Heat shock protein 70 overexpression protects LLC-PK1 tubular cells from heat shock but not hypoxia

Gene expression profiling to identify the toxicities and potentially relevant human disease outcomes associated with environmental heavy metal exposure

Heavy metals are the most commonly encountered toxic substances that increase susceptibility to various diseases after prolonged exposure. We have previously shown that healthy volunteers living near a mining area had significant contamination with heavy metals associated with significant changes in the expression of some detoxifying genes, xenobiotic metabolizing enzymes, and DNA repair genes. However, alterations of most of the molecular target genes associated with diseases are still unknown. Thus, the aims of this study were to (a) evaluate the gene expression profile and (b) identify the toxicities and potentially relevant human disease outcomes associated with long-term human exposure to environmental heavy metals in mining area using microarray analysis. For this purpose, 40 healthy male volunteers who were residents of a heavy metal-polluted area (Mahd Al-Dhahab city, Saudi Arabia) and 20 healthy male volunteers who were residents of a non-heavy metal-polluted area were included in the study. Total RNA was isolated from whole blood using PAXgene Blood RNA tubes and then reversed transcribed and hybridized to the gene array using the Affymetrix U219 GeneChip. Microarray analysis showed about 2129 genes were identified and differentially altered, among which a shared set of 425 genes was differentially expressed in the heavy metal-exposed groups. Ingenuity pathway analysis revealed that the most altered gene-regulated diseases in heavy metal-exposed groups included hematological and developmental disorders and mostly renal and urological diseases. Quantitative real-time polymerase chain reaction closely matched the microarray data for some genes tested. Importantly, changes in gene-related diseases were attributed to alterations in the genes encoded for protein synthesis. Renal and urological diseases were the diseases that were most frequently associated with the heavy metal-exposed group. Therefore, there is a need for further studies to validate these genes, which could be used as early biomarkers to prevent renal injury.

Hsp72 is an early and sensitive biomarker to detect acute kidney injury

This study was designed to assess whether heat shock protein Hsp72 is an early and sensitive biomarker of acute kidney injury (AKI) as well as to monitor a renoprotective strategy. Seventy-two Wistar rats were divided into six groups: sham-operated and rats subjected to 10, 20, 30, 45 and 60 min of bilateral ischemia (I) and 24 h of reperfusion (R). Different times of reperfusion (3, 6, 9, 12, 18, 24, 48, 72, 96 and 120 h) were also evaluated in 30 other rats subjected to 30 min of ischemia. Hsp72 messenger RNA (mRNA) and protein levels were determined in both kidney and urine. Hsp72-specificity as a biomarker to assess the success of a renoprotective intervention was evaluated in rats treated with different doses of spironolactone before I/R. Renal Hsp72 mRNA and protein, as well as urinary Hsp72 levels, gradually increased relative to the extent of renal injury induced by different periods of ischemia quantified by histomorphometry as a benchmark of kidney damage. Urinary Hsp72 increased significantly after 3 h and continued rising until 18 h, followed by restoration after 120 h of reperfusion in accord with histopathological findings. Spironolactone renoprotection was associated with normalization of urinary Hsp72 levels. Accordingly, urinary Hsp72 was significantly increased in patients with clinical AKI before serum creatinine elevation. Our results show that urinary Hsp72 is a useful biomarker for early detection and stratification of AKI. In addition, urinary Hsp72 levels are sensitive enough to monitor therapeutic interventions and the degree of tubular recovery following an I/R insult.

Investigating the role of ischemia vs. elevated hydrostatic pressure associated with acute obstructive uropathy

Obstructive uropathy can cause irreversible renal damage. It has been hypothesized that elevated hydrostatic pressure within renal tubules and/or renal ischemia contributes to cellular injury following obstruction. However, these assaults are essentially impossible to isolate in vivo. Therefore, we developed a novel pressure system to evaluate the isolated and coordinated effects of elevated hydrostatic pressure and ischemic insults on renal cells in vitro. Cells were subjected to: (1) elevated hydrostatic pressure (80 cm H(2)O); (2) ischemic insults (hypoxia (0% O(2)), hypercapnia (20% CO(2)), and 0 mM glucose media); and (3) elevated pressure + ischemic insults. Cellular responses including cell density, lactate dehydrogenase (LDH) release, and intracellular LDH (LDH(i)), were recorded after 24 h of insult and following recovery. Data were analyzed to assess the primary effects of ischemic insults and elevated pressure. Unlike pressure, ischemic insults exerted a primary effect on nearly all response measurements. We also evaluated the data for insult interactions and identified significant interactions between ischemic insults and pressure. Altogether, findings indicate that pressure may sub-lethally effect cells and alter cellular metabolism (LDH(i)) and membrane properties. Results suggest that renal ischemia may be the primary, but not the sole, cause of cellular injury induced by obstructive uropathy.

Na+/K+ -ATPase stabilization by Hsp70 in the outer stripe of the outer medulla in rats during recovery from a low-protein diet

A low-protein (LP) diet induces injury from energy depletion in renal epithelial cells. Overexpression of heat-shock proteins has been implicated in the restoration of the cytoskeletal anchorage of Na(+)/K(+)-ATPase. We tested if Hsp70 stabilizes renal Na(+)/K(+)-ATPase attachment to the cytoskeleton from the cortex and the outer stripe of the outer medulla (OSOM) in rats during recovery from a LP diet. Rats were fed with a LP diet (8% protein) for 14 days, and then the rats were recovered with a 24% protein (RP) diet. The control group received a 24% protein (NP) diet. Increased Na(+)/K(+)-ATPase dissociation was demonstrated in soluble fraction from OSOM with lower ATP content as a result of LP diet vs NP. Meanwhile, decreased Hsp70 levels in the same fraction were shown. Translocation of Hsp70 to the cytoskeletal injured fraction associated with stabilization of Na(+)/K(+)-ATPase was shown in OSOM from LP after in vitro co-incubation of the cytoskeletal fraction of LP and non-cytoskeletal fraction of RP. These effects were abolished by the addition of the anti-Hsp70 antibody. Absence of Na(+)/K(+)-ATPase detachment from its cytoskeletal anchorage was demonstrated in proximal duct segments from cortex in LP. Co-immunoprecipitation showed that the amount of Na(+)/K(+)-ATPase co-precipitating with Hsp70 increased in the OSOM as a result of the LP diet. In the cortex tissues from rats fed the LP and the RP diet, the interaction of both proteins were similar to the control groups. Our results indicate that Hsp70 has a critical role in protecting the integrity of the cytoskeletal anchorage of Na(+)/K(+)-ATPase during recovery from ATP-depleted injury resulting from LP in OSOM.

Experimental strategies to improve in vitro models of renal ischemia

Ischemia has elicited a great deal of interest among the scientific community due to its role in life-threatening pathologies such as cancer, stroke, acute renal failure, and myocardial infarction. Oxygen deprivation (hypoxia) associated with ischemia has recently become a subject of intense scrutiny. New investigators may find it challenging to induce hypoxic injury in vitro. Researchers may not always be aware of the experimental barriers that contribute to this phenomenon. Furthermore, ischemia is associated with other major insults, such as excess carbon dioxide (hypercapnia), nutrient deprivation, and accumulation of cellular wastes. Ideally, these conditions should also be incorporated into in vitro models. Therefore, the motivation behind this review is to: i. delineate major in vivo ischemic insults; ii. identify and explain critical in vitro parameters that need to be considered when simulating ischemic pathologies; iii. provide recommendations to improve experiments; and as a result, iv. enhance the validity of in vitro results for understanding clinical ischemic pathologies. Undoubtedly, it is not possible to completely replicate the in vivo environment in an ex vivo model system. In fact, the primary goal of many in vitro studies is to elucidate the role of specific stimuli during in vivo pathological events. This review will present methodologies that may be implemented to improve the applicability of in vitro models for understanding the complex pathological mechanisms of ischemia. Finally, although these topics will be discussed within the context of renal ischemia, many are pertinent for cellular models of other organ systems and pathologies.

Increased expression of heat shock protein 72 protects renal proximal tubular cells from gentamicin-induced injury

The nephrotoxicity of gentamicin (GM) has been widely recognized. Heat shock protein 72 (HSP72) has been reported to be a cytoprotectant. However, its cytoprotective effect against GM induced kidney injury has not yet been studied. In this study, we investigated the cytoprotective effect of HSP72 on GM-induced nephrotoxicity in vitro. Human Kidney tubular cell line, HK-2 cells were divided into four groups: control group, GM group (cells incubated with GM only), heat shock (HS) group (cells incubated at 43 degrees C for 30 min), and GM plus HS group, respectively. Lactate dehydrogenase (LDH) release increased time-dependently from 24 hr to 96 hr compared to the data of cells treated with GM only. Results of NAG activities, superoxide dismutase (SOD) activities and malondialdehyde (MDA) content were similar to that of the LDH release. The amount of HSP72 positive cells increased significantly at 72 hr after cells were treated with GM only. Both HSP72 protein and gene expression increased significantly at 72 hr when cells were treated with GM. On the other hand, HS induced HSP72 expression markedly. Pretreatment of HS inhibited HK-2 cells from GM-induced injury. It could reduce LDH release and NAG activity. HS also increased SOD activity, and decreased MDA content when cells were damaged by GM. These findings suggested that HS may protect kidney cells from GM-induced injury. Pre-induction of HSP72 may provide therapeutic strategies for nephrotoxicity induced by GM.

Transcriptomic changes in developing kidney exposed to chronic hypoxia

cDNA arrays compared gene expression in kidneys of neonatal mice subjected to 1, 2, and 4 weeks of chronic constant (CCH) or intermittent (CIH) hypoxia with normoxic littermates. Five to twenty percent of genes were regulated in each condition, with greater changes in CCH. Up-regulation of 42% of the solute carriers after 1 week of CCH suggests a strong activation of pH controlling pathways. Significant reduction in expression change of genes important in growth, development, and aging as a function of time indicates reduced maturation rate in CIH and CCH treatments. Regulated genes showed gender dependence in CCH, being higher in females than males at 1 week and higher in males than females thereafter. Transcriptional control was enhanced in CCH but not in CIH. Thus, CCH and CIH both alter gene expression and retard maturation with the more profound changes occurring in CCH than in CIH.

Increased expression of heat shock protein (HSP)72 in a human proximal tubular cell line (HK-2) with gentamicin-induced injury

Gentamicin (GM) has been widely used as an antibiotic and its nephrotoxicity has been recognized. However, the alternation of heat shock protein (HSP) 72 as an inductive protein in proximal tubular cells treated with GM is still unclear. In this study, GM cytotoxicity and its effect on the expression of HSP72 in human kidney proximal tubular (HK-2) cells were measured. HK-2 cells were incubated for 24 hr, 48 hr, 72 hr, and 96 hr with GM only and GM plus MnCl2, respectively. Cytotoxicity was determined by the release of lactate dehydrogenase (LDH). Activity of N-acetyl-beta-D-glucosaminidase (NAG) and effects of GM on oxidation in HK-2 cells were investigated by measurements of malondialdehyde (MDA) content and superoxide dismutase (SOD) activity, and the ability of viable cells to reduce a tetrazolium-based compound (MTT). The expression of HSP72 was measured by immunocytochemistry, Western blotting and RT-PCR. Cells were exposed to GM at a concentration of 100 microg/ml. After 24 hr MTT uptake decreased significantly and then gradually until 96 hr. LDH release increased time-dependently from 24 hr to 72 hr, but decreased at 96 hr compared with the data at 72 hr when cells were treated with GM only. Both results of NAG and SOD activities and results of MDA content were similar to that of the LDH release. The amount of HSP72 positive cells increased at 24 hr after exposure to GM up to 72 hr. HSP72 expression increased significantly from 24 hr, and reached its peak at 72 hr when cells were treated with GM only. Furthermore, the change of the HSP72 gene transcription was similar to the expression of HSP72. These results demonstrated that GM treatment could induce damage to HK-2 cells and that the expression of HSP72 increased when cells were injured by GM.

Optimizing the factors which modify thermal enhancement of melphalan in a spontaneous murine tumor

BACKGROUND

Hyperthermia enhances the cytotoxicity of some chemotherapeutic agents. Both clinical and laboratory studies suggest melphalan may be an important drug when hyperthermia is added to chemotherapy treatments. Factors that may modify the thermal enhancement of melphalan were studied to optimize its clinical use with hyperthermia.

METHODS

The tumor studied was an early-generation isotransplant of a spontaneous C3Hf/Sed mouse fibrosarcoma, Fsa-II. All studies were performed under supervision of the Animal Care and Use Committee. Hyperthermia was administered by immersing the tumor-bearing foot into a constant temperature water bath. Four factors were studied: duration of hyperthermia, sequencing of hyperthermia and melphalan, intensity of hyperthermia, and tumor size. To study duration of hyperthermia tumors were treated at 41.5 degrees C for 30 or 90 min immediately after intraperitoneal administration of melphalan. For sequencing of hyperthermia and melphalan, animals received hyperthermia treatment of tumors for 30 min at 41.5 degrees C immediately after drug administration, both immediately and 3 h after administration of drug or only at 3 h after administration of drug. Intensity of hyperthermia was studied using heat treatment of tumors for 30 min at 41.5 or 43.5 degrees C immediately following drug administration. Effect of tumor size was studied by delaying experiments until three times the tumor volume (113 mm3) was observed. Treatment of tumors was for 30 min at 41.5 degrees C immediately following drug administration. Tumor response was studied by the mean tumor growth time.

RESULTS

Hyperthermia in the absence of melphalan had a small but significant effect on tumor growth time at 43.5 degrees C but not at 41.5 degrees C. Hyperthermia at 41.5 degrees C immediately after melphalan administration doubled mean tumor growth time at 30 min and caused a threefold increase at 90 min (P=0.0002) when compared to tumors treated with melphalan alone at room temperature. Application of hyperthermia for one-half hour immediately following drug administration was the most effective in delaying tumor growth. No significant difference in mean tumor growth time was observed with an increase in temperature from 41.5 to 43.5 degrees C. For large tumors heat alone and melphalan alone caused a moderate increase in tumor growth delay. These effects in large tumors were greatly increased by a combination of chemotherapy and hyperthermia.

CONCLUSIONS

From our data it would appear that the administration of intraperitoneal melphalan immediately prior to 90 min of heat at 41.5 degrees C may optimize anti-neoplastic activity. These data may be useful in formulating clinical protocols in which melphalan and heat are combined.

The role of heat shock proteins Hsp70 and Hsp27 in cellular protection of the central nervous system

Heat shock proteins (Hsps) are highly conserved and under physiological conditions act as molecular chaperones and/or have anti-apoptotic activities. Expression in the brain of two heat shock proteins, the70 kDa Hsp (Hsp70) and the 27 kDa Hsp (Hsp27), is notable because both proteins are highly inducible in glial cells and neurons following a wide range of noxious stimuli including ischemia, epileptic seizure and hyperthermia. In the central nervous system, constitutive expression of Hsp27 is limited to many (but not all) sensory and motor neurons of the brain stem and spinal cord, while there is little or no constitutive expression of Hsp70. However, inducible expression of both Hsp70 and Hsp27 is present in many areas of the brain and retina and is associated with cellular resistance to a variety of insults. The potential for manipulating the expression levels of Hsps for therapeutic advantage in neurodegenerative diseases such as Alzheimer's disease, stroke and glaucoma will be explored.

Loss of Hsp70 in Drosophila is pleiotropic, with effects on thermotolerance, recovery from heat shock and neurodegeneration

The heat-shock response is a programmed change in gene expression carried out by cells in response to environmental stress, such as heat. This response is universal and is characterized by the synthesis of a small group of conserved protein chaperones. In Drosophila melanogaster the Hsp70 chaperone dominates the profile of protein synthesis during the heat-shock response. We recently generated precise deletion alleles of the Hsp70 genes of D. melanogaster and have used those alleles to characterize the phenotypes of Hsp70-deficient flies. Flies with Hsp70 deletions have reduced thermotolerance. We find that Hsp70 is essential to survive a severe heat shock, but is not required to survive a milder heat shock, indicating that a significant degree of thermotolerance remains in the absence of Hsp70. However, flies without Hsp70 have a lengthened heat-shock response and an extended developmental delay after a non-lethal heat shock, indicating Hsp70 has an important role in recovery from stress, even at lower temperatures. Lack of Hsp70 also confers enhanced sensitivity to a temperature-sensitive lethal mutation and to the neurodegenerative effects produced by expression of a human polyglutamine disease protein.

Overexpression of HSP-72 confers cytoprotection in experimental peritoneal dialysis

BACKGROUND

Peritoneal dialysis is complicated by mesothelial cell injury due to low biocompatibility of peritoneal dialysis fluid (PDF). We have previously demonstrated that heat shock protein (HSP)-72 is potently up-regulated in response to PDF exposure of mesothelial cells in in vitro and in vivo models of peritoneal dialysis. The aim of this study was to evaluate potential cytoprotective effects of overexpression of HSP-72.

METHODS

Cytoprotection was assessed by comparing cellular viability between pretreated versus nonpretreated human mesothelial cells (Met 5a; ATCC, Manassas, VA, USA, and primary cell cultures) subjected to extended, usually lethal PDF exposure times (120 min, CAPD2; Fresenius, Bad Homburg, Germany). Pretreatment was performed with exposure to PDF (60 min, CAPD2; Fresenius) or heat (15 min, 41.5 degrees C), and by transient transfection with HSP-72.

RESULTS

When mesothelial cells were pretreated by nonlethal exposure to PDF or heat, HSP-72 was markedly up-regulated (>5-fold, P < 0.01). Pretreated human mesothelial cells were significantly protected against subsequent "lethal" exposures to PDF, as assessed by dye exclusion (>50% reduction, P < 0.05) and lactate dehydrogenase (LDH) release (>30% reduction, P < 0.05). Comparable cytoprotection (50% reduction by dye exclusion) was indicated by overexpression of HSP-72 in cultered human mesothelial cells (>5-fold) after transient transfection with HSP-72. This cytoprotection was confirmed at a cellular basis by double staining techniques with HSP-72 and ApopTag (apoptosis detection kit).

CONCLUSION

Our study therefore shows that the mesothelial stress response confers cytoprotection in experimental peritoneal dialysis, mediated by the induction of HSP-72, and that the stimulus of the pretreatment does not have to be identical to the subsequent injury. These data offer the basis for an attractive novel therapeutic approach against PDF toxicity.

HSP70 binding modulates detachment of Na-K-ATPase following energy deprivation in renal epithelial cells

The molecular mechanisms associated with reestablishment of renal epithelial polarity after injury remain incompletely delineated. Stress proteins may act as molecular chaperones, potentially modulating injury or enhancing recovery. We tested whether overexpression of heat shock protein 70 (HSP70) would stabilize Na-K-ATPase attachment to the cytoskeleton, under conditions of ATP depletion, and whether a direct association existed between Na-K-ATPase and HSP70 in cultured renal epithelial cells. LLC-PK1 cells were transfected with a tagged HSP70 (70FLAG) or vector alone (VA). Detachment of Na-K-ATPase was detected in Triton soluble lysate after ATP depletion. 70FLAG cells demonstrated a significant (P < 0.01) decrease in detachment of Na-K-ATPase after either 2 or 4 h of ATP depletion. Interactions between HSP70 and Na-K-ATPase were determined by coimmunoprecipitation of 70FLAG and Na-K-ATPase, by direct and competitive binding assays and by immunocytochemical localization. Binding of HSP70 and Na-K-ATPase increased dramatically following injury. Interactions were: 1) reversible; 2) reciprocal to changes in the HSP70 binding protein clathrin; and 3) present only when ATP turnover was inhibited in cell lysate, an established characteristic of HSP binding. These studies indicate that 1) overexpression of HSP70 is associated with decreased detachment of Na-K-ATPase from the cytoskeleton following injury; 2) HSP70 binds to Na-K-ATPase; and 3) binding of HSP70 to Na-K-ATPase is dynamic and specific, increasing in response to injury and decreasing during recovery. Interaction between the molecular chaperone HSP70 and damaged or displaced Na-K-ATPase may represent a fundamental cellular mechanism underlying maintenance and recovery of renal tubule polarity following energy deprivation.

The induction of heat shock protein-72 attenuates cisplatin-induced acute renal failure in rats

Induction of heat shock proteins (HSPs) is thought to play a protective role in ischaemic acute renal failure (ARF). However the role of HSPs in nephrotoxic ARF is not well explored. The aim of this study was to clarify the effects of the induction of HSP70s on cisplatin (CDDP) (6 mg/kg i.v.)-induced ARF in rats. Uranyl acetate (UA) or sodium arsenite (SA) were administered i.v. 14 days or 1 day respectively before CDDP injection to induce HSPs. Serum creatinine (SCr), tubular damage score and the numbers of apoptotic (TUNEL-positive) cells were examined 5 days after CDDP injection. The expression of HSP72, B-cell lymphoma gene product-2 (Bcl-2) and Bax were evaluated by Western blot analysis. We also investigated the effect of co-administration of chelerythrine chloride (Chel), which inhibits the induction of HSPs, with SA on the expression of HSP72 and nephrotoxicity. Pretreatment with UA or SA significantly induced renal HSP72 expression. Both UA and SA attenuated the CDDP-induced increase in SCr and tubular damage scores. Co-administration of Chel with SA abolished the SA-induced increment of HSP72 and the beneficial effects of SA. The protective effects of the induction of HSP72 were associated with an increased renal Bcl-2/Bax ratio and the reduction of TUNEL-positive cells in the outer stripe of outer medulla. Our findings suggest that HSP72 attenuates CDDP-induced nephrotoxicity. The protective effects of HSP72 are associated with an increased Bcl-2/Bax ratio and less apoptosis.

Liposomal delivery of heat shock protein 72 into renal tubular cells blocks nuclear factor-kappaB activation, tumor necrosis factor-alpha production, and subsequent ischemia-induced apoptosis

Heat shock protein 72 (HSP72) is a stress-inducible protein capable of protecting a variety of cells from toxins, thermal stress, and ischemic injury. The cytoprotective role and mechanism of action of HSP72 in renal cell ischemic injury remain unclear. To study this, HSP72 was introduced (liposomal transfer) or induced (thermal stress, 43 degrees Cx1 hour) in renal tubular cells (LLC-PK1) with Western blot confirmation. Cells were subjected to simulated ischemia 24 hours after liposomal HSP72 transfer or thermal stress, and the effect of HSP72 on nuclear factor-kappaB (NF-kappaB) activation (electrophoretic mobility shift assay and immunohistochemistry), IkappaBalpha production (Western blot), postischemic tumor necrosis factor-alpha (TNF-alpha) production (RT-PCR), and apoptosis (TUNEL assay) were determined. In separate experiments, the role of TNF-alpha in apoptosis was determined (anti-TNF-alpha neutralizing antibody). Results demonstrated that both liposomal transfer of HSP72 and thermal induction of HSP72 prevented NF-kappaB activation and translocation, TNF-alpha gene transcription, and subsequent ischemia-induced renal tubular cell apoptosis. Furthermore, TNF-alpha neutralization also inhibited ischemia-induced renal tubular cell apoptosis. These results indicate that liposomal delivery of HSP72 inhibits ischemia-induced renal tubular cell apoptosis by preventing NF-kappaB activation and subsequent TNF-alpha production. Further elucidation of the mechanisms of HSP-induced cytoprotection may result in therapeutic strategies that limit or prevent ischemia-induced renal damage.

Hsp27 associates with actin and limits injury in energy depleted renal epithelia

The purpose of the study was to determine whether Hsp27 interacts with actin and could protect against selected manifestations of injury from energy depletion in renal epithelia. LLC-PK1 cells were stably transfected to overexpress human Hsp27 tagged with green fluorescence protein (GFP). Transfected expression of the labeled Hsp27 did not reduce endogenous Hsp25 levels in the cells compared with either nontransfected cells or cells transfected with GFP alone used as the transfectant control (G). By fluorescence energy transfer (FRET) between GFP-tagged Hsp27 and rhodamine phalloidin-decorated actin, minimal interaction was found in uninjured control cells. In ATP-depleted cells, Hsp27 was associated closely with F-actin at lateral cell boundaries and with aggregated actin within the cell body. Less Hsp27 interaction with actin was found during recovery; but when adjusted for total phalloidin fluorescence, FRET between Hsp27 and F-actin did not change between 2-h ATP depletion and 4-h recovery. Where Hsp27 association with actin persisted during recovery, it was principally with the residual aggregates of actin in the cell body. Detachment of Na,K-ATPase from the cytoskeleton at 2-h ATP depletion was significantly less in Hsp27 cells compared with transfectant control G cells but not at 4-h ATP depletion. Detachment of ezrin from the cytoskeleton during ATP depletion was nearly complete and was not prevented in the Hsp27 cells. Protection of the Hsp27 cells was not attributable to preservation of cellular ATP levels. Hsp27 appears to have specific actions in renal epithelia subjected to energy depletion, including interacting with actin to preserve architecture in specific intracellular domains.

Heat shock protein 70 expression in neonatal rats after hypoxic stress

OBJECTIVES

The tissue damage due to hypoxia in newborns is to some extent age-dependent; organs of premature babies are more vulnerable to hypoxic insult than full-term neonates. The aim of this immunohistochemical study was to investigate the role of heat shock protein 70 (HSP70), a stress-inducible protein, in developing the response to hypoxia in premature newborns.

METHODS

Postnatal day-7 rats (corresponding to a human fetus of 32-34 weeks' gestation) and day-12 rats (corresponding to a full-term newborn infant) (n = 7) were subjected to mild hypoxia at 33 degrees C. Control rats (n = 7) for each group breathed room air for 4 h. After 4 h of recovery, the animals were killed, and brains, hearts and kidneys were removed for immunohistochemical staining.

RESULTS

Immunohistochemically, HSP70 expression was found to be induced in the hippocampus and myocardium after exposure to hypoxia. The level of HSP70 expression in the hippocampus after hypoxic stress was significantly higher in the 12-day rats than in the 7-day rats (p = 0.03). However, HSP70 expression in the myocardium did not show any significant difference between the two groups. In addition, no significant induction of HSP70 expression was apparent in the kidney of rats exposed to hypoxia or in any organ of the control animals.

CONCLUSIONS

We conclude that diminished HSP70 expression in the hippocampus of premature newborns may play a critical role in developing the response to hypoxic stress. However, HSP70 expression in the heart and the kidney after exposure to hypoxia did not appear to be related to fetal maturity.

Ischemic conditioning prevents Na,K-ATPase dissociation from the cytoskeletal cellular fraction after repeat renal ischemia in rats

Recent studies have suggested that heat shock proteins (HSPs) are involved in the restoration of the cytoskeletal anchorage of Na,K-ATPase after renal ischemia. To determine their role in ischemic conditioning, we investigated whether cytoskeletal Na,K-ATPase was stabilized during repeat ischemia concurrent with 25-kD and 70-kD HSPs induction. Anesthetized rats either underwent single unilateral renal ischemia or were conditioned with bilateral renal ischemia and, after 18 h of reflow, were then subjected to repeat unilateral renal ischemia. Renal cortex was harvested, and effects of single versus repeat ischemia were compared by Triton X-100 extraction, by immunohistochemistry, and by an in vitro assay of Na,K-ATPase association with isolated cytoskeletal fractions. In contrast to single ischemia, repeat ischemia did not result in increased Triton X-100 extractability of Na,K-ATPase. Levels of 25-kD and 70-kD HSPs were significantly induced by ischemic conditioning and redistributed into the cytoskeletal fraction after single and repeat ischemia. Immunohistochemistry also showed significant disruption of Na,K-ATPase within proximal tubules only after a single episode of ischemia, whereas repeat ischemia did not alter the pattern of restored Na,K-ATPase localization in conditioned renal cortex. The preserved association of Na,K-ATPase with the cytoskeletal fraction of conditioned renal cortex was effectively abolished in vitro by addition of antibodies against 25-kD or 70-kD HSP. These results suggest that 25-kD and 70-kD HSPs induced by ischemic conditioning stabilize the cytoskeletal anchorage of Na,K-ATPase during repeat renal ischemia.

HSP70 overexpression increases resistance of V79 cells to cytotoxicity of airborne pollutants, but does not protect the mitotic spindle against damage caused by airborne toxins

Exposure of Chinese hamster V79 cells to extracts of airborne pollutants induced formation of multipolar or incomplete mitotic spindles. To find out whether overexpression of the HSP70 chaperone protein could protect spindles against airborne toxins we constructed V79 cells stably transfected with an expression vector containing rat heat-inducible hsp70.1 gene under the control of a constitutive CMV promoter. When cells were incubated with extracts of airborne pollutants (5-20 microg/ml) no protective effect of the HSP70 protein against mitotic spindle damage was observed. Moreover, at 20 microg/ml of extracts of airborne toxins the frequency of mitotic malformations was even higher in HSP70-overexpressing cells than in control ones. Extracts of airborne pollutants of 50 microg/ml blocked the formation of mitotic figures both in control and HSP70-overexpressing cells and led to destruction of cell nuclei. However, the HSP70-overproducing cells exhibited higher survival rates when exposed to heat shock and airborne toxins than the control ones, as determined by MTT assay. This suggests that HSP70 overexpression-a frequent feature of cancer cells-should be considered as a factor facilitating survival of cells with damaged mitotic spindles and aberrantly segregated chromosomes.

Prevention of kidney ischemia/reperfusion-induced functional injury, MAPK and MAPK kinase activation, and inflammation by remote transient ureteral obstruction

Protection against ischemic kidney injury is afforded by 24 h of ureteral obstruction (UO) applied 6 or 8 days prior to the ischemia. Uremia or humoral factors are not responsible for the protection, since unilateral UO confers protection on that kidney but not the contralateral kidney. Prior UO results in reduced postischemic outer medullary congestion and leukocyte infiltration. Prior UO results in reduced postischemic phosphorylation of c-Jun N-terminal stress-activated protein kinase 1/2 (JNK1/2), p38, mitogen-activated protein kinase (MAPK) kinase 4 (MKK4), and MKK3/6. Very few cells stain positively for proliferating cell nuclear antigen after obstruction, indicating that subsequent protection against ischemia is not related to proliferation with increased numbers of newly formed daughter cells more resistant to injury. UO increases the expression of heat shock protein (HSP)-25 and HSP-72. The increased HSP-25 expression persists for 6 or 8 days, whereas HSP-72 does not. HSP-25 expression is increased in the proximal tubule cells in the outer stripe of the outer medulla postobstruction, prior to, and 24 h after ischemia. In LLC-PK(1) renal epithelial cells, adenovirus-expressed human HSP-27 confers resistance to chemical anoxia and oxidative stress. Increased HSP-27 expression in LLC-PK(1) cells results in reduced H(2)O(2)-induced phosphorylation of JNK1/2 and p38. In conclusion, prior transient UO renders the kidney resistant to ischemia. This resistance to functional consequences of ischemia is associated with reduced postischemic activation of JNK, p38 MAP kinases, and their upstream MAPK kinases. The persistent increase in HSP-25 that occurs as a result of UO may contribute to the reduction in phosphorylation of MAPKs that have been implicated in adhesion molecule up-regulation and cell death.

Regulation and localization of HSP70 and HSP25 in the kidney of rats undergoing long-term administration of angiotensin II

Various renal insults result in induction of heat shock protein (HSP) expression within the kidney. Some of the HSPs induced in that manner are postulated to have renoprotective effects via either chaperoning actions or antioxidative properties. We have previously reported that long-term angiotensin (Ang) II administration induces the expression of renal HSP32, also known as heme oxygenase-1 (HO-1). Here, we investigated the regulation of expression and localization of other HSPs, including HSP70, HSP25, and alphaB-crystallin, in the kidney of rats undergoing long-term administration of Ang II (0.7 mg. kg(-1). d(-1)). Immunoblot analysis demonstrated that Ang II increased renal expression of HSP70 and HSP25, as well as HO-1, but that expression of alphaB-crystallin was unaffected by this treatment. The Ang II-induced increase in renal HSP70 and HSP25 was dependent on the angiotensin type 1 receptor activation but not on hypertension per se. Immunohistochemistry revealed that HSP70 and HSP25 were expressed in the medullar regions and in the renal arterial wall in the kidney of control rats. After Ang II infusion, signals for HSP70, HSP25, and HO-1 proteins increased in intensity in the endothelium and medial smooth muscle of the renal artery. In addition, all of these HSPs were induced in proximal renal tubular epithelial cells from the same segments, suggesting that similar mechanisms are responsible for upregulating these HSPs. Our data show that Ang II infusion induces renal HSP70 and HSP25, as well as HO-1, and that Ang II can induce expression of these HSPs in renal cells in a pressor-independent manner.

Clinical application of hyperthermia combined with anticancer drugs for the treatment of solid tumors

BACKGROUND

Hyperthermia is one of the modalities used to treat various forms of malignancies, including esophageal, stomach, or rectal cancers.

METHODS

The basic mechanism of synergism between hyperthermia and anticancer drugs, as well as the clinical result of hyperthermia for the treatment of gastrointestinal malignancy, was reviewed.

RESULTS

Hyperthermia exerts a cytotoxic effect in combination with various mechanisms. Hyperthermia is applied in combination with chemotherapy and/or radiotherapy in the clinical setting. Among the anticancer drugs that are synergistic with hyperthermia is cisplatin, which is prevalent for clinical application. The mechanism of enhanced cytotoxicity of cisplatin includes increased intracellular drug accumulation, increased platinum-DNA adducts, and inhibition of DNA repair. At our institute, hyperthermochemoradiotherapy was conducted as a neoadjuvant therapy for either operative cases or as a palliative therapy for unresectable cases for esophageal and rectal cancers. In both situations, hyperthermochemoradiotherapy showed an excellent benefit in both the control of local recurrence and and in an improvement in patient survival. Regarding gastric cancer, the most popular application of hyperthermia was the intraoperative hyperthermic peritoneal lavage with cisplatin. This treatment modality demonstrated a better control of the disseminated lesion. Regarding the factors that influence thermosensitivity, in vitro experiments demonstrated the heat-shock proteins or tumor suppressor gene p53 to be related to thermosensitivity. In the clinical setting, these factors remain to be firmly established as predictive factors for thermosensitivity.

CONCLUSIONS

It is evident that hyperthermia was effective in the control of far-advanced gastrointestinal malignancies. When more reliable factors for the prediction of the treatment response can be established, the standard guidelines for the application of hyperthermia can then be made.

Heat shock prevents simulated ischemia-induced apoptosis in renal tubular cells via a PKC-dependent mechanism

Heat shock produces cellular tolerance to a variety of adverse conditions; however, the protective effect of heat shock on renal cell ischemic injury remains unclear. Protein kinase C (PKC) has been implicated in the signaling mechanisms of acute preconditioning, yet it remains unknown whether PKC mediates heat shock-induced delayed preconditioning in renal cells. To study this, renal tubular cells (LLC-PK1) were exposed to thermal stress (43 degrees C) for 1 h and heat shock protein (HSP) 72 induction was confirmed by Western blot analysis. Cells were subjected to simulated ischemia 24 h after thermal stress, and the effect of heat shock (delayed preconditioning) on ischemia-induced apoptosis (terminal deoxynucleotidyl transferase dUTP nick-end labeling) and B cell lymphoma 2 (Bcl(2)) expression (Western) was determined. Subsequently, the effect of PKC inhibition on HSP72 induction and heat stress-induced ischemic tolerance was evaluated. Thermal stress induced HSP72 production, increased Bcl(2) expression, and prevented simulated ischemia-induced renal tubular cell apoptosis. PKC inhibition abolished thermal induction of HSP72 and prevented heat stress-induced ischemic tolerance. These data demonstrate that thermal stress protects renal tubular cells from simulated ischemia-induced apoptosis through a PKC-dependent mechanism.

Perinatal expression of heat shock proteins HSC 70 and HSP 70 in neural and non neural tissues of the piglet

Stress of different kinds during early perinatal life can result in severe consequences for further development. To determine possible involvement of heat shock proteins in brain development, the expression of HSC 70 and HSP 70 was determined in brain regions (cerebellum, cortex, hippocampus, hypothalamus and striatum) and non neural tissues (liver, lungs and kidneys) at birth and during early development of the piglet. In brain regions, HSC 70 expression was decreased during the few hours following birth. With the exception of cortex, hippocampus and kidney where a decrease of expression was observed, HSP 70 did not show significant changes during early development. These results are discussed in terms of using the piglet model of development to study the effect of different kinds of stress like hypoxia or temperature changes on brain development.

Heat shock protein-70 repairs proximal tubule structure after renal ischemia

BACKGROUND

Recent studies have suggested a role of heat shock protein (HSP)-70 in cytoskeletal repair during cellular recovery from renal ischemia. The aim of this study was to test the hypothesis that HSP-70 interacts in vitro with cytoskeletal elements obtained from rat renal cortex during early reflow after renal ischemia.

METHODS

Cellular proteins were fractionated into cytoskeletal pellets and noncytoskeletal supernatants by Triton X-100 extraction of rat renal cortex obtained after 15 minutes or 18 hours of reflow after 45 minutes of renal ischemia, or from controls. Aliquots of isolated pellets were coincubated with aliquots of isolated supernatants in different combinations. A repeat Triton extraction was performed, and differential distribution of Na, K-ATPase or HSP-70 was assessed by Western blots and densitometric analysis.

RESULTS

Coincubation of cytoskeletal pellets obtained during early reflow after renal ischemia (exhibiting severe injury of the cytoskeletal anchorage of Na,K-ATPase) and noncytoskeletal supernatant obtained during later reflow (showing high HSP expression) resulted in specific translocation of HSP-70 from the supernatant into the pellet, functionally associated with dose-dependent stabilization of Na,K-ATPase within this cytoskeletal fraction. These effects could be reproduced by incubation with purified HSP-70 and were abolished by the addition of anti-HSP-70 antibodies.

CONCLUSION

These data support the hypothesis that HSP-70 interacts with cytoskeletal elements during the restoration of proximal tubule cell structure and polarity after renal ischemia. This experimental approach represents a new in vitro assay to study further the role of HSP in cellular repair.

Molecular chaperones in the kidney: distribution, putative roles, and regulation

Molecular chaperones are intracellular proteins that prevent inappropriate intra- and intermolecular interactions of polypetide chains. A specific group of highly conserved molecular chaperones are the heat shock proteins (HSPs), many of which are constitutively expressed but most of which are inducible by diverse (in some cases specific) stress factors. HSPs, either alone or in cooperation with "partner" chaperones, are involved in cellular processes as disparate as correct folding and assembly of proteins, transport of proteins to specific intracellular locations, protein degradation, and preservation and restructuring of the cytoskeleton. The characteristic distribution of individual HSPs in the kidney, and their response to different challenges, suggests that a number of HSPs may fulfill specific, kidney-related functions. HSP72 and the osmotic stress protein 94 (Osp94) appear to participate in the adaptation of medullary cells to high extracellular salt and urea concentrations; the small HSPs (HSP25/27 and crystallins) may be involved in the function of mesangial cells and podocytes and contribute to the volume-regulatory remodeling of the cytoskeleton in medullary cells during changes in extracellular tonicity. HSP90 contributes critically to the maturation of steroid hormone receptors and may thus be a critical determinant of the aldosterone sensitivity of specific renal epithelial cells. Certain HSPs are also induced in various pathological states of the kidney. The observation that the expression of individual HSPs in specific kidney diseases often displays characteristic time courses and intrarenal distribution patterns supports the idea that HSPs are involved in the recovery but possibly also in the initiation and/or maintenance phases of these disturbances.