Heat shock preconditioning modulates proliferation and apoptosis after superficial injury in isolated guinea pig gastric mucosa via an eicosanoid and protein synthesis-dependent mechanism

Experimental hyperlipidaemia does not prevent preconditioning and it reduces ischemia-induced apoptosis

BACKGROUND

Although ischemic preconditioning (PC) is known to confer cardioprotection in healthy subjects, it is unclear whether this phenomenon exists in the presence of hyperlipidaemia. The goal of this study was to determine whether the cardioprotective effect of PC is affected by hyperlipidaemia in a guinea pig model.

METHODS

We investigated the influence of preconditioning in normo- and hyperlipidaemic animals on papillary muscle contractility and myocardial damage as expressed by the percentage of apoptotic cells. Guinea pigs were fed a normal diet or a hyperlipidaemic diet for 5 weeks. Experiments were performed on papillary muscles subjected to experimental ischemia-reperfusion with or without prior PC.

RESULTS

The dietary treatment resulted in significant changes in lipid parameters, which had not affected the functionality of the right ventricle papillary muscle, both at basal conditions and in response to ischemia-reperfusion injury. However, it was found that the hyperlipidaemic diet had an effect on ischemia-induced apoptosis. Papillary muscles of hyperlipidaemic animals with higher HDL plasma concentrations were less susceptible to ischemia-reperfusion injury.

CONCLUSIONS

This study demonstrates that hyperlipidaemia does not alter the benefits of ischemic preconditioning such as a reduction of apoptosis and preservation of myocardial contractility. Additionally, it has been shown that plasma HDL may protect cardiomyocytes against ischemia-induced apoptosis.

Heat shock preconditioning induces protein carbonylation and alters antioxidant protection in superficially injured guinea pig gastric mucosa in vitro

According to our previous studies, heat shock preconditioning of gastric mucosa requires modulation of protein synthesis and eicosanoid pathways to induce protection against superficial injury. This may be caused by heat shock-induced oxidative stress. We studied the effect of heat shock preconditioning with normothermic recovery on redox status in superficially injured (1.25 mmol NaCl for 5 min) Ussing chamber perfused guinea pig gastric mucosa allowed to recover for 3 hr after injury. Protein oxidation, lipid peroxidation, level of superoxide dismutase, level of heat shock protein 72 (HSP72), and level of oxygen radical absorbance capacity were measured. Superficial injury increased lipid peroxidation. Heat shock preconditioning decreased oxygen radical absorbance capacity and increased protein carbonyl and HSP72 levels, but inhibited electrophysiologic recovery. Exposure to indomethacin and arachidonic acid (AA) partially abolished this pro-oxidative and inhibitory effect on recovery, but maintained HSP72 levels and decreased protein carbonyls, lipid peroxidation, and oxygen radical absorbance capacity. In conclusion, superficial injury increased lipid peroxidation. Heat shock preconditioning alone induced oxidative stress via indomethacin- and AA-sensitive mechanisms. The development of optimal cytoprotective strategy may therefore require control of oxidative stress and modulation of the eicosanoid pathways.

Heat Shock Preconditioning and Eicosanoid Pathways Modulate Caspase 3-Like Activity in Superficially Injured Isolated Guinea Pig Gastric Mucosa

BACKGROUND

After superficial mucosal injury, the disturbed gastric epithelial continuity is restored by cellular migration. Caspase-3 is an enzyme responsible for the execution of stress-induced apoptosis. Interestingly, heat shock proteins (Hsp) including Hsp60 are capable of modulating caspase-3 activity. Interestingly, we have demonstrated that heat shock preconditioning upregulates Hsp synthesis and inhibits restitution and cell proliferation via mechanisms related to de novo protein synthesis and eicosanoid pathways, both of which are crucial in the regulation of apoptosis and gastric mucosal defense systems.

AIMS

To assess whether caspase-3 activity is affected by heat shock preconditioning and associated pharmacological modulations after standard superficial injury to allow development of cytoprotective strategies.

METHODS

Guinea pig gastric mucosae were mounted and perfused in paired Ussing chambers. After heat shock (HS) preconditioning (42 degrees C) for 30 min, a superficial injury was induced (1.25 mol/l NaCl) followed by 3 h recovery. For mechanistic studies, the mucosa was exposed to 30 micromol/l arachidonic acid (AA) as a substrate for eicosanoid pathways, to 50 micromol/l quercetin (Q) to inhibit lipoxygenases, to 50 micromol/l indomethacin (In) to inhibit cyclo-oxygenases, or to 150 micromol/l cycloheximide (CHX) to inhibit de novo protein synthesis. After the experiment, the mucosa was prepared for analysis of caspase-3 activity. Hsp60 expression was analyzed to monitor the induction of heat shock response.

RESULTS

HS upregulated Hsp60 expression, indicating induction of the heat shock response without an effect on basal caspase-3 activity. Superficial injury itself did not affect caspase-3 activity nor Hsp60 synthesis. In all the experiments, exposure to CHX abolished caspase-3 activity and Hsp60 synthesis. AA+Q increased, Q decreased, while In+AA and In+AA+Q abolished caspase-3 activity independent of alterations in Hsp60 synthesis. Upon exposure to In+Q, HS decreased caspase-3 activity and upregulated Hsp60 synthesis.

CONCLUSION

Caspase-3 activity in isolated guinea pig gastric mucosa is regulated by mechanisms dependent on de novo protein synthesis and eicosanoid pathways but is not strictly related to Hsp synthesis. Upon modulation of the eicosanoid pathways, HS may be utilized to simultaneously decrease caspase-3 activity and increase Hsp synthesis. Modulations of the eicosanoid pathways may be utilized to reduce caspase-3 activity also upon normothermic conditions suggesting a novel mechanism by which caspase-3 is regulated in the gastric mucosa.