Heat shock proteins in cellular defense mechanisms and immunity

Disseminated neoplasia in cockles Cerastoderma edule: ultrastructural characterisation and effects on haemolymph cell parameters

Disseminated neoplasia (DN) has been detected in cockles from various beds in Galicia (NW Spain). A study was performed to characterise cockle neoplastic cell ultrastructure and to evaluate the effect of this disease at different severity stages on various haemolymph cell parameters. Examination of cockle neoplastic cells with transmission electron microscopy (TEM) showed round shapes and a lack of pseudopods, a high nucleus:cytoplasm diameter ratio, Golgi complexes, abundant mitochondria, ribosomes, and numerous endoplasmic reticulum tubes and electron-lucent vesicles. Various haemolymph cell parameters (cell mortality, non-specific esterase and lysosome biovolume, reactive oxygen intermediates [ROI] production, phagocytosis ability, intracellular Ca2+ and actin levels) were compared between DN severity categories by flow cytometry; haemocyte mortality, non-specific esterase activities and lysosome biovolume were found to be higher with increasing DN severity. The phagocytic ability of neoplastic cells was sharply reduced with regard to haemocytes. The cytoplasmic-free Ca2+ level was higher and actin content lower in haemolymph cells of diseased cockles compared to unaffected ones. A significant increase in ROI production was detected in later stages of disease progression.

Larval excretory-secretory products from the parasite Schistosoma mansoni modulate HSP70 protein expression in defence cells of its snail host, Biomphalaria glabrata

Synthesis of heat shock proteins (HSPs) following cellular stress is a response shared by many organisms. Amongst the HSP family, the approximately 70 kDa HSPs are the most evolutionarily conserved with intracellular chaperone and extracellular immunoregulatory functions. This study focused on the effects of larval excretory-secretory products (ESPs) from the parasite Schistosoma mansoni on HSP70 protein expression levels in haemocytes (defence cells) from its snail intermediate host Biomphalaria glabrata. S. mansoni larval stage ESPs are known to interfere with haemocyte physiology and behaviour. Haemocytes from two different B. glabrata strains, one which is susceptible to S. mansoni infection and one which is resistant, both showed reduced HSP70 protein levels following 1 h challenge with S. mansoni ESPs when compared to unchallenged controls; however, the reduction observed in the resistant strain was less marked. The decline in intracellular HSP70 protein persisted for at least 5 h in resistant snail haemocytes only. Furthermore, in schistosome-susceptible snails infected by S. mansoni for 35 days, haemocytes possessed approximately 70% less HSP70. The proteasome inhibitor, MG132, partially restored HSP70 protein levels in ESP-challenged haemocytes, demonstrating that the decrease in HSP70 was in part due to intracellular degradation. The extracellular signal-regulated kinase (ERK) signalling pathway appears to regulate HSP70 protein expression in these cells, as the mitogen-activated protein-ERK kinase 1/2 (MEK1/2) inhibitor, U0126, significantly reduced HSP70 protein levels. Disruption of intracellular HSP70 protein expression in B. glabrata haemocytes by S. mansoni ESPs may be a strategy employed by the parasite to manipulate the immune response of the intermediate snail host.

Heat-shock protein (HSP70) response in the eastern oyster, Crassostrea virginica, exposed to PAHs sorbed to suspended artificial clay particles and to suspended field contaminated sediments

Sediments are a potentially significant source of pollutants, containing not only organic contaminants but heavy metals as well. The heat shock protein response (HSP70 family) in the eastern oyster exposed to suspended clay particles spiked with polynuclear aromatic hydrocarbons (PAHs) and to suspended field contaminated sediments (SFCS) was investigated. In experiment 1, oysters were exposed to 1.0, 1.5 or 2.0 g suspended clay particles with concentrations of 65.6, 159.0 and 242 micro g PAHs per g of wet clay particles, respectively, and sampled after 40 days. Controls were exposed to 0, 1.0, 1.5, and 2.0 g suspended unspiked clay particles. In experiment 2, oysters were exposed to 0, 1.0, 1.5, and 2.0 g SFCS and the HSP70 expression was determined after 5, 10, 20 and 40 days exposure. Oysters exposed to suspended clay particles spiked with PAHs showed a significant increase in HSP70 levels, while oysters exposed to 1.0, 1.5 or 2.0 g suspended unspiked clay particles did not show changes (P=0.78) in HSP70 levels compared to the group receiving 0 g clay particles. Exposure to the SFCS resulted in a significant increase in HSP70 as a function of exposure (P<0.001) and treatment (P=0.006). The response, however, was not dose dependent. Compared to the control group (0 g SFCS), groups exposed to 1.0, 1.5 and 2.0 g SFCS reached significantly higher levels in HSP70 at 40 days of exposure, with those exposed to 2.0 g SFCS expressing the highest levels. The HSP70 expression for each treatment showed fluctuations at various time intervals. No mortalities were recorded during the exposure experiments. The major contaminants in the SFCS were PAHs, heavy metals and polychlorinated biphenyls (PCBs). These results reveal that exposure to PAHs sorbed to clay particles and to SFCS induced a HSP70 response in the eastern oyster.

Cloning and sequence analysis of a cDNA for an inducible 70 kDa heat shock protein (Hsp70) of the American oyster (Crassostrea virginica)

We have been investigating 70 kDa heat shock proteins (Hsp70s) as potential molecular markers for improved breeding and stress management to revitalize stocks of the American oyster, C. virginica. From a C. virginica visceral mass library, a 2.2 kb full-length cDNA was isolated that included a 634 amino acid open reading frame possessing approximately 80% sequence identity with inducible and constitutive Hsp70s of a broad array of animal species. Northern blotting indicated that the cloned cDNA preferentially recognized an mRNA of about 2 kb that was virtually absent from visceral mass under basal conditions but greatly increased after in vivo heat shock of American and Pacific oysters, suggesting that the cDNA codes for an inducible Hsp70.

The Yap1p-dependent induction of glutathione synthesis in heat shock response of Saccharomyces cerevisiae

Glutathione is synthesized in two sequential reactions catalyzed by gamma-glutamylcysteine synthetase (GSH1 gene product) and glutathione synthetase (GSH2 gene product). The expression of GSH1 in Saccharomyces cerevisiae has been known to be up-regulated by Yap1p, a critical transcription factor for the oxidative stress response in yeast. The present study demonstrates that GSH2 expression is also regulated by Yap1p under oxidative stress-induced conditions. In addition to oxidative stress, expression of GSH1 and GSH2 was induced by heat shock stress in a Yap1p-dependent manner with subsequent increases in intracellular glutathione content. Oxygen respiration rate increased when cells were exposed to higher temperatures, and as a result, intracellular oxidation levels were increased. The heat shock-induced expression of GSH1 and GSH2 did not occur under anaerobic conditions. Furthermore, even under aerobic conditions, the heat shock response of these genes was not observed when cells were pretreated with KCN to block oxygen respiration. We speculate that heat shock stress enhances oxygen respiration, which in turn results in an increase in the generation of reactive oxygen species in mitochondria. This signal may be mediated by Yap1p, resulting in the elevation of intracellular glutathione levels.

HSP70 expression in granulocytes and lymphocytes of patients with polytrauma: comparison with plasma glutamine

Heat shock proteins (HSP's) are a set of conserved proteins which confer tolerance to stress. These proteins play a major role in the pathophysiology of infection and inflammation. Induction of HSP's before onset of sepsis is able to reduce or prevent organ damage and death. GLN is known to influence the expression of HSP70 in different cell types. In this work we tried to find out if there is an association between plasma GLN levels and HSP70 expression in immune cells. We investigated six polytraumatized patients and a control group of six healthy donors. HSP70 expression was investigated by western blot analysis and immune-histochemistry. We demonstrated that granulocytes and lymphocytes behave differently in the expression of HSP70 in polytraumatized patients. In healthy donors both lymphocytes and granulocytes showed a pronounced expression of HSP70. In contrast, most of the polytraumatized patients showed no HSP70 expression in granulocytes. In lymphocytes of these patients, however, a pronounced expression similar to that of healthy volunteers was observed. Plasma glutamine levels were reduced in all patients and at normal range in healthy donors. These results suggest that lymphocytes and granulocytes behave different when confronted with a reduction of plasma GLN levels.

Cellular immunity: the final paradigm?

Cytotoxic T lymphocyte activation and most probably tolerance induction, is dependent on antigen presentation by a specialized group of cells, APC, including macrophages, dendritic cells and B cells. Since T lymphocytes are, at least, the majority of the time MHC molecule class-specific, CD8+ T cells require antigen presented by MHC class I molecules. MHC class I molecules are, however, restricted to presenting endogenously produced antigenic peptides. Most threats to the organism are of exogenous origin and do not uniformly affect all or even most of the cells of an organism. This precludes the likelihood that any number of APC would be involved in every threatening situation, which raises the important question of how T lymphocytes are indeed activated, especially CD8+ T cells (MHC class I restricted).

Bacterial endosymbiosis in amoebae

The large, free-living amoebae are inherently phagocytic. They capture, ingest and digest microbes within their phagolysosomes, including those that survive in other cells. One exception is an unidentified strain of Gram-negative, rod-shaped bacteria that spontaneously infected the D strain of Amoeba proteus and came to survive inside them. These bacteria established a stable symbiotic relationship with amoebae that has resulted in phenotypic modulation of the host and mutual dependence for survival.

Intestinal expression and cellular immune responses to human heat-shock protein 60 in Crohn's disease

Changes in the intestinal expression of the endogenous human 60-kDa heat-shock protein (HSP60) were investigated in patients with Crohn's disease. HSP60 immunoreactivity was detected in epithelial cells, vascular smooth muscle, and nerve cell bodies of both small and large bowel from patients with Crohn's disease. However, control tissue showed a similar pattern of HSP60 expression. Western blot analysis confirmed that the HSP60 immunoreactivity detected in the intestine corresponded to the 60-kDa HSP. The proliferative response of peripheral blood lymphocytes (PBL) and intestinal intraepithelial lymphocytes (IEL) to recombinant human HSP60 was examined. The results indicate that there was no significant difference in responses between patients with Crohn's disease and controls. Furthermore, there was no increase in the proportion of gamma/delta T cell receptor-bearing T cells in PBL from patients with Crohn's disease cultured for six days in the presence of human HSP60 as compared to control patients. These results suggest that endogenous human HSP60 is unlikely to be a target for an autoimmune response in patients with Crohn's disease.