The cellular energy crisis: mitochondria and cell death

Comparative transcriptome analysis reveals potential fruiting body formation mechanisms in Morchella importuna

Morchella importuna has been artificially cultivated, but stable production remains difficult because its mechanisms of fruiting body formation are unclear. To investigate the fruiting body formation mechanisms, we sequenced the transcriptomes of Morchella importuna at the mycelial and young fruiting body stages. Among the 12,561 differentially expressed genes (DEGs), 9215 were upregulated, and 3346 were downregulated. DEG enrichment analysis showed that these genes were enriched in the "generation of precursor metabolites and energy", "carbohydrate catabolic process", and "oxidoreductase activity" Gene Ontology (GO) functional categories. Enzyme activity assay results indicated that the activity levels of CAZymes (carbohydrate-active enzymes), oxidoreductases (SOD (superoxide dismutase), CAT (catalase)) and mitochondrial complex (complex I, II, III) proteins were significantly increased from the mycelial stage to the young fruiting body stage. In addition, the genes encoding CAZymes, mitochondrial proteins, oxidoreductases and heat shock proteins had higher expression levels in the young fruiting body stage than in the mycelial stage, and the qRT-PCR results showed similar trends to the RNA-Seq results. In summary, these results suggest that carbohydrate catabolism and energy metabolism are significantly enhanced in the young fruiting body stage and that growth environment temperature changes affect the formation of fruiting bodies.

Boldine Supplementation Regulates Mitochondrial Function and Oxidative Stress in a Rat Model of Hepatotoxicity

Background: The xenobiotics-induced liver injury is a clinical complication. Hence, finding new hepatoprotective strategies has clinical value. Oxidative stress and its subsequent complications are major mechanisms involved in xenobiotics-induced hepatotoxicity. Boldine is one of the most potent antioxidant molecules widely investigated for its protective properties in different experimental models. In the current study, the hepatoprotective properties of boldine and its potential mechanisms of hepatoprotection have been investigated. Methods: Rats received thioacetamide (TAA; 200 mg/kg, i.p) as a model of acute liver injury. Boldine (5, 10, 1nd 20 mg/kg; 24 hours intervals; oral) was administered as the hepatoprotective agent. Results: Liver injury was evident in TAA-treated animals (48 hours after TAA exposure) as a severe increase in serum level of liver injury biomarkers and histopathological alterations. Moreover, markers of oxidative stress were increased in liver tissue of TAA-treated rats. Assessment of mitochondrial indices of functionality revealed a significant decrease in mitochondrial dehydrogenases activity, the collapse of mitochondrial membrane potential, mitochondrial swelling and depletion of ATP content. It was found that boldine supplementation mitigated liver tissue markers of oxidative stress and improved mitochondrial indices of functionality in TAA-treated animals. Conclusion: The hepatoprotective properties of boldine might primarily rely on antioxidant and mitochondria protecting effects of this alkaloid.

Metabolic Enhancer Piracetam Attenuates the Translocation of Mitochondrion-Specific Proteins of Caspase-Independent Pathway, Poly [ADP-Ribose] Polymerase 1 Up-regulation and Oxidative DNA Fragmentation

Piracetam, a nootropic drug, has been clinically used for decades; however, its mechanism of action still remains enigmatic. The present study was undertaken to evaluate the role of mitochondrion-specific factors of caspase-independent pathway like apoptotic-inducing factor (AIF) and endonuclease-G (endo-G) in piracetam-induced neuroprotection. N2A cells treated with lipopolysaccharide (LPS) exhibited significant cytotoxicity, impaired mitochondrial activity, and reactive oxygen species generation which was significantly attenuated with piracetam co-treatment. Cells co-treated with LPS and piracetam exhibited significant uptake of piracetam in comparison to only piracetam-treated cells as estimated by liquid chromatography-mass spectrometry (LC-MSMS). LPS treatment caused significant translocation of AIF and endonuclease-G in neuronal N2A cells which were significantly attenuated with piracetam co-treatment. Significant over-expression of proinflammatory cytokines was also observed after treatment of LPS to cells which was inhibited with piracetam co-treatment demonstrating its anti-inflammatory property. LPS-treated cells exhibited significant oxidative DNA fragmentation and poly [ADP-ribose] polymerase-1 (PARP-1) up-regulation in nucleus, both of which were attenuated with piracetam treatment. Antioxidant melatonin but not z-VAD offered the inhibited LPS-induced DNA fragmentation indicating the involvement of oxidative DNA fragmentation. Further, we did not observe the altered caspase-3 level after LPS treatment initially while at a later time point, significantly augmented level of caspase-3 was observed which was not inhibited with piracetam treatment. In total, our findings indicate the interference of piracetam in mitochondrion-mediated caspase-independent pathway, as well as its anti-inflammatory and antioxidative properties. Graphical Abstract Graphical abstract indicating the novel interference of metabolic enhancer piracetam (P) in neuronal death mechanisms.

Possible role of mitochondrial dysfunction in central neurodegeneration of ovariectomized rats

In the present study, ovariectomized Sprague-Dawley rats were used to mimic the pathological changes of post-menopausal females with genistein and estradiol benzoate (EB) as substitutes for endogenous estradiol. Measurements of hippocampal ATP content, mitochondrial ATP content and the rate of mitochondrial ATP synthesis in the hippocampus indicated that after ovariectomy, brain energy metabolism of the rats presented a transient change in hippocampal ATP content which was significant from the 6th to the 8th day after ovariectomy. The change on the 6th day was the most noteworthy. Mitochondrial ATP content and the rate of mitochondrial ATP synthesis of the hippocampus were also lowered. However, after using EB or genistein, the three indicators returned to normal. It is suggested that mitochondrial dysfunction may play a key role in Alzheimer's disease (AD) of the post-menopausal female, and may serve as the target for endogenous estrogen and exogenous phytoestrogen. In addition, genistein, which possesses the properties of estrogen but not its side effects such as carcinogenicity, could reverse the bioenergetic defects of ovariectomized rats and perhaps be used as a substitute for estradiol to prevent or treat central neurodegeneration in post-menopausal women.

Are mitochondria critical in the pathogenesis of Alzheimer's disease?

This review summarizes recent findings that suggest a causal connection between mitochondrial abnormalities and sporadic Alzheimer's disease (AD). Genetic causes of AD are known only for a small proportion of familial AD patients, but for a majority of sporadic AD patients, genetic causal factors are still unknown. Currently, there are no early detectable biomarkers for sporadic AD, and there is a lack of understanding of the pathophysiology of the disease. Findings from recent genetic studies of AD pathogenesis suggest that mitochondrial defects may play an important role in sporadic AD progression, and that mitochondrial abnormalities and oxidative damage may play a significant role in the progression of familial AD. Findings from biochemical studies, in vitro studies, gene expression studies, and animal model studies of AD are reviewed, and the possible contribution of mitochondrial mutations to late-onset sporadic AD is discussed.

The role of the mitochondrion in trauma and shock

The mitochondrion of the eukaryotic cell is well known as a "power plant" whose energy is made available via the high-energy phosphate bonds of ATP. This indispensable and superbly adapted organelle appears to have originated as an endosymbiotic bacterium rather than as a eukaryotic creation per se. However, under the dangerous conditions of trauma and shock, the mitochondrion can become destabilized and harm its host cell in a variety of ways. These contrary traits may be, in part, vestiges from the bacterial origins of mitochondria. The mitochondrion can respond to the stress of trauma and shock by opening pores that leak contents into the host cell's cytoplasm, an event that can trigger programmed cell death or necrosis. In addition, the enormous oxygen consumption by mitochondria presents a two-edged sword in that a deranged mitochondrion can produce reactive oxygen species that damage genes and gene products, inflicting considerable harm to the mitochondrion and its host cell. However, although trauma and shock can cause the mitochondrion to wreak havoc in many ways, an adjuvant intervention with exogenous ATP-MgCl2 after trauma and shock appears useful for reducing cell and organ damage under those conditions.

Actions of thermal stress in two-cell bovine embryos: oxygen metabolism, glutathione and ATP content, and the time-course of development

The mechanism by which heat shock disrupts development of the two-cell bovine embryo was examined. The reduction in the proportion of embryos that became blastocysts caused by heat shock was not exacerbated when embryos were cultured in air (20.95% O(2)) as compared with 5% O(2). In addition, heat shock did not reduce embryonic content of glutathione, cause a significant alteration in oxygen consumption, or change embryonic ATP content. When embryos were heat-shocked at the two-cell stage and allowed to continue development until 72 h post insemination, heat-shocked embryos had fewer total nuclei and a higher percentage of them were condensed. Moreover, embryos became blocked in development at the eight-cell stage. The lack of effect of the oxygen environment on the survival of embryos exposed to heat shock, as well as the unchanged content of glutathione, suggest that free radical production is not a major cause for the inhibition in development caused by heat shock at the two-cell stage. In addition, heat shock appears to have no immediate effect on oxidative phosphorylation since no differences in ATP content were observed. Finally, the finding that heat shock causes a block to development at the eight-cell stage implies that previously reported mitochondrial damage caused by heat shock or other heat shock-induced alterations in cellular physiology render the embryo unable to proceed past the eight-cell stage.