Hsp40, a possible indicator for thermotolerance of murine tumour in vivo

Mesothelioma cells escape heat stress by upregulating Hsp40/Hsp70 expression via mitogen-activated protein kinases

Therapy with hyperthermal chemotherapy in pleural diffuse malignant mesothelioma had limited benefits for patients. Here we investigated the effect of heat stress on heat shock proteins (HSP), which rescue tumour cells from apoptosis. In human mesothelioma and mesothelial cells heat stress (39-42 degrees C) induced the phosphorylation of two mitogen activated kinases (MAPK) Erk1/2 and p38, and increased Hsp40, and Hsp70 expression. Mesothelioma cells expressed more Hsp40 and were less sensitive to heat stress compared to mesothelial cells. Inhibition of Erk1/2 MAPK by PD98059 or by Erk1 siRNA down-regulated heat stress-induced Hsp40 and Hsp70 expression and reduced mesothelioma cell survival. Inhibition of p38MAPK by SB203580 or siRNA reduced Hsp40, but not Hsp70, expression and also increased mesothelioma cell death. Thus hyperthermia combined with suppression of p38 MAPK or Hsp40 may represent a novel approach to improve mesothelioma therapy.

Effect of Withaferin A on the development and decay of thermotolerance in B16F1 melanoma: a preliminary study

Protein synthesis inhibitors can suppress the development of thermotolerance in tumor tissues during [corrected] repeated heating. Withaferin A (WA), isolated from Withania somnifera has cytotoxic and inhibitory action on protein synthesis. In the present investigation, effect of WA on development and decay of thermotolerance in B16F1 melanoma was studied in C57BL mice. Tumors of 100 +/- 10 [corrected] mm(3) size were subjected to repeated hyperthermia (HT) at 43 degrees C for 30 minutes. WA was injected after first hyperthermia treatment. The tumor response was assessed by calculating the tumor growth delay (GD). The GD increased with increase in time gap between two hyperthermia treatments and was significantly higher (p < 0.05 to p < 0.001) in WA treated groups at all the respective time gaps (except at 0h and 120h) compared to hyperthermia alone group. WA increases the tumor response during repeated hyperthermia by reducing the magnitude of thermotolerance developed and by decreasing the recovery time from thermotolerance.

Identification of genes responsive to low intensity pulsed ultrasound in a human leukemia cell line Molt-4

We examined the gene expression of human leukemia Molt-4 cells treated with non-thermal low intensity pulsed ultrasound. Six hours after 0.3W/cm(2) pulsed ultrasound treatment, apoptosis (24+/-3.3%, mean+/-SD) with minimal cell lysis was observed. Of approximately 16,600 genes analyzed, BCL2-associated athanogene 3 (BAG3), DnaJ (Hsp40) homolog, subfamily B, member 1 (DNAJB1), heat shock 70 kDa protein 1B (HSPA1B), and heat shock 70 kDa protein 6 (HSPA6) showed increased levels of expression while isopentenyl-diphosphate delta isomerase (IDI1) and 3-hydroxy-3-methylglutaryl-coenzyme A synthase 1 (HMGCS1) showed decreased levels in the cells 3h after the ultrasound treatment. The expression levels of these six genes were confirmed by a real-time quantitative polymerase chain reaction. To our knowledge, this is the first report of DNA microarray analysis of genes that are differentially expressed in response to apoptosis induced by non-thermal low intensity pulsed ultrasound in human leukemia cells. The present results will provide a basis for further understanding of the molecular mechanisms of effects of not only low intensity pulsed ultrasound but also that of mechanical shear stress in the cells.

cDNA array reveals mechanosensitive genes in chondrocytic cells under hydrostatic pressure

Hydrostatic pressure (HP) has a profound effect on cartilage metabolism in normal and pathological conditions, especially in weight-bearing areas of the skeletal system. As an important component of overall load, HP has been shown to affect the synthetic capacity and well-being of chondrocytes, depending on the mode, duration and magnitude of pressure. In this study we examined the effect of continuous HP on the gene expression profile of a chondrocytic cell line (HCS-2/8) using a cDNA array containing 588 well-characterized human genes under tight transcriptional control. A total of 51 affected genes were identified, many of them not previously associated with mechanical stimuli. Among the significantly up-regulated genes were immediate-early genes, and genes involved in heat-shock response (hsp70, hsp40, hsp27), and in growth arrest (GADD45, GADD153, p21(Cip1/Waf1), tob). Markedly down-regulated genes included members of the Id family genes (dominant negative regulators of basic helix-loop-helix transcription factors), and cytoplasmic dynein light chain and apoptosis-related gene NIP3. These alterations in the expression profile induce a transient heat-shock gene response and activation of genes involved in growth arrest and cellular adaptation and/or differentiation.

Geldanamycin induces heat shock proteins in brain and protects against focal cerebral ischemia

Geldanamycin (GA), a benzoquinone ansamycin, binds Hsp90 in vitro, releases heat shock factor (HSF1) and induces heat shock proteins (Hsps). Because viral and transgenic overexpression of Hsps protects cells against ischemia in vitro, we hypothesized that GA would protect brain from focal ischemia by inducing Hsps in vivo. Adult male Sprague-Dawley rats were subjected to 2-hour middle cerebral artery occlusions (MCAO) using the suture technique followed by 22-h reperfusions. GA or vehicle was injected into the lateral cerebral ventricles (i.c.v) 24 h before ischemia. Geldanamycin at 1 microg/kg decreased infarct volumes by 55.7% (p < 0.01) and TUNEL-positive cells by 30% in cerebral cortex. GA also improved behavioral outcomes (p < 0.01) and reduced brain edema (p < 0.05). Western blots showed that the 1 microg/kg GA dose induced Hsp70 and Hsp25 protein 8.2-fold and 2.7-fold, respectively, by 48 h following administration. Immunocytochemistry showed that GA induced Hsp70 in neurons and Hsp25 in glia and arteries in cortex, hippocampus, hypothalamus, and other brain regions. GA reduced co-immunoprecipitation of HSF1 with Hsp90 in brain tissue homogenates, promoted HSE-binding of HSF in brain nuclear extracts using gel shift assays, and increased luciferase reporter gene transcription for the Hsp70 promoter in PC12 cells. The data show that geldanamycin protects brain from focal ischemia and that this may be due, at least in part, to geldanamycin stimulation of heat shock gene transcription.

Expression of inducible Hsp70 enhances the proliferation of MCF-7 breast cancer cells and protects against the cytotoxic effects of hyperthermia

Heat shock proteins (Hsps) are ubiquitous proteins that are induced following exposure to sublethal heat shock, are highly conserved during evolution, and protect cells from damage through their function as molecular chaperones. Some cancers demonstrate elevated levels of Hsp70, and their expression has been associated with cell proliferation, disease prognosis, and resistance to chemotherapy. In this study, we developed a tetracycline-regulated gene expression system to determine the specific effects of inducible Hsp70 on cell growth and protection against hyperthermia in MCF-7 breast cancer cells. MCF-7 cells expressing high levels of Hsp70 demonstrated a significantly faster doubling time (39 hours) compared with nonoverexpressing control cells (54 hours). The effect of elevated Hsp70 on cell proliferation was characterized further by 5-bromo-2'deoxyuridine labeling, which demonstrated a higher number of second and third division metaphases in cells at 42 and 69 hours, respectively. Estimates based on cell cycle analysis and mean doubling time indicated that Hsp70 may be exerting its growth-stimulating effect on MCF-7 cells primarily by shortening of the G0/G1 and S phases of the cell cycle. In addition to the effects on cell growth, we found that elevated levels of Hsp70 were sufficient to confer a significant level of protection against heat in MCF-7 cells. The results of this study support existing evidence linking Hsp70 expression with cell growth and cytoprotection in human cancer cells.

Roles of molecular chaperones in the nervous system

Heat shock proteins (HSPs) are induced not only by heat shock but also by various other environmental stresses. HSPs such as Hsp90, Hsp70, Hsp60, Hsp40 and Hsp28 are also expressed constitutively at normal growth temperatures and have basic and indispensable functions in the life cycle of proteins as molecular chaperones, as well as playing a role in protecting cells from deleterious stresses. Recently, Hsc70 and Hsp40 were found to be localized to the synapse in the mammalian central nervous system, indicating a synaptic role for these HSPs. Molecular chaperones are able to inhibit the aggregation of partially denatured proteins and refold them. In addition, molecular chaperones, especially Hsp70, protect the brain and heart from severe ischemia. In these respects, there are expectations for the use of molecular chaperones for protection against and therapeutic treatment of inherited diseases caused by protein misfolding. In this study, we review Hsp70 and Hsp40, and refer to the roles of these molecules in the synapse and cytoprotective functions of HSPs in stress tolerance and neurodegenerative diseases.