Heat shock protein 90: a pathophysiological factor and novel treatment target in autoimmune bullous skin diseases.

The chaperone heat shock protein 90 (Hsp90), a cell stress-inducible molecule that regulates activity of many client proteins responsible for cellular growth, differentiation and apoptosis, has been proposed as an important therapeutic target in patients with malignancies. More recently, its active participation in (auto)immune processes has been recognized as evidenced by amelioration of inflammatory disease pathways through pharmacological inhibition of Hsp90 in rodent models of autoimmune encephalomyelitis, rheumatoid arthritis and systemic lupus erythematosus. Based on own current research results, this viewpoint essay provides important insights that Hsp90 is also involved as a notable pathophysiological factor in autoimmune blistering dermatoses including epidermolysis bullosa acquisita, bullous pemphigoid and possibly dermatitis herpetiformis. The observed in vitro, ex vivo and in vivo efficacy of anti-Hsp90 treatment in experimental models of autoimmune bullous diseases and its underlying multimodal anti-inflammatory mechanisms of interference with key contributors to autoimmune-mediated blister formation supports the introduction of selective non-toxic Hsp90 inhibitors into the clinical setting for the treatment of patients with these disorders.

Increased resistance of immobilized-stressed mice to infection: correlation with behavioral alterations.

Immobilization is an easy and convenient method to induce both psychological and physical stress resulting in restricted motility and aggression and is believed to be the most severe type of stress in rodent models. Although it has been generally accepted that chronic stress often results in immunosuppression while acute stress has been shown to enhance immune responses, the effects of IS on the host resistance to Escherichia coli (E. coli) infection and associated behavioral changes are still not clear. In a series of experiments aimed at determining the level of hypothalamic COX-2, HSP-90, HSP-70, SOD-1 and plasma level of corticosterone, cytokine, antibody titer and their association with behavioral activities, mice were infected with viable E. coli during acute and chronic IS by taping their paws. In this study we show that acute and chronic IS enhances the resistance of mice to E. coli infection via inhibiting the production of pro-inflammatory cytokines, free radicals, and by improving the exploratory behavior. Altogether, our findings support the notion that cytokines released during immune activation and under the influence of corticosterone can modulate the open field behavior both in terms of locomotor activity as well as exploration. One of the features observed with chronic stressor was a lower ability to resist bacterial infection, although in case of acute stress, a better clearance of bacterial infection was observed in vivo with improvement of exploratory behavior and cognitive functions.

Hyperthermia-induced DNA repair deficiency suggests novel therapeutic anti-cancer strategies.

Local hyperthermia is an effective treatment modality to augment radio- and chemotherapy-based anti-cancer treatments. Although the effect of hyperthermia is pleotropic, recent experiments revealed that homologous recombination, a pathway of DNA repair, is directly inhibited by hyperthermia. The hyperthermia-induced DNA repair deficiency is enhanced by inhibitors of the cellular heat-shock response. Taken together, these results provide the rationale for the development of novel anti-cancer therapies that combine hyperthermia-induced homologous recombination deficiency with the systemic administration of drugs that specifically affect the viability of homologous recombination deficient cells and/or inhibit the heat-shock response, to locally sensitise cancer cells to DNA damaging agents.

Black tea polyphenols induce human leukemic cell cycle arrest by inhibiting Akt signaling: possible involvement of Hsp90, Wnt/ß-catenin signaling and FOXO1.

Tea polyphenols have potent biological activities against human cancer cells. A major causative factor in malignancies is disregulation of cell-cycle kinetics. In this study, we observed that black tea polyphenols, theaflavins (TF) and thearubigins (TR) induced cell-cycle arrest at the G(0) /G(1) phase in human leukemic U937 and K562 cells. Our objective was to understand the underlying molecular mechanism of cell-cycle inhibition by TF and TR. During elucidation, we observed that both TF and TR treatment augmented expression of p19, p21 and p27, while ablating cylcin-dependent kinase (CDK)2, CDK4, CDK6 and cyclin D1 levels. Our experimental results further determined that Akt signaling suppression by TF and TR played a major role in this process. Moreover, suppression of glycogen synthase kinase-3ß, ß-catenin and amplification of forkhead transcription factor 1 (FOXO1) expression were associated with regulation of certain key components of the cell-cycle machinery. In addition, depletion of heat shock protein (Hsp) 90 by TF and TR also had a pivotal role in cell-cycle arrest. More specifically, inhibition of Akt signaling by TF and TR correlated with the depletion of its downstream targets like Wnt/ß-catenin signaling, cyclin D1 and increase of FOXO1, p27 levels. Inhibition of upstream Hsp90 by TF and TR consequently attenuated Akt signaling and reduced the level of CDK2. These results suggest possible mechanisms for the chemopreventive effect of TF and TR on human leukemic cells. To our knowledge, this is the first report of such a detailed molecular mechanism for TF and the less-investigated polyphenol TR-mediated cell-cycle inhibition in human leukemic U937 and K562 cells.

Heat shock protein 90 mediates cytoprotection by H2S against chemical hypoxia-induced injury in PC12 cells.

1. Increasing evidence indicates that hydrogen sulphide (H2S) may serve as an important biological cytoprotective agent. Heat shock protein (Hsp) 90 can attenuate stress-induced injury. However, whether Hsp90 mediates the cytoprotective effect of H2S against chemical hypoxia-induced injury in PC12 cells is not known. 2. In the present study, CoCl2 (a chemical hypoxia mimetic) was used to treat PC12 cells to create a model of chemical hypoxia. To explore the role of Hsp90 in the cytoprotection afforded by H2S against chemical hypoxia-induced injury, 2 µmol/L 17-allylaminogeldanamycin (17-AAG), a selective inhibitor of Hsp90, was administered for 30 min prior to preconditioning with 400 µmol/L NaHS, followed by chemical hypoxia. 3. Cobalt chloride reduced cell viability (by 52.7 ± 1.5%), increased PC12 cell apoptosis (by 42.1 ± 1.5%), induced reactive oxygen species (ROS) by 3.79% compared with control and induced the dissipation of mitochondrial membrane potential (MMP) by 2.56% compared with control. 4. Pretreatment of PC12 cells with 100-400 µmol/L sodium hydrosulphide (NaHS), an H2S donor, for 3 h prior to exposure to 600 µmol/L CoCl2 provided significant, concentration-dependant protection to PC12 cells against CoCl2-induced cytotoxicity. Specifically, pretreatment of PC12 cells with 400 µmol/L NaHS decreased apoptosis to 16.77 ± 1.77% and blocked the CoCl2-induced increase in ROS production and loss of MMP. 5. At 400 µmol/L, NaHS upregulated Hsp90 in a time-dependant manner (over the period 0-180 min). In addition to its effects on Hsp90 expression, NaHS pretreatment of PC12 cells augmented the overexpression of Hsp90 induced by 600 µmol/L CoCl2 by 1.38-fold (P < 0.01). 6. Treatment of PC12 cells with 2 µmol/L 17-AAG for 30 min prior to NaHS pretreatment blocked the overexpression of Hsp90 induced by NaHS preconditioning, as evidenced by decreased cell viability (by 54.2 + 1.2%; P < 0.01), increased PC12 cell apoptosis (by 36.6 ± 1.2%; P < 0.01) and increasing ROS production. 7. The findings of the present study provide novel evidence that Hsp90 mediates H2S-induced neuroprotection against chemical hypoxia-induced injury via anti-oxidant and anti-apoptotic effects.

Harnessing Hsp90 function as a powerful, broadly effective therapeutic strategy for fungal infectious disease.

Invasive fungal infections are a leading cause of mortality among immunocompromised individuals. Treatment is notoriously difficult with the limited armamentarium of antifungal drugs, whose efficacy is compromised by host toxicity, a limited activity spectrum, or the emergence of drug resistance. We previously established that the molecular chaperone Hsp90 enables the emergence and maintenance of fungal drug resistance. For the most prevalent fungal pathogen of humans, Candida albicans, Hsp90 mediates resistance to azoles, which inhibit ergosterol biosynthesis and are the most widely deployed antifungals in the clinic. For the emerging opportunistic pathogen Aspergillus terreus, Hsp90 is required for basal resistance to echinocandins, which inhibit beta(1, 3)-glucan synthesis and are the only new class of antifungals to reach the clinic in decades. Here, we explore the therapeutic potential of Hsp90 inhibitors in fungal disease using a tractable host-model system, larvae of the greater wax moth Galleria mellonella, and a murine model of disseminated disease. Combination therapy with Hsp90 inhibitors that are well tolerated in humans and an azole rescued larvae from lethal C. albicans infections. Combination therapy with an Hsp90 inhibitor and an echinocandin rescued larvae from infections with the most lethal mold, Aspergillus fumigatus. In a murine model of disseminated candidiasis, genetic compromise of C. albicans HSP90 expression enhanced the therapeutic efficacy of an azole. Thus, harnessing Hsp90 provides a much-needed strategy for improving the treatment of fungal disease because it enhances the efficacy of existing antifungals, blocks the emergence of drug resistance, and exerts broad-spectrum activity against diverse fungal pathogens.

Involvement of tumor necrosis factor receptor-associated protein 1 (TRAP1) in apoptosis induced by beta-hydroxyisovalerylshikonin.

beta-Hydroxyisovalerylshikonin (beta-HIVS), a compound isolated from the traditional oriental medicinal herb Lithospermum radix, is an ATP non-competitive inhibitor of protein-tyrosine kinases, such as v-Src and EGFR, and it induces apoptosis in various lines of human tumor cells. However, the way in which beta-HIVS induces apoptosis remains to be clarified. In this study, we performed cDNA array analysis and found that beta-HIVS suppressed the expression of the gene for tumor necrosis factor receptor-associated protein 1 (TRAP1), which is a member of the heat-shock family of proteins. When human leukemia HL60 cells and human lung cancer DMS114 cells were treated with beta-HIVS, the amount of TRAP1 in mitochondria decreased in a time-dependent manner during apoptosis. A similar reduction in the level of TRAP1 was also observed upon exposure of cells to VP16. Treatment of DMS114 cells with TRAP1-specific siRNA sensitized the cells to beta-HIVS-induced apoptosis. Moreover, the reduction in the level of expression of TRAP1 by TRAP1-specific siRNA enhanced the release of cytochrome c from mitochondria when DMS114 cells were treated with either beta-HIVS or VP16. The suppression of the level of TRAP1 by either beta-HIVS or VP16 was blocked by N-acetyl-cysteine, indicating the involvement of reactive oxygen species (ROS) in the regulation of the expression of TRAP1. These results suggest that suppression of the expression of TRAP1 in mitochondria might play an important role in the induction of apoptosis caused via formation of ROS.