Heat shock proteins as cellular lifeguards

Resistance to apoptosis is a mechanism of adaptation of rat stomach to aspirin

Adaptation of the gastric mucosa to nonsteroidal anti-inflammatory drug-induced injury is a well-documented phenomenon, but the mechanisms are not known. We investigated whether changes in stress protein expression and apoptosis play roles in adaptation of rat stomach to aspirin. RT-PCR and Western blotting techniques were used to analyze mRNA and protein expression of HSP72 and HSP90 and cleavage of caspase 3 protein. Apoptosis was detected by the TUNEL method and quantified. HSP72 mRNA and protein expression was unchanged in adapted mucosa, whereas HSP90 mRNA and protein levels decreased. Caspase 3 protein was activated, and the number of apoptotic cells increased in mucosa after one aspirin dose. However, in adapted mucosa after aspirin, activated caspase 3 and the number of apoptotic cells had returned to basal levels. Induction of the stress response was found not to be a mechanism of mucosal adaptation against multiple doses of aspirin. Our results lead us to propose instead that resistance to aspirin-induced apoptosis plays a role in the protective phenomenon of adaptation.

Pro-apoptotic treatment with an adenovirus encoding Bax enhances the effect of chemotherapy in ovarian cancer

BACKGROUND

Tumor cell heterogeneity and resistance to chemotherapy-mediated cell death are major obstacles in cancer therapy. It has been reported that expression of the pro-apoptotic molecule Bax can induce cell death or sensitize tumor cells to chemotherapy in stable cell clones derived from tumor cells. However, these studies are limited in that they cannot represent the heterogeneity of cancer cells observed in vivo. In this study, we have further explored the therapeutic potential of Bax.

METHODS

Using an inducible recombinant Bax adenovirus, we screened a panel of ovarian cancer cell lines and primary patient-derived ovarian tumor cells for their sensitivity to Bax-mediated cytotoxicity. Apoptotic cell death was evaluated qualitatively with Hoechst staining and quantitatively with MTS and Annexin V-based assays. Endogenous levels of both Bcl-2 and Bax protein and p53 status were evaluated. The potential of bax to sensitize ovarian cancer lines to chemotherapy was also tested. Dose-response curves were generated to evaluate cell death.

RESULTS

Overexpression of Bax directly induced apoptosis in both ovarian cancer cell lines and the patient-derived primary cancer cells. However, the sensitivity of these cells to Bax varied and appeared to be independent of both the status of p53 and the endogenous levels of bcl-2 or Bax, critical molecules in the apoptotic pathway. Importantly, overexpression of Bax significantly enhanced chemotherapy-induced cytotoxicity in both established cell lines and primary ovarian carcinoma cells.

CONCLUSIONS

These studies suggest that overexpression of Bax alone or in combination with chemotherapy may provide a means to overcome the problems imposed by the heterogeneous nature of tumors, ultimately augmenting the efficacy of chemotherapy in patients suffering from ovarian cancer.

Microcirculatory dysfunction in sepsis: a pathogenetic basis for therapy?

Sepsis is a frequent complication of multiple organ dysfunction syndrome and remains a major problem of intensive care medicine. It is also a common factor in the final cause of death in hospital populations. Clinical observations, assisted by invasive monitoring techniques as well as pathological-anatomical studies, clearly indicate that microcirculatory dysfunction lies at the centre of sepsis pathogenesis. Numerous animal models, from rodents to primates, many of which employ bacteria or their toxins, especially endotoxins, have helped to shed light on the pathomechanisms leading to this dysregulation in the peripheral circulation. Among these are activation of humoral and cellular inflammatory mediator systems, with special emphasis on neutrophil-endothelial interactions, affecting endothelial barrier function and vasoregulation and ultimately leading to severely perturbed oxygen transport and utilization. In vitro studies have provided more insight into the molecular mechanisms involved in this microcirculatory dysfunction, although much more attention must be directed towards microvascular endothelial cells and the role of heterogeneity of response in various vascular beds. These experimental data must in turn be validated by comparing with the human in situ situation, both clinical and morphological. This review aims at a critical appraisal of the clinical and experimental evidence for sepsis-induced dysregulation of the microcirculation and how knowledge of the underlying cellular and molecular pathology could be used to make therapy more rational and effective. To date, therapeutic approaches, such as anti-cytokine and anti-oxidant regimens, which have been highly successful in experimental models, have failed to demonstrate clinical efficacy. Newer approaches, such as targeting the coagulation system, nitric oxide synthesis or intracellular signal transduction, are also discussed. The necessity to focus on the role of anti-inflammatory mediators, as well as the pathogenetic significance of important molecular groups, such as the heat shock proteins, which until now have been given scant attention, will be stressed.