Caspase-2 and the oxidative stress response

Indomethacin can induce cell death in rat gastric parietal cells through alteration of some apoptosis- and autophagy-associated molecules

In clinical medicine, indomethacin (IND, a non-steroidal anti-inflammatory drug) is used variously in the treatment of severe osteoarthritis, rheumatoid arthritis, gouty arthritis or ankylosing spondylitis. A common complication found alongside the therapeutic characteristics is gastric mucosal damage. This complication is mediated through apoptosis and autophagy of the gastrointestinal mucosal epithelium. Apoptosis and autophagy are critical homeostatic pathways catalysed by caspases downstream of the gastrointestinal mucosal epithelial injury. Both act through molecular signalling pathways characterized by the initiation, mediation, execution and regulation of the cell regulatory cycle. In this study we hypothesized that dysregulated apoptosis and autophagy are associated with IND-induced gastric damage. We examined the spectra of in vivo experimental gastric ulcers in male Sprague-Dawley rats through gastric gavage of IND. Following an 18-hour fast, IND was administered to experimental rats. They were sacrificed at 3-, 6- and 12-hour intervals. Parietal cells (H⁺ , K⁺ -ATPase β-subunit assay) and apoptosis (TUNEL assay) were determined. The expression of apoptosis-signalling caspase (caspases 3, 8, 9 and 12), DNA damage (anti-phospho-histone H2A.X) and autophagy (MAP-LC3, LAMP-1 and cathepsin B)-related molecules in gastric mucosal cells was examined. The administration of IND was associated with gastric mucosal erosions and ulcerations mainly involving the gastric parietal cells (PCs) of the isthmic and upper neck regions and a time-dependent gradual increase in the number of apoptotic PCs with the induction of both apoptotic (upregulation of caspases 3 and 8) cell death and autophagic (MAP-LC3-II, LAMP-1 and cathepsin B) cell death. Autophagy induced by fasting and IND 3 hours initially prompted the degradation of caspase 8. After 6 and 12 hours, damping down of autophagic activity occurred, resulting in the upregulation of active caspase 8 and its nuclear translocation. In conclusion we report that IND can induce time-dependent apoptotic and autophagic cell death of PCs. Our study provides the first indication of the interactions between these two homeostatic pathways in this context.

Friction-Induced Mitochondrial Dysregulation Contributes to Joint Deterioration in Prg4 Knockout Mice

Deficiency of PRG4 (lubricin), the boundary lubricant in mammalian joints, contributes to increased joint friction accompanied by superficial and upper intermediate zone chondrocyte caspase-3 activation, as shown in lubricin-null (Prg4^-/-) mice. Caspase-3 activity appears to be reversible upon the restitution of Prg4 either endogenously in vivo, in a gene trap mouse, or as an applied lubricant in vitro. In this study we show that intra-articular injection of human PRG4 in vivo in Prg4^-/- mice prevented caspase-3 activation in superficial zone chondrocytes and was associated with a modest decrease in whole joint friction measured ex vivo using a joint pendulum method. Non-lubricated Prg4^-/- mouse cartilage shows caspase cascade activation caused by mitochondrial dysregulation, and significantly higher levels of peroxynitrite (ONOO^- and ^-OH) and superoxide (O^-₂) compared to Prg4^+/+ and Prg4^+/- cartilage. Enzymatic activity levels of caspase 8 across Prg4 mutant mice were not significantly different, indicating no extrinsic apoptosis pathway activation. Western blots showed caspase-3 and 9 activation in Prg4^-/- tissue extracts, and the appearance of nitrosylated Cys163 in the active cleft of caspase-3 which inhibits its enzymatic activity. These findings are relevant to patients at risk for arthrosis, from camptodactyl-arthropathy-coxa vara-pericarditis (CACP) syndrome and transient lubricin insufficiency due to trauma and inflammation.

Linking deregulation of non-coding RNA to the core pathophysiology of Alzheimer's disease: An integrative review

The human genome encodes a vast repertoire of protein non-coding RNAs (ncRNA), some specific to the brain. MicroRNAs, which interfere with the translation of target mRNAs, are of particular interest since their deregulation has been implicated in neurodegenerative disorders like Alzheimer's disease (AD). However, it remains challenging to link the complex body of observations on miRNAs and AD into a coherent framework. Using extensive graphical support, this article discusses how a diverse panoply of miRNAs convergently and divergently impact (and are impacted by) core pathophysiological processes underlying AD: neuroinflammation and oxidative stress; aberrant generation of β-amyloid-42 (Aβ42); anomalies in the production, cleavage and post-translational marking of Tau; impaired clearance of Aβ42 and Tau; perturbation of axonal organisation; disruption of synaptic plasticity; endoplasmic reticulum stress and the unfolded protein response; mitochondrial dysfunction; aberrant induction of cell cycle re-entry; and apoptotic loss of neurons. Intriguingly, some classes of miRNA provoke these cellular anomalies, whereas others act in a counter-regulatory, protective mode. Moreover, changes in levels of certain species of miRNA are a consequence of the above-mentioned anomalies. In addition to miRNAs, circular RNAs, piRNAs, long non-coding RNAs and other types of ncRNA are being increasingly implicated in AD. Overall, a complex mesh of deregulated and multi-tasking ncRNAs reciprocally interacts with core pathophysiological mechanisms underlying AD. Alterations in ncRNAs can be detected in CSF and the circulation as well as the brain and are showing promise as biomarkers, with the ultimate goal clinical exploitation as targets for novel modes of symptomatic and course-altering therapy.

Comparison of Proteomics Profiles of Campylobacter jejuni Strain Bf under Microaerobic and Aerobic Conditions

Campylobacter jejuni accounts for one of the leading causes of foodborne bacterial enteritis in humans. Despite being considered an obligate microaerobic microorganism, C. jejuni is regularly exposed to oxidative stress. However, its adaptive strategies to survive the atmospheric oxygen level during transmission to humans remain unclear. Recently, the clinical C. jejuni strain Bf was singled out for its unexpected ability to grow under ambient atmosphere. Here, we aimed to understand better the biological mechanisms underlying its atypical aerotolerance trait using two-dimensional protein electrophoresis, gene expression, and enzymatic activities. Forty-seven proteins were identified with a significantly different abundance between cultivation under microaerobic and aerobic conditions. The over-expressed proteins in aerobiosis belonged mainly to the oxidative stress response, enzymes of the tricarboxylic acid cycle, iron uptake, and regulation, and amino acid uptake when compared to microaerobic conditions. The higher abundance of proteins related to oxidative stress was correlated to dramatically higher transcript levels of the corresponding encoding genes in aerobic conditions compared to microaerobic conditions. In addition, a higher catalase-equivalent activity in strain Bf was observed. Despite the restricted catabolic capacities of C. jejuni, this study reveals that strain Bf is equipped to withstand oxidative stress. This ability could contribute to emergence and persistence of particular strains of C. jejuni throughout food processing or macrophage attack during human infection.

Characterization and expression analysis of a caspase-2 in an invertebrate echinoderm sea cumber Apostichopus japonicus

Caspase-2 is the most evolutionarily conserved member of the caspase family which mediates the programmed cell death and plays crucial roles in key cellular processes. In this study, a caspase-2 homolog was identified and functionally characterized in sea cucumber Apostichopus japonicus, which we named AjCASP. The full-length cDNA consists of 2100 bp with an ORF encoding a protein of 378 amino acids. The deduced amino acid sequence shows that AjCASP consists of a conserved CARD-CASP2 domain and a CASs domain containing two active residues, two proteolytic cleavage residues, a substrate pocket and a dimer interface as well. In addition, a p20 large subunit with a characteristic five-peptide motif (QACRG) and a p10 small subunit in C-terminal were identified in CASs domain. Above data demonstrated that AjCASP is similar to CED-3 (the caspase-2 homolog of nematode Caenorhabditis elegans), which is further confirmed by phylogenetic tree analysis. AjCASP was ubiquitously expressed in sea cucumber and the obviously higher expression level was observed in coelomocyte, respiratory tree and intestine. Real-time PCR analyses further demonstrated that AjCASP was significantly induced by LPS. Taken together, these results strongly suggest that AjCASP is a caspase-2 homolog and it may be involved in invertebrate immune response, especially in eliminating and degrading invading pathogens.