Role of mitochondria in the immune response to cancer: a central role for Ca2+

Biocompatibility and immunostimulatory properties of fish collagen and shrimp chitosan towards peripheral blood mononuclear cells (PBMCs)

Several naturally occurring biopolymers are commercially produced from livestock and farmed animals processing wastes, including aquatic organisms. These wastes are considered valuable coproducts of fishery processing industry, from which biopolymers may be recovered and exploited for their bioactive potential. The aim of this work was to prepare polymeric films from collagen and chitosan solutions, extracted from fishery discards, and investigate the cytotoxicity and immunomodulatory activity towards human peripheral blood mononuclear cells (PBMCs). PBMCs were isolated from healthy donors and treated with Chitosan, Collagen, Chitosan+Collagen solutions and Chitosan+Collagen film in order to measure the changes in cell viability, cytosolic calcium concentration ([Ca²⁺]cyt), mitochondrial membrane potential (ΔΨm), reactive oxygen species (ROS) levels, differentiation and activation of T CD8⁺ and CD4⁺ lymphocytes, and cytokine production. Results showed that collagen and chitosan preparations did not show cytotoxic effect, while cellular IL-6, IL-10, and TNF-α release was observed. Chitosan and collagen were able to promote non-cytotoxic PBMCs activation through cytosolic and mitochondrial ROS production. There was a noteworthy phenotyping of lymphocytes T CD8⁺ and CD4⁺ counting and an increase of [Ca²⁺] cyt and ΔΨm levels. These results suggest that chitosan/collagen-based biomaterials produce immunostimulatory effects on PBMC with potential to biomedical approaches.

Mitotherapy: Unraveling a Promising Treatment for Disorders of the Central Nervous System and Other Systemic Conditions

Mitochondria are key players of aerobic respiration and the production of adenosine triphosphate and constitute the energetic core of eukaryotic cells. Furthermore, cells rely upon mitochondria homeostasis, the disruption of which is reported in pathological processes such as liver hepatotoxicity, cancer, muscular dystrophy, chronic inflammation, as well as in neurological conditions including Alzheimer’s disease, schizophrenia, depression, ischemia and glaucoma. In addition to the well-known spontaneous cell-to-cell transfer of mitochondria, a therapeutic potential of the transplant of isolated, metabolically active mitochondria has been demonstrated in several in vitro and in vivo experimental models of disease. This review explores the striking outcomes achieved by mitotherapy thus far, and the most relevant underlying data regarding isolated mitochondria transplantation, including mechanisms of mitochondria intake, the balance between administration and therapy effectiveness, the relevance of mitochondrial source and purity and the mechanisms by which mitotherapy is gaining ground as a promising therapeutic approach.

Lignins isolated from Prickly pear cladodes of the species Opuntia fícus-indica (Linnaeus) Miller and Opuntia cochenillifera (Linnaeus) Miller induces mice splenocytes activation, proliferation and cytokines production

Opuntia fícus-indica and Opuntia cochenillifera are species of Cactaceae, found in the arid regions of the planet. They present water, cellulose, hemicellulose, pectins, extractives, ashes and lignins. Here we aimed to study the immunomodulatory action of lignins from these two species against mice splenocytes, since no study for this purpose has yet been reported. The antioxidant activities of these lignins were evaluated by the DPPH, ABTS, NO assays and total antioxidant activity. Cytotoxicity was evaluated through Annexin V-FITC and propidium iodide-PE probs and cell proliferation was determined by CFSE. Immunomodulation studies with Opuntia lignins obtained were performed through investigation of ROS levels, cytosolic calcium release, changes on mitochondrial membrane potential, cytokine production and NO release. Results showed that Opuntia cochenillifera lignin presented more phenolic amount and antioxidant activities than Opuntia ficius-indica. Both lignins showed high cell viability (>96%) and cell proliferation. Activation signal was observed for both lignins with increase of ROS and cytosolic calcium levels, and changes in mitochondrial membrane potential. In addition, lignins induced high TNF-α, IL-6 and IL-10 production and reduced NO release. Therefore, these lignins present great potential to be used as molecules with a proinflammatory profile, being shown as a promising therapeutic agent.

Activation of the mitochondrial ATP-sensitive K+ channel reduces apoptosis of spleen mononuclear cells induced by hyperlipidemia

Background

We have previously demonstrated that increased rates of superoxide generation by extra-mitochondrial enzymes induce the activation of the mitochondrial ATP-sensitive potassium channel (mitoK_ATP) in the livers of hypertriglyceridemic (HTG) mice. The resulting mild uncoupling mediated by mitoK_ATP protects mitochondria against oxidative damage. In this study, we investigate whether immune cells from HTG mice also present increased mitoK_ATP activity and evaluate the influence of this trait on cell redox state and viability.

Methods

Oxygen consumption (Clark-type electrode), reactive oxygen species production (dihydroethidium and H2-DCF-DA probes) and cell death (annexin V, cytocrome c release and Trypan blue exclusion) were determined in spleen mononuclear cells.

Results

HTG mice mononuclear cells displayed increased mitoK_ATP activity, as evidenced by higher resting respiration rates that were sensitive to mitoK_ATP antagonists. Whole cell superoxide production and apoptosis rates were increased in HTG cells. Inhibition of mitoK_ATP further increased the production of reactive oxygen species and apoptosis in these cells. Incubation with HTG serum induced apoptosis more strongly in WT cells than in HTG mononuclear cells. Cytochrome c release into the cytosol and caspase 8 activity were both increased in HTG cells, indicating that cell death signaling starts upstream of the mitochondria but does involve this organelle. Accordingly, a reduced number of blood circulating lymphocytes was found in HTG mice.

Conclusions

These results demonstrate that spleen mononuclear cells from hyperlipidemic mice have more active mitoK_ATP channels, which downregulate mitochondrial superoxide generation. The increased apoptosis rate observed in these cells is exacerbated by closing the mitoK_ATP channels. Thus, mitoK_ATP opening acts as a protective mechanism that reduces cell death induced by hyperlipidemia.

Mitochondria as oxidative signaling organelles in T-cell activation: physiological role and pathological implications

Early scientific reports limited the cell biological role of reactive oxygen species (ROS) to the cause of pathological damage. However, extensive research performed over the last decade led to a wide recognition of intracellular oxidative/redox signaling as a crucial mechanism of homeostatic regulation. Amongst different cellular processes known to be influenced by redox signaling, T-cell activation is one of the most established. Numerous studies reported an indispensible role for ROS as modulators of T-cell receptor-induced transcription. Nevertheless, mechanistic details regarding signaling pathways triggered by ROS are far from being delineated. The nature and interplay between enzymatic sources involved in the generation of "oxidative signals" are also a matter of ongoing research. In particular, active participation of the mitochondrial respiratory chain as ROS producer constitutes an intriguing issue with various implications for bioenergetics of activated T cells as well as for T-cell-mediated pathologies. The aim of the current review is to address these interesting concepts.

Reduction in generation of reactive oxygen species and endothelial dysfunction during postprandial state

BACKGROUND AND AIMS

To characterise changes in generation of cellular reactive oxygen species (ROS) in healthy males during the postprandial state, and to analyse the influence of the postprandial state on endothelial ROS generation and endothelial dysfunction.

METHODS AND RESULTS

Seventeen healthy subjects were recruited. Blood samples were collected in the fasting state and 2, 4, 6 and 8h after liquid-meal intake (composition: 25% fat, 55% dextromaltose and 14% protein), providing 40 gfat m(-2) body surface. Plasma lipids, apolipoproteins, glucose and insulin were measured during this period. Peripheral blood mononuclear cells (PBMCs) were isolated by density-gradient centrifugation. The influence of postprandial state on intracellular ROS generation was measured by two different methods in PBMCs and in a human immortalised endothelial cell line (ECV 304). Artery flow-mediated vasodilation (FMD) was used to evaluate the endothelial function, and oxygen consumption by PBMCs was measured. Reduced ROS generation was observed in all methods and cells during the postprandial period. FMD was impaired 8h after meal intake (23±6 vs. 13±2, P<0.05 vs. baseline). The consumption of oxygen was reduced in PBMCs (-14% into 2h, P<0.05 vs. baseline and -27% after 4h, P<0.01 vs. baseline). ROS generation was correlated with plasma lipids, insulin, apolipoproteins and oxygen consumption.

CONCLUSIONS

In contrast to the previously reported elevation of postprandial oxidative stress, this study shows reduced ROS generation in PBMCs and in ECV 304. Data obtained in both cellular models suggest the existence of a protective response against plasma postprandial oxidative stress.

Rhizoma coptidis and berberine-induced activation of murine microglia N9 cells

AIMS OF THE STUDY

To investigate the effect of water extract of Rhizoma coptidis (WEC) and berberine on the activation of murine microglia N9 cells and corresponding mechanism related to mitochondria.

MATERIALS AND METHODS

Phagocytic activity of murine microglia N9 cells was measured by neutral red staining method after the cells were treated with various concentrations of WEC and alkaloids for 24h. Flow cytometric analysis was performed to determine the level of intracellular ROS, Ca(2+), and mitochondrial transmembrane potential (Delta psi) after 87 microg/ml of WEC and 12.4 microg/ml of berberine treatment. Global changes of gene expression in WEC- and berberine-treated N9 cells were measured using cDNA microarray.

RESULTS

WEC and berberine, but not palmatine and jatrorrhizine, enhanced phagocytic activity of murine N9 cells in a dose-dependent manner. Both of WEC and berberine stimulated free radical generation, enhanced mitochondrial Delta psi and induced gene expression of Ndufab1, Cox6a2 and Atp5a1. However, a more significant phagocytic effect was observed for WEC. WEC, but not berberine, increased intracellular Ca(2+) concentration. The gene expression of Atp5c1 was selectively up-regulated by WEC, while three genes of Uqcrq, Cox8b, and Atp5g2 were induced by berberine.

CONCLUSIONS

WEC and berberine activated murine microglia N9 cells by the regulation of mitochondrial function and mitochondria-related signal molecules. The action of WEC is stronger than that of berberine, indicating that the effect of WEC is ascribed partially, but not totally, to berberine.

High susceptibility of activated lymphocytes to oxidative stress-induced cell death

The present study provides evidence that activated spleen lymphocytes from Walker 256 tumor bearing rats are more susceptible than controls to tert-butyl hydroperoxide (t-BOOH)-induced necrotic cell death in vitro. The iron chelator and antioxidant deferoxamine, the intracellular Ca2+ chelator BAPTA, the L-type Ca2+ channel antagonist nifedipine or the mitochondrial permeability transition inhibitor cyclosporin A, but not the calcineurin inhibitor FK-506, render control and activated lymphocytes equally resistant to the toxic effects of t-BOOH. Incubation of activated lymphocytes in the presence of t-BOOH resulted in a cyclosporin A-sensitive decrease in mitochondrial membrane potential. These results indicate that the higher cytosolic Ca2+ level in activated lymphocytes increases their susceptibility to oxidative stress-induced cell death in a mechanism involving the participation of mitochondrial permeability transition.

Oxidative stress in hypercholesterolemic LDL (low-density lipoprotein) receptor knockout mice is associated with low content of mitochondrial NADP-linked substrates and is partially reversed by citrate replacement

We have previously proposed that hypercholesterolemic LDL receptor knockout (k/o) mice mitochondria possess a lower antioxidant capacity due to a large consumption of reducing equivalents from NADPH to sustain high rates of lipogenesis. In this work, we tested the hypothesis that this k/o mice mitochondrial oxidative stress results from the depletion of NADPH-linked substrates. In addition, the oxidative stress was further characterized by showing a lower mitochondrial GSH/GSSG ratio and a higher liver content of protein carbonyls as compared to controls. The activity of the antioxidant enzyme system glutathione reductase/peroxidase did not differ in k/o and control mitochondria. The faster spontaneous oxidation of endogenous NADPH in the k/o mitochondria was prevented by the addition of exogenous catalase, indicating that this oxidation is mediated by mitochondrially generated H(2)O(2). The higher rate of H(2)O(2) production was also prevented by the addition of exogenous isocitrate that maintains NADP fully reduced. The hypothesis that high rates of lipogenesis in the k/o cells decrease mitochondrial NADPH/NADP(+) ratio due to consumption of NADPH-linked substrates was supported by two findings: (i) oxygen consumption supported by endogenous NAD(P)H-linked substrates was slower in k/o than in control mitochondria, but was similar in the presence of exogenous isocitrate; (ii) in vivo treatment of k/o mice with sodium citrate/citric acid drinking solution for 2 weeks partially restored both the rate of oxygen consumption supported by NAD(P)H-linked substrates and the mitochondrial capacity to sustain reduced NADPH. In conclusion, the data demonstrate that the mitochondrial oxidative stress in hypercholesterolemic LDL receptor knockout mice is the result of a low content of mitochondrial NADPH-linked substrates in the intact animal that can be, at least in part, replenished by oral administration of citrate.

High Bcl-2/Bax ratio in Walker tumor cells protects mitochondria but does not prevent H2O2-induced apoptosis via calcineurin pathways

It has been previously shown that Walker 256 tumor cells express a high content of the anti-apoptotic protein Bcl-2 which protects mitochondria against the damaging effects of Ca(2+). In the present study, we analyze H(2)O(2)-induced apoptotic death in two different types of tumor cells: Walker 256 and SCC-25. Treatment with H(2)O(2) (4mM) increased reactive oxygen species generation and the concentration of cytosolic free Ca(2+). These alterations preceded apoptosis in both cell lines. In Walker cells, which show a high Bcl-2/Bax ratio, apoptosis was dependent on calcineurin activation and independent of changes in mitochondrial membrane potential (DeltaPsi(m)), as well as cytochrome c release. In contrast, in SCC-25 cells, which show a lower Bcl-2/Bax ratio, apoptosis was preceded by a decrease in DeltaPsi(m), mitochondrial permeability transition, and cytochrome c release. Caspase-3 activation occurred in both cell lines. The data suggest that although the high Bcl-2/Bax ratio protected the mitochondria of Walker cells from oxidative stress, it was not sufficient to prevent apoptosis through calcineurin pathways.

Verapamil-sensitive Ca2+ channel regulation of Th1-type proliferation of splenic lymphocytes induced by Walker 256 tumor development in rats

Recently, we demonstrated that verapamil, an L-type Ca2+ channel blocker, inhibits the activation of splenic lymphocytes during Walker 256 ascitic tumor development in adult rats. In the present study we have analyzed the changes in spleen size, splenic lymphocyte proliferation, white pulp organization and relative size as well as food intake, and levels of blood haemoglobin in Walker 256 tumor bearing rats. These rats displayed a spleen enlargement associated with a significant increase in white pulp area and TCD8+ lymphocyte proliferation. Levels of interferon-gamma, but not of interleukin-10, were elevated in tumor bearing rats, indicating a Th1-type immune response. These manifestations were accompanied by reduced food intake and anaemia. Treatment of tumor bearing rats with verapamil avoided spleen enlargement and increased expression of cytokines, as well as the splenic TCD8+ lymphocyte proliferation. In addition, verapamil treatment promoted an exacerbation of the anorexia and anaemia caused by Walker tumor development. No such effect was observed in control rats treated with verapamil. Taken together, these findings suggest that verapamil inhibits the immune response to cancer, resulting in an increase of the systemic effects induced by Walker 256 tumor.