Effect of glutamine on heat-shock-induced mRNA and stress proteins

Acute heat stress-indued apoptosis in mouse skeletal muscle is not associated with alteration of glutamine homeostasis

We previously demonstrated that exposing mice to heat causes functional and ultrastructural mitochondrial alterations and apoptosis in skeletal muscle. Emerging evidence indicates that glutamine (Gln) deprivation may increase cell susceptibility to apoptosis whereas Gln supplementation may protect cells against heat stress. In this study, we investigated the effect of short-term Gln treatment on heat-induced changes in mouse skeletal muscle. Male mice received vehicle, low-dose Gln (100 mg/kg/d) or high-dose Gln (300 mg/kg/d) through daily gavage for 10 days before a heat exposure test. During heat exposure, mice displayed a hyperthermic response and no significant differences in peak core body temperature were noted across the three groups. Neither heat exposure nor pretreatment with low-dose or high-dose Gln significantly affected Gln concentrations in plasma and gastrocnemius muscles. Heat-exposed mice had significantly higher caspase 3/7 levels in gastrocnemius muscle compared to unexposed controls. Heat exposure significantly increased ROS production and mitochondrial fragmentation and decreased mitochondrial membrane potential in flexor digitorum brevis muscle. These changes were not affected by low- or high-dose Gln pretreatment. Together, acute heat stress did not disrupt Gln homeostasis in mouse skeletal muscle and Gln supplementation did not protect mouse skeletal muscle against heat-induced injury. The results of this study do not support a role of Gln in heat-induced skeletal muscle apoptosis.

Nutritional considerations to counteract gastrointestinal permeability during exertional heat stress

Intestinal barrier integrity and function are compromised during exertional heat stress (EHS) potentially leading to consequences that range from minor gastrointestinal (GI) disturbances to fatal outcomes in exertional heat stroke or septic shock. This mini-review provides a concise discussion of nutritional interventions that may protect against intestinal permeability during EHS and suggests physiological mechanisms responsible for this protection. Although diverse nutritional interventions have been suggested to be protective against EHS-induced GI permeability, the ingestion of certain amino acids, carbohydrates, and fluid per se is potentially effective strategy, whereas evidence for various polyphenols and pre/probiotics is developing. Plausible physiological mechanisms of protection include increased blood flow, epithelial cell proliferation, upregulation of intracellular heat shock proteins, modulation of inflammatory signaling, alteration of the GI microbiota, and increased expression of tight junction (TJ) proteins. Further clinical research is needed to propose specific nutritional candidates and recommendations for their application to prevent intestinal barrier disruption and elucidate mechanisms during EHS.

Lipid and Metabolite Profiling of Serpula lacrymans Under Freezing Stress

Basidiomycete fungus Serpula lacrymans is one of the most dangerous indoor fungus causing dry rot of timber. The physiology of this fungus deserves more attention as a basis for development of methods of dry rot treatment. We observed an increase in the freezing resistance of S. lacrymans after pre-cultivation of mycelia at elevated temperatures. To examine the biochemical mechanisms underlying this phenomenon the lipid composition and metabolite profiling of mycelia subjected to freezing and thawing were investigated. An analysis is made of the growth rate and metabolism of "daughter" cultures derived from a frozen mycelia. According to the results, sphingolipids and water-soluble metabolites such as mannitol, glycerol, sugar alcohols, some amino- and organic acids are able to function as protective compounds providing a cross-resistance between heat shock and freeze-thaw stress in S. lacrymans.

Evaluation of general stress, detoxification pathways, and genotoxicity in rainbow trout exposed to rare earth elements dysprosium and lutetium

Rare earth elements (REEs) have been recently identified as emergent contaminants because of their numerous and increasing applications in technology. The impact of REEs on downstream ecosystems, notably aquatic organisms, is of particular concern, but has to date been largely overlooked. The purpose of this study was thus to evaluate the toxicity of lanthanide metals, lutetium (Lu) and dysprosium (Dy) in rainbow trout after 96 h of exposure. The lethal concentration (LC50) was determined and the expression of 14 genes involved in different pathways such as oxidative stress, xenobiotic detoxification, mitochondrial respiration, DNA repair, protein folding and turnover, inflammation, calcium binding and ammonia metabolism were quantified in surviving fish. In parallel, lipid peroxidation (LPO), DNA damage (DSB), metallothionein level (MT) and cyclooxygenase activity (COX) were examined. The acute 96 h-LC₅₀ data revealed that Lu was more toxic than Dy (1.9 and 11.0 mg/L, respectively) and was able to affect all investigated pathways by changing the expression of the studied genes, to the exception of superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST). It also induced a decrease in DNA repair at concentrations 29 times below the LC₅₀. This suggests that Lu could trigger a general stress to disrupt the cell homeostasis leading to genotoxicity without promoting oxidative stress. However, Dy induced modulation in the expression of genes involved in the protection against oxidative stress, detoxification, mitochondrial respiration, immunomodulation, protein turnover and an increase in the DNA strand breaks at concentrations 170 times lower than LC₅₀. Changes in mRNA level transcripts could represent an early signal to prevent against toxicity of Dy, which exhibited inflammatory and genotoxic effects. This study thus provides useful knowledge enhancing our understanding of survival strategies developed by rainbow trout to cope with the presence of lanthanides in the environment.

Intestinal growth and morphology is associated with the increase in heat shock protein 70 expression in weaning piglets through supplementation with glutamine

The objectives of this study were to determine the effects of oral Gln supplementation on growth performance, intestinal morphology, and expression of heat shock protein (Hsp) 70 in weaning piglets. A total of 65 piglets after weaning at 21 d of age (d 0) were used in this experiment. Five piglets were randomly selected and euthanized initially at d 0 to determine baseline values for the expression of Hsp70 in the small intestine. The remaining piglets were randomly assigned to 1 of 2 treatments and received 0 or 1 g of oral Gln/kg of BW every 12 h. After piglets were humanely killed at d 3, 7, and 14 postweaning, the duodenum, jejunum, and ileum of piglets were sampled to evaluate intestinal morphology and the expression and localization of Hsp70. The results indicated that oral Gln supplementation increased plasma concentrations of Gln compared with those in control piglets (P < 0.05). Average daily gain and ADFI were greater in piglets orally supplemented with Gln than in control piglets during the whole period (P < 0.05). The incidence of diarrhea in piglets orally supplemented with Gln was 24% less than (P = 0.064) that in control piglets at 8 to 14 d after weaning. The weights of the jejunum and ileum were greater in piglets orally supplemented with Gln compared with those of control piglets relative to BW on d 14 postweaning (P < 0.05). The villus height and the villus height:crypt depth ratio in the jejunum and the ileum were greater in piglets receiving oral Gln on d 14 postweaning (P < 0.05) than in control piglets. These results indicate that Gln supplementation can influence the intestinal morphology of weaned piglets. The expression of hsp70 mRNA and Hsp70 proteins in the duodenum and jejunum was greater in piglets supplemented with Gln than in control piglets (P < 0.05). However, Gln supplementation had no effect on the expression of hsp70 mRNA and Hsp70 proteins in the ileum. Moreover, the localization of Hsp70 in the cytoplasm indicated that Hsp70 has a cytoprotective role in epithelial cell function and structure. These results indicate that Gln supplementation may be beneficial for intestinal health and development and may thus mitigate diarrhea and improve growth performance. The protective mechanisms of Gln in the intestine may be associated with the increase in Hsp70 expression.

Attenuation of lipopolysaccharide-mediated left ventricular dysfunction by glutamine preconditioning

OBJECTIVE

Myocardial dysfunction is often seen during the inflammatory response to major surgery at 4 to 6h postoperatively. The aim of this study was to investigate the effect of glutamine pretreatment, as a means of preconditioning, on lipopolysaccharide-induced myocardial dysfunction.

METHODS

C57BL/6 mice were randomized into four groups: Control; lipopolysaccharide; glutamine plus lipopolysaccharide; and Quercetin, an inhibitor of heat shock protein synthesis plus glutamine and lipopolysaccharide. Left ventricular function was assessed at 6h following lipopolysaccharide (LPS) insult by invasive hemodynamics. Heat shock protein (HSP)72 in heart tissue was determined by Western immunoblot at 12h after glutamine administration.

RESULTS

Administration of lipopolysaccharide resulted in significant decrease in left ventricular end systolic pressure (LVESP) (69.1 +/- 2.52 mm Hg versus 106.3 +/- 3.36 mm Hg in controls), reduced dP/dtmax (4704.1 +/- 425.31 mm Hg/s versus 9389.8 +/- 999.4 mm Hg/s in controls), and the increase in left ventricular end diastolic pressure (LVEDP) (5.10 +/- 0.28 mm Hg versus 2.16 +/- 0.27 mm Hg in controls) (P < 0.05). Peritoneal injection of 25 g/kg of glutamine 12 h prior to lipopolysaccharide exposure induced HSP72 expression in heart tissues and attenuated lipopolysaccharide-induced left ventricular dysfunction: LVESP 85.94 +/- 3.8 mm Hg (P < 0.05), dP/dtmax 8331 +/- 425 mm Hg (P < 0.05), LVEDP 2.32 +/- 0.23 mm Hg (P < 0.01). Quercetin partially attenuated glutamine induced HSP72 expression and blocked the protective response of glutamine.

CONCLUSION

These data demonstrate that cardioprotection with glutamine is associated with induction of HSP72 and may be an approach to activating the preconditioning response in the heart in clinical practise.

Glutamine induces heat-shock protein-70 and glutathione expression and attenuates ischemic damage in rat islets

BACKGROUND

The transplantation of isolated islets is believed to be an attractive approach for cure of diabetes mellitus. Heat-shock protein (HSP70), which plays a vital role in cellular protection, has been detected in various tissues subjected to stress. Glutamine (GLN) is an important cellular fuel and an essential precursor for the antioxidant glutathione (GSH). It is believed to enhance cellular survival against a variety of stressful stimuli through HSP70. Thus, we performed this study to examine the hypothesis that preoperative GLN administration induces HSP70 and GSH expression before islet transplantation attenuating ischemic damage to rat islets.

METHODS

Adult male Sprague-Dawley (SD) rats were randomly divided into two groups according to the administration of GLN after islet isolation. Group A served as the controls, receiving no GLN. Group B islet cells were cultured with L-GLN (10 mmol/L) supplementation for 24 hours. The GSH levels were measured in islet cells. Both HSP70 and proteins related to apoptosis were analyzed in islet cells by Western blots. Isolated rat islets were cultured with interleukin (IL)-1beta. Nitrite production was measured using the Griess reagent.

RESULTS

The GSH levels were significantly elevated in the glutamine-treated group. HSP70 expression in islets treated with GLN was markedly stronger compared with the control group. The basal Bcl-2 expression was markedly increased by GLN treatment. The GLN-treated group showed attenuated IL-1beta-induced injury in association with NO production.

CONCLUSION

These results suggested that preoperative GLN administration induced HSP70 and GSH expressions before islet transplantation, thus attenuating IL-1beta-induced injury in association with NO production and apoptosis, which might be potential tool to mitigate the ischemic damage to islet cells and the early inflammation at the site of implantation through a self-protective mechanism.

Exogenous glutamine: The clinical evidence

We know that critically ill patients suffering from undernutrition with a limited nutritional reserve have a poorer outcome. Furthermore, having a low body mass index has been shown to be an independent predictor of excess mortality in multiple organ failure. Therefore, nutritional support has gained increasing interest in critical illness with the hope of preventing or attenuating the effects of malnutrition. A negative nitrogen balance is the characteristic metabolic feature in critical illness, with the major protein loss derived from skeletal muscle. In particular, glutamine concentrations are rapidly reduced in plasma and muscle. Over the last 20 yrs or so, increasing evidence is emerging to support the use of glutamine supplementation in critical illness. Clinical trials have found a mortality and morbidity advantage with glutamine supplementation. The advantage appears to be greater the more glutamine is given and greater again when given parenterally. Various modes of action have been postulated. Glutamine seems to have an effect on the immune system, antioxidant status, glucose metabolism, and heat shock protein response. However, the benefit of exogenous glutamine on morbidity and mortality is not universally accepted. This review critically appraises the current clinical evidence regarding glutamine supplementation in critical illness.

Anti-inflammatory and antinecrotic effects of the volatile anesthetic sevoflurane in kidney proximal tubule cells

Renal ischemia-reperfusion (IR) injury is a major clinical problem without effective therapy. We recently reported that volatile anesthetics protect against renal IR injury, in part, via their anti-inflammatory properties. In this study, we demonstrate the anti-inflammatory and antinecrotic effects of sevoflurane in cultured kidney proximal tubule cells and probed the mechanisms of sevoflurane-induced renal cellular protection. To mimic inflammation, human kidney proximal tubule (HK-2) cells were treated with tumor necrosis factor-α (TNF-α; 25 ng/ml) in the presence or absence of sevoflurane. In addition, we studied the effects of sevoflurane pretreatment on hydrogen peroxide (H2O2)-induced necrotic cell death in HK-2 or porcine proximal tubule (LLC-PK1) cells. We demonstrate that sevoflurane suppressed proinflammatory effects of TNF-α evidenced by attenuated upregulation of proinflammatory cytokine mRNA (TNF-α, MCP-1) and ICAM-1 protein and reduced nuclear translocation of the proinflammatory transcription factors NF-κB and AP-1. Sevoflurane reduced necrotic cell death induced with H2O2in HK-2 cells as well as in LLC-PK1cells. Sevoflurane treatment resulted in phosphorylation of prosurvival kinases, ERK and Akt, and increased de novo HSP-70 protein synthesis without affecting the synthesis of HSP-27 or HSP-32. We conclude that sevoflurane has direct anti-inflammatory and antinecrotic effects in vitro in a renal cell type particularly sensitive to injury following IR injury. These mechanisms may, in part, account for volatile anesthetics' protective effects against renal IR injury.

Reduced stress tolerance of glutamine-deprived human monocytic cells is associated with selective down-regulation of Hsp70 by decreased mRNA stability

In critically ill patients, clinicians observe a reverse correlation of survival and a decreased plasma concentration of the most abundant free amino acid, glutamine (Gln). However, in this context, the role of Gln remains largely elusive. Gln is used as an energy substrate by monocytes. Gln deprivation of these cells results in an increased susceptibility to cell stress and apoptosis, as well as in a reduced responsiveness to pro-inflammatory stimuli. We performed a systematic study to elucidate the molecular mechanism by which Gln depletion affects the heat stress response of the monocytic cell line U937. Proteomic analysis revealed that Gln depletion was associated with specific changes in the protein expression pattern. However, the overall level of tRNA-bound Gln remained unaffected. The stress protein heat shock protein (Hsp) 70 showed the highest reduction in protein synthesis. This was due to enhanced mRNA decay during Gln starvation while the transcriptional and the translational control of Hsp70 expression remained unchanged. A physiological Gln concentration and above was found to be necessary for maximum Hsp70 accumulation upon heat shock. Thus, the study shows a specific link between Gln metabolism and the regulation of heat shock proteins.

Anti-apoptotic effects of L-glutamine-mediated transcriptional modulation of the heat shock protein 72 during heat shock

BACKGROUND & AIMS

During physiologic stress, L-glutamine becomes conditionally essential. Its deficiency results in altered epithelial barrier competence, bacterial translocation, and decreased survival. L-glutamine may attenuate these effects by modulating heat shock protein expression, a well-described effect in vitro. We sought to characterize L-glutamine-dependent transcriptional regulation in heat-shocked intestinal cells and to determine its physiologic relevance.

METHODS

IEC-18 and H4 intestinal cells were used. Heat shock protein 72 (Hsp72) gene expression was determined by Northern blotting and luciferase assays. Heat shock factor-1 (HSF-1) activation was assessed by electromobility shift assay, Western blotting, and HSF-1 minimal promoters. Phosphorylation and trimerization of HSF-1 were determined by immunoprecipitation and native nonreducing gradient polyacrylamide gel electrophoresis (PAGE). Camptothecin-induced apoptosis was monitored using caspase-3 and poly (ADP-ribose) polymerase [PARP]-specific antibodies and DNA Elisa +/- Hsp72 siRNA.

RESULTS

L-glutamine specifically augmented Hsp72 transcript abundance and HSF-1 DNA binding during heat shock. No glutamine-dependent differences in HSF-1 phosphorylation, trimerization, nuclear localization during heat shock, or HSF-1 minimal promoter activity were observed. Nevertheless, the presence of L-glutamine was an important determinant of wild-type Hsp72 promoter transcriptional activation. Reduced Hsp72 was associated with increased camptothecin-induced caspase-3 and PARP cleavage in glutamine-deficient cells. siRNA treated cells were less resistant to camptothecin.

CONCLUSIONS

Taken together, the data suggest that glutamine does not affect the classical pathway of HSF-1 activation and that glutamine-dependent upstream trans -factor binding elsewhere in the Hsp72 promoter or coactivator recruitment may determine Hsp72 abundance. L-glutamine potentiation of Hsp72 is associated with increased epithelial resistance to apoptotic injury.

Glutamine Analogues As Adjunctive Therapy for Infectious Diarrhea

Glutamine is the major fuel for the gut as well as for many cells in the immune system that becomes conditionally essential during catabolic states. Glutamine supplementation improves intestinal mucosal repair and function. Glutamine, even at high doses, is without side effects and is well tolerated. Though unstable in solution, this is overcome by creating stable dipeptides such as alanyl-glutamine. In HIV-positive patients with wasting, glutamine enhances intestinal absorptive function and weight gain. Glutamine enhances sodium and water absorption in a rabbit model of cholera and Cryptosporidium-infected piglet intestine. Both glutamine and alanyl-glutamine have recently proven effective in a bovine model of Cryptosporidium as well. Finally, a rat model of cholera toxin-induced diarrhea also showed that alanyl-glutamine enhanced water and electrolyte intestinal absorption even better than the traditional glucose solutions. Clearly glutamine and its stabler derivatives hold promise for enhancing repair of mucosal injury by a wide range of infections or toxic agents, and hence have great potential as a new oral rehydration and nutrition therapy for patients with enteric infection, malnutrition, or chemotherapy- or radiation-induced enteritis.

Preoperative glutamine administration induces heat-shock protein 70 expression and attenuates cardiopulmonary bypass-induced inflammatory response by regulating nitric oxide synthase activity

BACKGROUND

Heat-shock protein 70 (HSP70) plays a major role in the pathophysiology of inflammation, and the induction of HSP70 before the onset of inflammation can reduce organ damage through a self-protective system. Glutamine is known to be an inducer of HSP70, and its preoperative administration seems useful in attenuating cardiopulmonary bypass (CPB)-induced inflammatory response.

METHODS AND RESULTS

Adult male Sprague-Dawley rats (group G, received 100 mg/kg of glutamine via the right jugular vein 3 times per day for 1 week and just before the initiation of CPB; group C served as control) underwent CPB (60 minutes, 100 mL/kg per minute, 34 degrees C) and were killed 3 hours after the termination of CPB. Group G showed significantly lower plasma concentrations of interleukin-6 and interleukin-8 after CPB termination. Myocardial and respiratory damages were significantly attenuated in group G, as evidenced by Langendorff perfusion, respiratory index, and neutrophil adherence. HSP70 expressions in the heart, lung, and liver were detected only in group G before CPB and were markedly stronger in group G 3 hours after CPB termination. Although plasma nitrate+nitrite concentrations were not significantly different between the groups, endothelial-constitutive nitric oxide synthase (NOS) activity was markedly preserved and inducible NOS activity was markedly attenuated in the tissues of group G.

CONCLUSIONS

These results suggest that preoperative glutamine administration induces HSP70 expression before CPB and attenuates CPB-induced inflammation by regulating NOS activity, which may be a prospective management for conferring tolerance to CPB-induced inflammatory response through a self-protective mechanism.

Ammonia aggravates stress-induced gastric mucosal oxidative injury through the cancellation of cytoprotective heat shock protein 70

The relationship between Helicobacter pylori colonization and the formation of stress-induced gastric mucosal injury remains unknown. Since ammonia (NH(3)) is known as one of the injurious factors in H. pylori-colonized gastric mucosa, the present study is designed to investigate the level of stress-induced gastric mucosal oxidative injury with or without intragastric NH(3) overloading. To apply emotional stress, the communication box paradigm was used in the mouse model. Mice (C57BL/6, male) were pretreated with distilled water (responder-H(2)O) or 0.01% NH(3) (responder-NH(3)) through a gastric tube once a day for a week. Emotional stress was then applied to the responder mice for 3 h per day for 3 d by watching and hearing the behavior of the sender mice subjected to electric shocks to the feet (2 mA, 10 s, 50 s interval). After the communication box protocol, the tissue MPO activity, the contents of TBA-reactive substances (TBARS), and the level of gastric mucosal HSP70 were examined. Responder-NH(3) mice developed more severe gastric lesions than the responder-H(2)O subjects. MPO activity and TBARS contents were enhanced significantly in the responder-NH(3) group compared with the responder-H(2)O subjects. Although the contents of HSP70 in the gastric mucosa increased in the responder-H(2)O group compared with the control-H(2)O animals, they were significantly attenuated in the responder-NH(3) mice. Excess intragastric NH(3) was able to enhance the formation of emotional stress-induced gastric mucosal lesions. This injury may be associated with the enhanced production of oxygen free radicals from accumulated neutrophils under the NH(3)-mediated cancellation of gastric mucosal cytoprotective HSP70.

Acute enteral glutamine infusion enhances heme oxygenase-1 expression in human duodenal mucosa

The heat shock protein, heme oxygenase-1 (HO-1), contributes to the protection of the intestine. Some experimental models suggest that induction of HO-1 by glutamine may contribute to the preservation of intestinal mucosa. The effect of an enteral infusion of glutamine for 6 h on HO-1 expression in duodenal mucosa was studied in healthy men and women and compared with an isonitrogenous mixture of amino acids. After enteral infusion, endoscopic duodenal biopsies were performed and either fixed in formalin for immunohistochemistry or frozen for HO-1 mRNA analysis by reverse transcriptase-polymerase chain reaction. Histologic examination revealed that HO-1 was constitutively expressed in intestinal epithelial cells (IEC), and that glutamine increased the grade of HO-1 immunostaining (P </= 0.01). Glutamine also increased the percentage of HO-1 immunoreactive lamina propria cells (LPC, 10.5 vs. 7.5%, P </= 0.05). Glutamine significantly increased HO-1 mRNA expression compared with control amino acids: median (range) 156 (102-182) vs. 100 (68-179)%, P </= 0.05. The mRNA level for HO-1 was correlated with the percentage of immunoreactive LPC (r = 0.55, P = 0.017) and the grade of immunostaining in IEC (r = 0.51, P = 0.030). In conclusion, glutamine enhanced HO-1 mRNA and protein expression in human duodenal mucosa. These data support further evaluation of the effects of glutamine on intestinal HO-1 during states of intestinal inflammation.

Glutamine and heat shock protein expression

The most basic mechanism of cellular protection involves the expression of a highly conserved family of essential proteins, known as heat shock or stress proteins (HSPs). The expression of these proteins after a sublethal insult can induce "stress tolerance" and protect against a subsequent stress that otherwise would be lethal. Experimental data have shown that preinduction of the heat stress response can provide marked protection against many forms of cellular injury, including ischemia and reperfusion, lung injury, and shock. However, induction of HSPs to improve outcome in human disease has not been exploited because laboratory induction agents are themselves toxic and not clinically relevant. Many researchers have found that glutamine (GLN), a conditionally essential amino acid, can enhance stress-induced HSP expression in vitro and improve cell survival against a variety of stressful stimuli. Further, recent data from me and my colleagues indicate that a single dose of intravenous GLN can enhance HSP expression, decrease end-organ injury, and enhance survival from septic shock in the intact rat. Thus GLN, which is beneficial in many settings of critical illness and injury, may be a clinically applicable enhancer of HSP expression. These results indicate that GLN could be used to enhance HSP expression and attenuate end-organ injury in situations when a major clinical stress is anticipated, such as before major surgical procedures (e.g., cardiac, vascular, and transplantation) or in the critically ill.

Glutamine depletion impairs cellular stress response in human leucocytes

During sepsis and major trauma the blood glutamine (Gln) level is reduced. The administration of Gln can improve the outcome of these patients. However, the mechanism of this beneficial effect of Gln is poorly understood. In the course of critical illness leucocytes are confronted with cytotoxic inflammatory mediators. To protect themselves against these factors, cells express heat shock proteins (HSP). Previous studies have shown that the expression of the major inducible HSP (HSP70) is improved by high Gln concentrations above 4 mM. In this study we investigated whether Gln depletion, such as observed during critical illness, has an effect on HSP70 expression. Human lymphocytes exposed for 2 h to 42 degrees C showed a 3-fold increase in HSP70 expression (P<0.01). A preceding Gln starvation period over 3 days had no influence on this increase. However, when Gln is reduced during the stress response, HSP70 expression is impaired. A reduction of Gln from 0.5 mM (physiological) to 0.125 mM (pathological) led to a 40% lower HSP70 level (P<0.002). In contrast, increasing Gln concentrations (up to 2 mM) had only minor stimulatory effects (about 15%). This Gln-dependency of heat mediated HSP70 expression was observed in resting as well as proliferating lymphocytes. Our data indicate that during periods of reduced plasma Gln levels the stress response of human lymphocytes is impaired. Thus, Gln may be essential to minimize the susceptibility of leucocytes to cytotoxic inflammatory mediators. This is a new aspect of the protective effect of Gln supplementation in critically ill patients.

A novel heat stress-responsive gene in the marine diatom Chaetoceros compressum encoding two types of transcripts, a trypsin-like protease and its related protein, by alternative RNA splicing

We investigated the change of mRNA expression patterns in the laboratory-grown diatom Chaetoceros compressum under heat-stress conditions by mRNA arbitrarily primed (RAP) RT-PCR. Cells grown at 20 degrees C were subjected to heat treatment at 30 degrees C for 15 min and subsequently maintained at 20 degrees C for 8 h. Four genes including HI-5 were detected as heat stress-responsive genes by fingerprint analysis of RAP RT-PCR. Cloning for full-length cDNA sequences of HI-5 transcripts and related genomic DNA analysis revealed that two types of mRNA, HI-5a and HI-5b, were transcribed from the single HI-5 gene. While the HI-5a protein contained a catalytic domain characteristic to trypsin-like proteases, the HI-5b protein lacked this domain due to an insertion in the associated mRNA of 112 nucleotides; this insertion sequence contained a stop codon near the central region. Quantitative RT-PCR was performed to investigate the changes in expression levels of the two types of mRNA following heat treatment. The HI-5b transcripts were constitutively expressed in both unstressed and heat-stressed cells. In contrast, the number of HI-5a transcripts markedly increased in cells immediately after heat stress, reaching levels 19-fold higher at 8 h after heat stress than that in unstressed cells. These results suggest that RNA splicing plays a key role in heat stress-dependent expression of the HI-5a and HI-5b transcripts from the single HI-5 gene in the diatom.

Alanyl-glutamine dipeptide does not affect hemodynamics despite a greater increase in myocardial heat shock protein 72 immunoreactivity in endotoxemic sheep

The possible beneficial effect of supplemental glutamine (Gln) in critically ill patients has been suggested to be mediated by the induction of the cytoprotective heat shock proteins (HSP)32 and HSP72. There is evidence that HSP72 and HSP32 have opposite effects on the hemodynamic situation during endotoxemia. Therefore, the effect of Gln supplementation on the cardiovascular system is not clear. We investigated the effect of alanyl-Gln (Ala-Gln) dipeptide on cardiovascular function in healthy and endotoxemic sheep. Ten sheep catheterized for chronic studies received Ala-Gln 700 mg/(kg x d) [equal to 470 mg/(kg x d)Gln] on 4 consecutive days, and 10 sheep received NaCl (9 g/L) as the control solution. On d 4, four sheep of each group were killed and myocardial samples were taken for immunohistochemistry. The remaining sheep received a continuous infusion of endotoxin [Salmonella typhosa, 10 ng/(kg x min)]. Hemodynamic parameters were measured before application of Ala-Gln or the control solution, and during endotoxemia. Myocardial HSP72 immunoreactivity was determined by immunohistochemistry. After 24 h of endotoxemia, the sheep exhibited a hyperdynamic circulation. No difference was found in the hemodynamic parameters between treatment and control group. Ala-Gln treated sheep had a greater increase in myocardial HSP72 immunoreactivity compared with controls after (P < 0.05) but not before endotoxemia. In summary, Ala-Gln increased HSP72 immunoreactivity after endotoxemia, but did not alter hemodynamic parameters. Thus, Ala-Gln supplementation does not seem to aggravate the hyperdynamic circulation in endotoxemic shock.

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.

Glutamine reduces heat shock-induced cell death in rat intestinal epithelial cells

Glutamine supplementation is beneficial for preventing intestinal atrophy and maintaining mucosal functions in metabolically stressed patients. The mechanisms by which glutamine prevents mucosal atrophy remain unclear. In particular, the role of glutamine in the survival of cells under stress is unknown. Intestinal epithelial cells (IEC-6) were cultured in media with or without supplementation of L-glutamine. A low concentration of L-glutamine (1.0 mmol/L) was sufficient to minimize the percentage of floating cells under basal conditions. Heat shock at 43 degrees C for 90 min decreased (P < 0. 001) the number of attached cells, while increasing (P < 0.001) the number of floating cells, which is a measurement of the extent of cell death in these cultures. Glutamine enhanced attached cell count and diminished heat shock-induced cell death in a dose-dependent manner. Of note, 2 mmol/L was suboptimal in both respects, thus indicating that heat-shocked cells require higher concentrations of glutamine for optimal cell survival. Maximal effect was achieved with 8 mmol/L glutamine, which increased (P < 0.001) cell growth (indicated by the number of attached cells) and diminished (P < 0. 001) cell death (indicated by the number of floating cells). Further increase of L-glutamine concentration to 12 or 20 mmol/L did not provide additional benefit in minimizing cell death. Heat shock protein 70 (hsp 70) mRNA was induced by heat shock only in cultures supplemented with L-glutamine, and the induction was more consistent and greater in cultures containing higher concentrations of glutamine. Thus, glutamine supplementation reduced heat shock-induced cell death. This effect, together with the maintenance of cell growth, may play a key role in the prevention of intestinal mucosal atrophy.

Low glutamine concentrations induce phenotypical and functional differentiation of U937 myelomonocytic cells

L-Glutamine is the most abundant free amino acid of the human body and is essential for the culture of many cell types. Clinically, reduction of glutamine by administration of glutaminase or the use of glutamine analogs is a common therapy for patients with acute lymphocytic leukemia. In the current study, we investigated the influence of glutamine concentrations on the human myelomonocytic cell line U937. Decreasing the glutamine concentration evoked a reduction in DNA synthesis (R2 = 0.9885, P < 0.0001), increased cell volume (P < 0.01) and the cytoplasm/nuclear ratio, and enhanced the development of vacuoles but did not influence cell viability. Culturing cells in reduced concentrations of glutamine augmented the percentage of cells expressing CD64 (Fc receptor for IgG/FcgammaRI, P < 0.01), CD11b (complement receptor type 3/CR3, P < 0.001) and CD71 (transferrin receptor, P < 0.05). The percentage of U937 cells expressing CD23 (low affinity receptor for IgE/FcepsilonRII) was increased at low concentrations of glutamine at both the protein (P < 0.01) and mRNA levels. The percentage of U937 cells phagocytizing opsonized E. coli (P < 0.001) or latex particles (P < 0.001) was enhanced by lowering the glutamine concentration. In conclusion, reducing glutamine concentration causes differentiation of the cell line U937 along the monocytic pathway. These effects may indicate a mechanistic basis for prior published evidence that glutaminase and glutamine antagonists are effective anti-tumor agents.

Glutamine increases collagen gene transcription in cultured human fibroblasts

We have previously shown that glutamine stimulates the synthesis of collagen in human dermal confluent fibroblast cultures (Bellon, G. et al. [1987] Biochim. Biophys. Acta, 930, 39-47). In this paper, we examine the effects of glutamine on collagen gene expression. A dose-dependent effect of glutamine on collagen synthesis was demonstrated from 0 to 0.25 mM followed by a plateau up to 10 mM glutamine. Depending on the cell population, collagen synthesis was increased by 1.3-to 2.3-fold. The mean increase in collagen and non-collagen protein synthesis was 63% and 18% respectively. Steady-state levels of alpha 1(I) and alpha 1(III) mRNAs, were measured by hybridizing total RNA to specific cDNA probes at high stringency. Glutamine increased the steady-state level of collagen alpha 1(I) and alpha 1(III) mRNAs in a dose-dependent manner. At 0.15 mM glutamine, collagen mRNAs were increased by 1.7-and 2.3-fold respectively. Nuclear run-off experiments at this concentration of glutamine indicated that the transcriptional activity was increased by 3.4-fold for the pro alpha 1(I) collagen gene. The effect of glutamine on gene transcription was also supported by the measurement of pro alpha 1(I) collagen mRNA half-life since glutamine did not affect its stability. Protein synthesis seemed to be required for the glutamine-dependent induction of collagen gene expression since cycloheximide suppressed the activation. The effect of glutamine appeared specific because analogues and/or derivatives of glutamine, such as acivicin, 6-diazo-5-oxo-L-norleucine, homoglutamine, ammonium chloride and glutamate did not replace glutamine. The influence of amino acid transport systems through plasma membrane was assessed by the use of 2(methylamino)-isobutyric acid and beta 2-aminobicyclo-(2.2.1)-heptane-2-carboxylic acid. The glutamine-dependent induction of collagen gene expression was found to be independent of transport system A but dependent on transport system L whose inhibition induced a decrease in pro alpha 1(I) collagen gene transcription by an unknown mechanism. Thus, glutamine, at physiological concentrations, indirectly regulates collagen gene expression.

Hormonal regulation of glutamine metabolism by OK cells

The precise mechanism(s) of action of PTH, insulin or glucagon in the regulation of renal glutamine and ammonia metabolism is unknown. Our aim was to delineate the effects and the site(s) of action of these hormones on renal glutamine metabolism. Experiments were carried out using OK cells as a model system. Cell cultures were incubated for three hours in a bicarbonate buffer of pH 7.4 supplemented with either 1 mM [2-15N] or [5-15N] glutamine and 10(-7) M PTH, insulin or glucagon. Comparative studies were performed at pH 6.8, 7.4 or 7.6 without hormone. PTH and acute acidosis significantly stimulated glutamine metabolism via both the phosphate-dependent glutaminase (PDG) and glutamate dehydrogenase (GLDH) pathways. The opposite was observed at pH 7.6. Insulin augmented flux via PDG with little effect on the GLDH pathway. Glucagon had insignificant effects on either PDG or GLDH pathways. Intracellular [15N] glutamate formed from [2-15N] glutamine was removed partially by transamination to alanine, aspartate and serine and partially by translocation to an extracellular compartment. Acidosis, PTH and insulin enhanced the formation of [15N] alanine with little effect on [15N] aspartate. PTH, insulin and glucagon significantly stimulated the production of [15N]serine, whereas acidosis had little effect. The translocation of intracellular glutamate was significantly increased by acidosis, PTH and insulin and decreased by acute alkalosis. The data indicate that: (a) PTH mimicks the effect of acute acidosis on renal glutamine metabolism, that is, augmented glutamine metabolism through both PDG and GLDH pathways and stimulated the output of intracellular glutamate. This effect might be mediated via decreased activity of the Na(+)-H+ exchanger associated with cellular acidification and/or through a second messenger; (b) insulin, but not glucagon, increased glutamine uptake and metabolism, and simultaneously enhanced output of intracellular glutamate sufficiently to stimulate the PDG pathway; and (c) overall, glucagon had little effect on glutamine metabolism by OK cells compared with either PTH or insulin.

Amino acid deprivation-induced stress response in the bovine renal epithelial cell line NBL-1: induction of HSP 70 by phenylalanine

Amino acid deprivation of the bovine renal epithelial cell line NBL-1 led to a range of responses by the heat shock and glucose regulated stress proteins. The classic heat shock induction of HSP 72 was found to be mimicked, without prior heat stress, by phenylalanine addition to cells simultaneously deprived of all other amino acids. Co-inclusion of alanine prevented the HSP 72 induction by phenylalanine but not that caused by heat stress. Phenylalanine also increased expression of HSP 70 mRNA in cells simultaneously deprived of other amino acids. The glucose regulated protein GRP 75 was increased upon amino acid deprivation. GRP94 was detectable in a 50 kDa form in control cells but was detected as a 94 kDa form upon amino acid deprivation which was further enhanced upon inclusion of phenylalanine. Addition of alanine to the starvation medium led to detection of the 50 kDa form only. Amino acid deprivation appears to mimic the glucose deprivation stress response. Inclusion of phenylalanine during amino acid deprivation leads to a stress response similar to that of heat shock in terms of HSP 72 induction. However, the two inducers are sensitive to different repression signals since only the phenylalanine-signal was subject to nihilation by alanine co-inclusion.

Heat shock response in the liver: expression and regulation of the hsp70 gene family and early response genes after in vivo hyperthermia

Heat shock response in cultured cells has been studied extensively; however few data are available on heat shock response in an intact organ of a living animal. In this study we analyzed the kinetics of expression of the heat shock protein 70 gene family (heat shock protein 70, heat shock cognate protein 73 and glucose-regulated protein 78) in the liver of the thermally stressed rat. New synthesis of heat shock protein 70 and heat shock cognate protein 73 was shown in liver slices pulse labeled in vitro with 35S-methionine. Accumulation of heat shock protein 70 and heat shock cognate protein 73 proteins was shown in total cellular extracts. 32P-labeled complementary DNA probes encoding heat shock protein 70, heat shock cognate protein 73 and glucose-regulated protein 78 were used to show that the levels of the corresponding messenger RNAs increase as a fraction of total RNA and in polysomes at different extents and with different kinetics. The induction of heat shock protein 70 and heat shock cognate protein 73 messenger RNAs reflected the increase in the synthesis of the corresponding proteins. Run-on transcription analysis indicated that the expression of heat shock protein 70 and heat shock cognate protein 73 genes was mainly regulated at the transcriptional level. On the contrary, both transcriptional and posttranscriptional regulatory mechanisms can explain the induction of the glucose-regulated protein 78 gene.(ABSTRACT TRUNCATED AT 250 WORDS)