Oral mucosal progenitor cells are potently immunosuppressive in a dose-independent manner

Oral mucosal lamina propria progenitor cells (OMLP-PCs) are a novel, clonally derived PC population of neural crest origin with the potential to differentiate down both mesenchymal and neuronal cell lineages. In this study we aimed to determine the immunological properties of OMLP-PCs and to establish whether they would be suitable candidates for allogeneic tissue engineering and in the treatment of immune-related diseases. OMLP-PCs demonstrated no inherent immunogenicity with insignificant expression of costimulatory molecules (CD40, CD80, CD86, CD154, and CD178) or human leukocyte antigen (HLA) class II. OMLP-PCs required 7 days of stimulation with interferon-γ (IFN-γ) to induce cell surface expression of HLA II. Mixed lymphocyte cultures and mitogen stimulation demonstrated the potent immunosuppressive capability of OMLP-PCs in a contact-independent manner. Complete inhibition of lymphocyte proliferation was seen at doses as low as 0.001% OMLP-PCs to responder lymphocytes, while annexin V staining confirmed that this immunosuppressive effect was not due to the induction of lymphocyte apoptosis. These data demonstrate, for the first time, that OMLP-PC immunomodulation, unlike that for mesenchymal stem cells, occurs via a dose- and HLA II-independent mechanism by the release of immunosuppressive soluble factors and suggests these cells may have wide ranging potential in future immune-related therapies.

A multipotent neural crest-derived progenitor cell population is resident within the oral mucosa lamina propria

Wounds within the oral mucosa, similarly to fetal wounds, exhibit rapid healing with reduced scarring. We hypothesized that a progenitor population resident within the oral mucosal lamina propria (OMLP) contributes to this preferential healing. Progenitor cells (PC) were reliably isolated from the OMLP by differential adhesion to fibronectin. Isolated colonies originating from a single cell demonstrated a rapid initial phase of proliferation, completing in excess of 50 population doublings (PDs) before entering cellular senescence. These data were supported by the expression of active telomerase within both developing colonies and expanded clones as assessed by immunocytochemistry (ICC) and the quantitative telomeric repeat amplification protocol. FACS analysis confirmed expression of the stem cell markers CD44, CD90, CD105, and CD166, but negative expression of CD34 and CD45 ruling out a hematopoietic or fibrocyte origin for these progenitors. A neural crest origin was confirmed by increased colony-forming efficiency (CFE) in the presence of Jagged 1 and the expression of a number of neural crest markers within the developing colonies by ICC and serially passaged clones by Western blotting. The multipotency of this novel PC population was demonstrated by differentiation of the cells down both mesenchymal (chondrogenic, osteoblastic, and adipogenic) and neuronal (neuron and Schwann-like cells) cell lineages. This article reports for the first time, the isolation and characterization of a novel, clonally derived PC population resident within the OMLP. The attributes of this adult stem cell (ASC) population and its accessibility lends itself to future therapeutic applications.

THE STRUCTURE AND FORMATION OF PROTEIN GRANULES IN THE FAT BODY OF AN INSECT

In the larva of the butterfly Calpodes ethlius, the fat body begins to store protein in the form of granules at about 30 to 35 hours before pupation, at a time when the endocuticle is being resorbed. At least two sorts of granule can be distinguished. The first granules to arise are those within vesicles of the Golgi complex. These may increase in size by incorporating material from microvesicles at their surface and by coalescence with one another. Later, at about 10 hours before pupation, another sort of granule arises by the isolation of regions of the endoplasmic reticulum (ER) within paired membranes derived from Golgi vesicles. Several of these ER isolation bodies coalesce, with fusion of their outer isolating membranes. The ribosomes and membranes may then disappear and the granules become indistinguishable from the protein granules formed from Golgi vesicles, or the ribosomes may remain and be embedded in dense crystalline protein, forming a storage body for both protein and RNA. Mitochondria are isolated within paired membranes in the same way as regions of the ER. The isolated mitochondria also coalesce in a similar manner. When the inner membranes are lost, the structure of a group of isolation bodies is indistinguishable from that of a cytolysome. Isolation within paired membranes, as described here, may be of general importance in segregating regions of massive lysis or massive sequestration.

An ex vivo rodent mandible culture model for bone repair

To understand fully cellular mechanisms during bone tissue repair and engineering, there is a need to develop reproducible three-dimensional organotypic culture models, whereby cells in their natural extracellular matrix can be manipulated. Limitations in current model systems do not allow for this integrated approach. This study aimed to develop and validate an ex vivo fractured rat mandible model, to investigate specific molecular and cellular processes involved in bone repair. Slices of mandible from 28-day-old male Wistar rats were cultured in Trowel-type cultures at the liquid-gas interface for up to 21 days. Maintenance of cell and tissue architecture and viability was shown within fractured mandible slices during all culture periods. Autoradiographic studies demonstrated that resident cells were actively synthesizing and secreting proteins, and cells of the osteoblast lineage were shown to survive throughout the culture periods. The model was responsive to exogenously added transforming growth factor-β1, with observed increases in cellular migration/proliferation and expression of bone matrix proteins. The ex vivo mandible model developed within this study may represent an ideal system for investigating specific processes of bone repair, as well as a promising alternative to in vivo testing of novel clinical therapeutics.

The localization of a peroxidase associated with hard cuticle formation in an insect, Calpodes ethlius stoll, Lepidoptera, Hesperiidae

The distribution of a peroxidase associated with the formation of hard cuticle has been studied in developing larvae of Calpodes ethlius. It occurs in granules in several cell types but is most easily observed in the cells making the proleg spines at the 4th to 5th molt. Light microscopy shows peroxidase in numerous granules about 0.5micro in diameter at the time the cuticle of the spine shaft is being deposited. Electron microscopy shows these granules to be multivesicular bodies with peroxidase in the matrix. Peroxidase is also found in cisternae of the rough ER near Golgi complexes, in vesicles of Golgi complexes and in the secretory vesicles which discharge to make cuticle at the apical surface. The cuticle above the plasma membrane where peroxidase is being deposited reacts with DAB in the absence of hydrogen peroxide. Presumably this cuticle has been 'peroxidized' as a first stage in stabilization by cross-linking. Some of the peroxidase secreted at the apical surface is pinocytosed and transported to the multivesicular bodies, suggesting that there may be a precise control of the cuticular environment through the turnover of its soluble components.

TRIM32 is an E3 ubiquitin ligase for dysbindin

Mutations in the gene encoding tripartite motif protein 32 (TRIM32) cause two seemingly diverse diseases: limb-girdle muscular dystrophy type 2H (LGMD2H) or sarcotubular myopathy (STM) and Bardet–Biedl syndrome type 11(BBS11). Although TRIM32 is involved in protein ubiquitination, its substrates and the molecular consequences of disease-causing mutations are poorly understood. In this paper, we show that TRIM32 is a widely expressed ubiquitin ligase that is localized to the Z-line in skeletal muscle. Using the yeast two-hybrid system, we found that TRIM32 binds and ubiquitinates dysbindin, a protein implicated in the genetic aetiology of schizophrenia, augmenting its degradation. Small-interfering RNA-mediated knock-down of TRIM32 in myoblasts resulted in elevated levels of dysbindin. Importantly, the LGMD2H/STM-associated TRIM32 mutations, D487N and R394H impair ubiquitin ligase activity towards dysbindin and were mislocalized in heterologous cells. These mutants were able to self-associate and also co-immunoprecipitated with wild-type TRIM32 in transfected cells. Furthermore, the D487N mutant could bind to both dysbindin and its E2 enzyme but was defective in monoubiquitination. In contrast, the BBS11 mutant P130S did not show any biochemical differences compared with the wild-type protein. Our data identify TRIM32 as a regulator of dysbindin and demonstrate that the LGMD2H/STM mutations may impair substrate ubiquitination.

The neurobiology of the dystrophin-associated glycoprotein complex

While the function of dystrophin in muscle disease has been thoroughly investigated, dystrophin and associated proteins also have important roles in the central nervous system. Many patients with Duchenne and Becker muscular dystrophies (D/BMD) have cognitive impairment, learning disability, and an increased incidence of some neuropsychiatric disorders. Accordingly, dystrophin and members of the dystrophin-associated glycoprotein complex (DGC) are found in the brain where they participate in macromolecular assemblies that anchor receptors to specialized sites within the membrane. In neurons, dystrophin and the DGC participate in the postsynaptic clustering and stabilization of some inhibitory GABAergic synapses. During development, alpha-dystroglycan functions as an extracellular matrix receptor controlling, amongst other things, neuronal migration in the developing cortex and cerebellum. Several types of congenital muscular dystrophy caused by impaired alpha-dystroglycan glycosylation cause neuronal migration abnormalities and mental retardation. In glial cells, the DGC is involved in the organization of protein complexes that target water-channels to the plasma membrane. Finally, mutations in the gene encoding epsilon-sarcoglycan cause the neurogenic movement disorder, myoclonus-dystonia syndrome implicating epsilon-sarcoglycan in dopaminergic neurotransmission. In this review we describe the recent progress in defining the role of the DGC and associated proteins in the brain.

Heat shock protein accumulation and heat shock transcription factor activation in rat skeletal muscle during compensatory hypertrophy

AIM

To assess the stress/heat shock protein (HSP) and heat shock factor activation response in overloaded (hypertrophied) plantaris muscles.

METHODS

Male Sprague-Dawley rats (n = 5 per time point) underwent unilateral removal of the left gastrocnemius muscle. After 1, 2, 3, 5, 7, 14 and 28 days, plantaris muscles were removed, weighted rapidly frozen in liquid nitrogen. Total protein content was determined and HSP 25 and HSP 72 contents were assessed by Western blotting. Heat shock transcription factor (HSF) activation was assessed by electrophoretic mobility shift assay (EMSA).

RESULTS

While plantaris muscle mass was significantly increased 3 days after the imposition of overload and remained elevated thereafter confirming muscle hypertrophy, muscle protein content was not increased until 7 days after the imposition of overload. HSP 72 content was significantly increased at 3 days, while HSP 25 content was not significantly increased until 7 days after synergistic muscle removal. HSF activation was detected at 1, 2 and 3 days of overload but undetectable thereafter. The addition of HSF1- and HSF2-specific antibodies to extracts prior to EMSA failed to supershift the HSF-heat shock element complex.

CONCLUSION

The temporal pattern of both HSF activation and HSP expression in skeletal muscle undergoing hypertrophy suggests the increased level of the observed HSPs may be both a consequence of both the immediate stress of overload and the hypertrophic process. The inability of HSF1- and HSF2-specific antibodies to cause supershifts suggests the HSF detected during overload may not be HSF1 or HSF2.

Comparison of broiler performance when fed diets containing event DP-356Ø43-5 (Optimum GAT), nontransgenic near-isoline control, or commercial reference soybean meal, hulls, and oil

Event DP-356Ø43-5 (356043; Optimum GAT) is a genetically modified soybean (Glycine max) that was produced by insertion of the gat4601 and gm-hra genes. The expression products of these genes are the glyphosate acetyltransferase 4601 and acetolactate synthase proteins, respectively. Expression of the glyphosate acetyltransferase 4601 protein confers tolerance in planta to the herbicidal active ingredient glyphosate, whereas expression of the acetolactate synthase protein confers tolerance to sulfonylurea and imidazolinone herbicides. The objective of this study was to compare the nutritional equivalence of 356043 soybeans to nontransgenic soybeans in a 42-d feeding trial in broiler chickens. Diets were prepared using processed fractions (meal, hulls, and oil) from untreated 356043 soybean plants or from soybean plants treated with a mixture of glyphosate, chlorimuron, and thifensulfuron (356043 + Gly/SU). For comparison, additional diets were produced with soybean fractions obtained from a nontransgenic near-isoline (control; 091) and nontransgenic commercial Pioneer varieties (93B86, 93B15, and 93M40). Diets were fed to Ross x Cobb broilers (n = 120/group, 50% male and 50% female) in 3 phases. Starter diets contained 30% soybean meal, grower diets 26% soybean meal, and finisher diets 21.5% soybean meal. Soybean hulls and oil were added at 1.0 and 0.5%, respectively, across all diets in each phase. No statistically significant differences were observed in mortality, growth performance variables, or carcass and organ yields between broilers consuming diets produced with 356043 or 356043 + Gly/SU soybean fractions and those consuming diets produced with near-isoline control soybean fractions. Additionally, all performance and carcass variables from control, 356043, and 356043 + Gly/SU soybean treatment groups fell within the tolerance intervals constructed using data from reference soybean groups. Based on the results from this study, it was concluded that 356043 soybean was nutritionally equivalent to nontransgenic control soybean with a comparable genetic background.

SGCE missense mutations that cause myoclonus-dystonia syndrome impair ε-sarcoglycan trafficking to the plasma membrane: modulation by ubiquitination and torsinA

Myoclonus-dystonia syndrome (MDS) is a genetically heterogeneous disorder characterized by myoclonic jerks often seen in combination with dystonia and psychiatric co-morbidities and epilepsy. Mutations in the gene encoding epsilon-sarcoglycan (SGCE) have been found in some patients with MDS. SGCE is a maternally imprinted gene with the disease being inherited in an autosomal dominant pattern with reduced penetrance upon maternal transmission. In the central nervous system, epsilon-sarcoglycan is widely expressed in neurons of the cerebral cortex, basal ganglia, hippocampus, cerebellum and the olfactory bulb. epsilon-Sarcoglycan is located at the plasma membrane in neurons, muscle and transfected cells. To determine the effect of MDS-associated mutations on the function of epsilon-sarcoglycan we examined the biosynthesis and trafficking of wild-type and mutant proteins in cultured cells. In contrast to the wild-type protein, disease-associated epsilon-sarcoglycan missense mutations (H36P, H36R and L172R) produce proteins that are undetectable at the cell surface and are retained intracellularly. These mutant proteins become polyubiquitinated and are rapidly degraded by the proteasome. Furthermore, torsinA, that is mutated in DYT1 dystonia, a rare type of primary dystonia, binds to and promotes the degradation of epsilon-sarcoglycan mutants when both proteins are co-expressed. These data demonstrate that some MDS-associated mutations in SGCE impair trafficking of the mutant protein to the plasma membrane and suggest a role for torsinA and the ubiquitin proteasome system in the recognition and processing of misfolded epsilon-sarcoglycan.

Structural stability and chromosome-specific telomere length is governed by cis-acting determinants in humans

Single telomere length analysis (STELA) of the XpYp telomere has revealed extensive allelic variation and ultra-short telomeres in senescent cells. Superimposed on end-replication losses are additional mutational events that result in large-scale changes in telomere length. In order to establish if the dynamics of the XpYp telomere are typical of human telomeres, here we describe an analysis using STELA of the telomeres of 2p, 11q, 12q, 17p and XpYp. The dynamics of telomere loss (erosion rates and stochastic length changes) was conserved among 2p, 11q, 12q and XpYp within the same cell strains and was dependent on the replicative kinetics of the cells in culture. However, of the telomeres analysed, the telomere of 17p was more stable with a striking paucity of large-scale length changes, and exhibited the shortest recorded allelic distribution (300 bp) in senescent cells and displayed a general, but not absolute, trend towards being the shortest telomere. Ectopic over-expression of hTERT homogenized both allelic and chromosome-specific telomeric distributions. However, telomerase-expressing cancer cells displayed both allelic variation and chromosome-specific telomere length, with 17p displaying the shortest allelic telomere length. Although other telomeres in the genome may share the properties of 17p, these data suggest that physiological levels of telomerase allow differential telomere length regulation and indicate the presence of cis-acting factors that govern both telomeric stability and chromosome-specific telomere length in the presence of telomerase.

Retention of intrinsic stem cell hierarchies in carcinoma-derived cell lines

Recent work indicates that the growth and behavior of cancers are ultimately determined by a small subpopulation of malignant stem cells and that information about the properties of these cells is urgently needed to enable their targeting for therapeutic elimination. A key feature of normal stem cells is their asymmetrical division, the mechanism that allows stem cell self-renewal while producing hierarchies of amplifying and differentiating cells that form the bulk of the tissue. Most cancer deaths result from epithelial malignancies, but the extent to which the hierarchical proliferative stem and amplifying cell patterns of normal epithelia are actually retained in epithelial malignancies has been unclear. Here we show that even cell lines generated from carcinomas consistently produce in vitro colony patterns unexpectedly similar to those produced by the stem and amplifying cells of normal epithelia. From the differing types of colony morphologies formed, it is possible to predict both the growth potential of their constituent cells and their patterns of macromolecular expression. Maintenance of a subpopulation of stem cells during passage of cell lines indicates that the key stem cell property of asymmetrical division persists but is shifted towards enhanced stem cell self-renewal. The presence of malignant epithelial stem cells in vivo has been shown by serial transplantation of primary cancer cells and the present observations indicate that stem cell patterns are robust and persist even in cell lines. An understanding of this behavior should facilitate studies directed towards the molecular or pharmacologic manipulation of malignant stem cell survival.

Interactions of 12-lipoxygenase with phospholipase A2 isoforms following platelet activation through the glycoprotein VI collagen receptor

Recent studies implicate the collagen receptor, glycoprotein VI (GPVI) in activation of platelet 12-lipoxygenase (p12-LOX). Herein, we show that GPVI-stimulated 12-hydro(peroxy)eicosatetraenoic acid (H(P)ETE) synthesis is inhibited by palmityl trifluromethyl ketone or oleyloxyethylphosphocholine , but not bromoenol lactone, implicating secretory and cytosolic, but not calcium-independent phospholipase A2 (PLA2) isoforms. Also, following GPVI activation, 12-LOX co-immunoprecipitates with both cytosolic and secretory PLA2 (sPLA2). Finally, venoms containing sPLA2 acutely activate p12-LOX in a dose-dependent manner. This study shows that platelet 12-H(P)ETE generation utilizes arachidonate substrate from both c- and sPLA2 and that 12-LOX functionally associates with both PLA2 isoforms.

Intrinsic Patterns of Behavior of Epithelial Stem Cells

The early concepts concerning hematopoietic and epithelial stem cells that were derived from kinetic studies have been greatly enhanced by new information about a range of other properties of somatic and embryonic stem cells. Firstly, the stem and amplifying pattern characteristically established by epithelial lineages has been found to represent an intrinsic pattern that is generated by somatic epithelial stem cells without the need for additional environmental information. Secondly, it is now apparent that somatic epithelial stem cells are plastic and can be directed into a range of new pathways of differentiation by heterotypic interactions. The mechanisms of this plasticity need to be reconciled with the normally stable commitment of these cells to production only of progeny entering a tightly restricted range of phenotypic pathways. The present review discusses the intrinsic properties of epithelial stem cells and how they may be acted upon by connective tissues to generate a wide range of phenotypically different epithelial structures.

Construction of large area organotypical cultures of oral mucosa and skin

BACKGROUND

Skin and oral mucosal keratinocytes grown in vitro usually lose their normal patterns of differentiation, unless grown as organotypical cultures that are constructed by allowing collagen gels containing fibroblasts to contract before they are plated with keratinocytes and raised to the air/medium interface. However, the contraction process tends to produce small irregular cultures.

METHODS

To generate uniformly differentiating large cultures, we have investigated several aspects of the factors involved in the culture construction. By adjusting the number of fibroblasts used and by plating the matrices with keratinocytes prior to contraction, cultures of up to 72 cm2 were constructed.

RESULTS

The cultures retained almost the full surface areas of the original matrices and showed uniform patterns of epithelial plating and differentiation. Immunostaining for cytokeratins and integrins indicated restoration of in vitro phenotypes similar to those of the epithelial tissues of origin.

CONCLUSIONS

These methods successfully generate cultures required for certain types of investigations and tissues that are suitable for clinical use as grafts.

Keratinocyte growth factor and scatter factor expression by regionally defined oral fibroblasts

Keratinocyte growth factor (KGF) and hepatocyte growth factor/scatter factor (SF) are two signalling molecules thought to play important roles in regulating epithelial-mesenchymal interactions. Expression of both factors by fibroblasts in subepithelial connective tissue may play a role in maintaining epithelial integrity in health and in the apical migration of junctional epithelium in periodontitis. The aims of this study were (a) to compare expression levels of KGF and SF by periodontal ligament (PDL) and gingival fibroblasts; and (ii) to determine the effects of interleukin (IL)-1 beta, transforming growth factor (TGF)-beta 1, platelet-derived growth factor (PDGF)-BB and epidermal growth factor (EGF) on KGF/SF expression by these cell populations. Three paired PDL and gingival fibroblast strains were developed. The KGF and SF protein levels were analysed by enzyme-linked immunosorbent assay. Relative levels of KGF and SF mRNA in cytokine-treated cultures were determined using semiquantitative reverse transcriptase polymerase chain reaction. No differences in the levels of KGF and SF produced by PDL and gingival (SOG) populations were found. In both cell types IL-1 beta stimulated KGF and SF expression, while TGF-beta 1 significantly inhibited expression at both the mRNA and protein levels. Epidermal growth factor and PDGF-BB induced differing effects on expression, stimulating SF protein production but inhibiting KGF output in both fibroblast populations. Differences in response to EGF and PDGF were also seen between paired PDL and gingival fibroblasts.

Continuous and pulsed ultrasound do not increase heat shock protein 72 content

Therapeutic ultrasound (US) is a common treatment used in the rehabilitation of injured muscle. To determine whether therapeutic US could increase the content of heat shock protein (HSP) 72 in skeletal muscle, male Sprague-Dawley rats were anesthetized and the muscles from one hind limb treated with 15 min of US at 1 MHz using either: 1. continuous US at 1.0 W/cm(2), 2. pulsed US at 2.0 W/cm(2) at 50% duty cycle, or 3. pulsed US at 1.0 W/cm(2) at 20% duty cycle. All treatments were applied using a transducer (1.6-cm diameter) on an area of the rat hind limb twice the size of the sound head. At 24 h following treatment, the plantaris, soleus, white and red gastrocnemius muscles were removed and assessed for HSP 72 content by Western blotting. No significant increases in HSP 72 content were detected in any of the muscles examined following any US treatment. These results suggest muscle HSP content is not elevated following a typical therapeutic dose of either continuous or pulsed US in the rat.

Cold stress does not induce stress proteins SP 25 and SP 72 in rat skeletal muscle

Cryotherapy is a common treatment for musculoskeletal injuries, yet the mechanism(s) underlying its effects remain unclear. Since cryotherapeutic treatment often involves temperatures that are known to induce the protective stress proteins (SPs), we determined whether SP 25 and SP 72 expression was altered following a 20-min cold stress to the hindlimb muscles of Sprague-Dawley rats. The right hindlimb of anesthetized animals was placed in an ice bath until muscle temperature decreased to either 8.4 +/- 0.4 degrees C or 19.7 +/- 0.3 degrees C for 20 min. After a 24-h recovery, the white and red gastrocnemius, plantaris, soleus, extensor digitorum longus, and tibialis anterior muscles from both legs were removed and rapidly frozen in liquid nitrogen. Portions of the muscles were homogenized and SP 25 and SP 72 content was assessed by SDS-PAGE/Western blot analyses. Quantification of SP 25 and SP 72 by densitometric scanning of blots demonstrated no significant increases in SP 25 or SP 72 content in any of the muscles exposed to either the 8 or the 20 degrees C cold stress compared to muscles from the unstressed contralateral limbs. These results suggest that a 20-min cold stress of 8 degrees C or 20 degrees C does not increase muscle SP 25 or SP 72 content.

The myocardial heat shock response following sodium salicylate treatment

In cultured cells, salicylate has been shown to potentiate the induction of Hsp72 so that a mild heat stress (40 degrees C) in the presence of salicylate induces an Hsp72 response that is similar to a severe heat stress (42 degrees C). To determine whether salicylate can potentiate the myocardial Hsp70 response in vivo and confer protection from an ischemic stress, male Sprague-Dawley rats (250-300 g) were placed into 5 groups: (1) control, (2) salicylate only (400 mg/kg), (3) mild heat stress (40 degrees C for 15 minutes), (4) mild heat stress plus salicylate, and (5) severe heat stress (42 degrees C for 15 minutes). Twenty-four hours following salicylate treatment and/or heat stress, animals were anesthetized, their hearts rapidly isolated, and hemodynamic function evaluated using the Langendorff technique. Hsp72 content was subsequently assessed by Western blotting. Although salicylate in combination with a mild heat stress induced heat shock factor activation, only the hearts from severely heat-stressed animals (42 degrees C) demonstrated a significantly elevated myocardial Hsp72 content and a significantly enhanced postischemic recovery of left ventricular developed pressure and rates of contraction and relaxation. These results support the role for Hsp72 as a protective protein and suggest that neither salicylate treatment alone nor salicylate in combination with a mild heat stress potentiates the myocardial Hsp72 response.

The myocardial heat shock response following sodium salicylate treatment

In cultured cells, salicylate has been shown to potentiate the induction of Hsp72 so that a mild heat stress (40 degrees C) in the presence of salicylate induces an Hsp72 response that is similar to a severe heat stress (42 degrees C). To determine whether salicylate can potentiate the myocardial Hsp70 response in vivo and confer protection from an ischemic stress, male Sprague-Dawley rats (250-300 g) were placed into 5 groups: (1) control, (2) salicylate only (400 mg/kg), (3) mild heat stress (40 degrees C for 15 minutes), (4) mild heat stress plus salicylate, and (5) severe heat stress (42 degrees C for 15 minutes). Twenty-four hours following salicylate treatment and/or heat stress, animals were anesthetized, their hearts rapidly isolated, and hemodynamic function evaluated using the Langendorff technique. Hsp72 content was subsequently assessed by Western blotting. Although salicylate in combination with a mild heat stress induced heat shock factor activation, only the hearts from severely heat-stressed animals (42 degrees C) demonstrated a significantly elevated myocardial Hsp72 content and a significantly enhanced postischemic recovery of left ventricular developed pressure and rates of contraction and relaxation. These results support the role for Hsp72 as a protective protein and suggest that neither salicylate treatment alone nor salicylate in combination with a mild heat stress potentiates the myocardial Hsp72 response.