline to 302 +/- 104 mV on the seventh day (P < .02). There was also a significant increase in meta-tyrosine (P < .001) and ortho-tyrosine (P < .001), known indices of oxidative damage to proteins and amino acids. However, there was no increase in plasma thiobarbituric acid-reactive substances (TBARS), an index of oxidative damage to lipids, and in the level of carbonylated proteins, a less sensitive index to assess protein oxidation. There was no decrease in the level of antioxidants such as alpha-tocopherol, vitamin A, beta-carotene, lycopene, and lutein/zeaxanthin. The stimulatory effect on ROS generation may reflect a generalized increase in metabolic activity or may be a specific effect on NADPH oxidase in leukocyte membranes. The absence of a significant change in TBARS, carbonylated proteins, alpha-tocopherol, vitamin A, beta-carotene, lycopene, and lutein/zeaxanthin may reflect the short duration of the increased ROS load.

Mitochondrial protonophoric activity induced by a thyromimetic fatty acid analogue

Calcium-dependent uncoupling of liver mitochondrial oxidative phosphorylation by a non-metabolizable long chain fatty acyl analogue was compared with uncoupling induced by in vivo thyroid hormone treatment. beta,beta'-Methyl-substituted hexadecane alpha, omega-dioic acid (Medica 16) is reported here to induce a saturable 20-30% decrease in liver mitochondrial DeltaPsi, DeltapH and protonmotive force which proceeds in the presence of added Ca(2+) to cyclosporin A-sensitive mitochondrial permeabilization. Ca(2+)-dependent uncoupling by Medica 16 was accompanied by atractylate-enhanced, bongkrekic-inhibited activation of mitochondrial Ca(2+) efflux. The direct mitochondrial effect exerted in vitro by Medica 16 is similar to that induced by in vivo thyroid hormone treatment. Hence, the thyromimetic protonophoric activity of Medica 16 and the uncoupling activity of TH converge onto components of the mitochondrial permeabilization transition pore.

Action of thyroid hormones at the cellular level: the mitochondrial target

Thyroid hormones exert profound effects on the energy metabolism. An inspection of the early and more recent literature shows that several targets at the cellular level have been identified. Since their effects on the nuclear signalling pathway have already been well-defined and extensively reviewed, this article focuses on the regulation of mitochondrial activity by thyroid hormones. Mitochondria, by virtue of their biochemical functions, are a natural candidate as a direct target for the calorigenic effects of thyroid hormones. To judge from results coming from various laboratories, it is quite conceivable that mitochondrial activities are regulated both directly and indirectly. Not only triiodo-L-thyronine, but also diiodothyronines are active in regulating the energy metabolism. They influence the resting metabolism in rats with 3,5-diiodo-L-thyronine seeming to show a clearer effect.

Mitochondrial physiology and pathology; concepts of programmed death of organelles, cells and organisms

The review summarizes the present state of our knowledge concerning alternative functions of mitochondria, namely energy conservation in forms of protonic potential and ATP, thermoregulatory energy dissipation as heat, production of useful substances, decomposition of harmful substances, control of cellular processes. The recent progress in understanding of some mitochondrion-linked pathologies is described. The role of reactive oxygen species in these processes is stressed. Possible mechanisms of programmed death of mitochondrion (mitoptosis), cell (apoptosis) and organism (phenoptosis) are considered. A concept is put forward assuming that mitoptosis is involved in some types of apoptosis whereas apoptosis can be a part of a phenoptotic cascade. It is hypothesized that septic shock, as well as the stress-induced brain and heart ischemic diseases and cancer, exemplify mechanisms of phenoptosis purifying population, community of organisms or kin from dangerous or useless individuals.

Expression of uncoupling protein-3 and mitochondrial activity in the transition from hypothyroid to hyperthyroid state in rat skeletal muscle

We sought a correlation between rat skeletal muscle triiodothyronine (T3)-mediated regulation of uncoupling protein-3 (UCP3) expression and mitochondrial activity. UCP3 mRNA expression increased strongly during the hypothyroid-hyperthyroid transition. The rank order of mitochondrial State 3 and State 4 respiration rates was hypothyroid < euthyroid < hyperthyroid. The State 4 increase may have been due to the increased UCP3 expression, as the proton leak kinetic was stimulated in the hypothyroid-hyperthyroid transition and a good correlation exists between the State 4 and UCP3 mRNA level. As a significant proportion of an organism's resting oxygen consumption is dedicated to opposing the proton leak, skeletal muscle mitochondrial UCP3 may mediate part of T3's effect on energy metabolism.

Thermoregulatory uncoupling in heart muscle mitochondria: involvement of the ATP/ADP antiporter and uncoupling protein

Possible involvement of the ATP/ADP antiporter and uncoupling protein (UCP) in thermoregulatory uncoupling of oxidative phosphorylation in heart muscle has been studied. To this end, effects of carboxyatractylate (cAtr) and GDP, specific inhibitors of the antiporter and UCP, on the membrane potential of the oligomycin-treated mitochondria from cold-exposed (6 degrees C, 48 h) and control rats have been measured. It is found that cAtr increases the membrane potential level in both cold-exposed and non-exposed groups, the effect being strongly enhanced by cooling. As for GDP, it is effective only in mitochondria from the cold-exposed rats. In these mitochondria, the coupling effect of GDP is smaller than that of cAtr. CDP, which does not interact with UCP, is without any influence on membrane potential. The cold exposure is found to increase the uncoupling efficiency of added natural (palmitate) or artificial (SF6847) uncouplers, the increase being cAtr- and GDP-sensitive in the case of palmitate. The fatty acid-free bovine serum albumin enhances delta psi in both cold-exposed and control groups, the effect being much larger in the former case. It is concluded that in heart muscle mitochondria the ATP/ADP antiporter is responsible for the 'mild uncoupling' under normal conditions and for major portion of the thermoregulatory uncoupling in the cold whereas the rest of thermoregulatory uncoupling is served by UCP (presumably by UCP2 since the UCP2 mRNA level is shown to strongly increase in rat heart muscle under the cold exposure conditions used).