Energy metabolism and NAD-NADH redox state in brain slices in response to glutamate exposure and ischemia

In vitro culture of bovine fibroblasts using select serum-free media supplemented with Chlorella vulgaris extract

Standard cell culture practices require the addition of animal-derived serum to culture media to achieve adequate cell growth. Typically, 5-10% by volume of fetal bovine serum (FBS) is used, which accounts for a vast majority of the media cost while also imposing environmental and ethical concerns associated with the use of animal serum. Here we tested the efficacy of culturing cells by replacing serum in the media with algae extract and select additives. Using LC-MS, we compared molecular signatures of FBS to Chlorella algae extracts and identified NAD(H)/NADP(H) as common and relatively abundant features in their characteristic profiles. Bovine fibroblasts, cultured in serum-free media supplemented with C. vulgaris extract and just two growth factors plus insulin, showed significant growth with enhanced viability compared to control cells cultured without serum, albeit still lower than that of controls cultured with 10% FBS. Moreover, C. vulgaris extract enhanced cell viability beyond that of cells cultured with the two growth factors and insulin alone. These results suggest that key components in serum which are essential for cell growth may also be present in C. vulgaris extract, demonstrating that it may be used at least as a partial alternative to serum for cell culture applications.

Redox signalling in cardiovascular disease

Oxidative stress has almost universally and unequivocally been implicated in the pathogenesis of all major diseases, including those of the cardiovascular system. Oxidative stress in cells and cardiovascular biology was once considered only in terms of injury, disease and dysfunction. However, it is now appreciated that oxidants are also produced in healthy tissues, and they function as signalling molecules transmitting information throughout the cell. Conversely, when cells move to a more reduced state, as can occur when oxygen is limiting, this can also result in alterations in the function of biomolecules and subsequently cells. At the centre of this 'redox signalling' are oxidoreductive chemical reactions involving oxidants or reductants post translationally modifying proteins. These structural alterations allow changes in cellular redox state to be coupled to alterations in cell function. In this review, we consider aspects of redox signalling in the cardiovascular system, focusing on the molecular basis of redox sensing by proteins and the array of post-translational oxidative modifications that can occur. In addition, we discuss studies utilising proteomic methods to identify redox-sensitive cardiac proteins, as well as those using this technology more broadly to assess redox signalling in cardiovascular disease.

Glutamate-induced differential mitochondrial response in young and adult rats

Excitatory amino acid glutamate is involved in neurotransmission in the nervous system but it becomes a potent neurotoxin under variety of conditions. However, the molecular mechanism of excitotoxicity is not known completely. We have studied the influence of glutamate on intracellular calcium and mitochondrial functions in cortical slices from young and adult rats. The slices from both the age groups exhibited comparable intracellular calcium changes upon glutamate stimulation. Glutamate treatment caused a decrease in adenosine 5'-diphosphate/adenosine 5'-triphosphate (ADP/ATP) and an increase in nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide reduced form (NAD/NADH) ratio in both the age groups but the magnitude and the nature of temporal change was different. Glutamate-induced decrease in ATP/ADP and increase in NAD/NADH ratio was significantly higher in slices from the adult as compared to the young rats. The slices from young rats elicited slightly higher mitochondrial depolarization than adult rats. However, the formation of reactive oxygen species (ROS) and lactate dehydrogenase (LDH) release were significantly higher in adult rats as compared to young rats. Glutamate-induced mitochondrial depolarization, ROS formation and LDH release were highly dependent on the presence of Ca(2+) in the extracellular medium. The treatment of slices with mitochondrial inhibitors rotenone and oligomycin inhibited ROS formation and LDH release substantially. Our results suggest that the glutamate-induced increase in intracellular calcium is not the only factor responsible for neuronal cell death but the mitochondrial functions could be crucial in excitotoxicity.

Calcium sequestering ability of mitochondria modulates influx of calcium through glutamate receptor channel

The excitotoxicity of glutamate is believed to be mediated by sustained increase in the cytosolic Ca2+ concentration. Mitochondria play a vital role in buffering the cytosolic calcium overload in stimulated neurons. Here we have studied the glutamate induced Ca2+ signals in cortical brain slices under physiological conditions and the conditions that modify the mitochondrial functions. Exposure of slices to glutamate caused a rapid increase in [Ca2+]i followed by a slow and persistently rising phase. The rapid increase in [Ca2+]i was mainly due to influx of Ca2+ through the N-methyl-D-aspartate (NMDA) receptor channels. Glutamate stimulation in the absence of Ca2+ in the extracellular medium elicited a small transient rise in [Ca2+]i which can be attributed to the mobilization of Ca2+ from IP3 sensitive endoplasmic reticulum pools consequent to activation of metabotropic glutamate receptors. The glutamate induced Ca2+ influx was accompanied by depolarization of the mitochondrial membrane, which was inhibited by ruthenium red, the blocker of mitochondrial Ca2+ uniporter. These results imply that mitochondria sequester the Ca2+ loaded into the cytosol by glutamate stimulation. Persistent depolarization of mitochondrial membrane observed in presence of extracellular Ca2+ caused permeability transition and released the sequestered Ca2+ which is manifested as slow rise in [Ca2+]i. Protonophore carbonyl cyanide m-chlorophenyl-hydrazone (CCCP) depolarized the mitochondrial membrane and enhanced the glutamate induced [Ca2+]i response. Contrary to this, treatment of slices with mitochondrial inhibitor oligomycin or ruthenium red markedly reduced the [Ca2+]i response. Combined treatment with oligomycin and rotenone further diminished the [Ca2+]i response and also abolished the CCCP mediated rise in [Ca2+]i. However, rotenone alone had no effect on glutamate induced [Ca2+]i response. These changes in glutamate-induced [Ca2+]i response could not be explained on the basis of deficient mitochondrial Ca2+ sequestration or ATP dependent Ca2+ buffering. The mitochondrial inhibitors reduced the cellular ATP/ADP ratio, however, this would have restrained the ATP dependent Ca2+ buffering processes leading to elevation of [Ca2+]i. In contrast our results showed repression of Ca2+ signal except in case of CCCP which drastically reduced the ATP/ADP ratio. It was inferred that, under the conditions that hamper the Ca2+ sequestering ability of mitochondria, the glutamate induced Ca2+ influx could be impeded. To validate this, influx of Mn2+ through ionotropic glutamate receptor channel was monitored by measuring the quenching of Fura-2 fluorescence. Treatment of slices with oligomycin and rotenone prior to glutamate exposure conspicuously reduced the rate of glutamate induced fluorescence quenching as compared to untreated slices. Thus our data establish that the functional status of mitochondria can modify the activity of ionotropic glutamate receptor and suggest that blockade of mitochondrial Ca2+ sequestration may desensitize the NMDA receptor operated channel.