Prostaglandins stimulate the stress-induced synthesis of hsp27 and alpha B crystallin

The heat shock protein response following eccentric exercise in human skeletal muscle is unaffected by local NSAID infusion

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely consumed in relation to pain and injuries in skeletal muscle, but may adversely affect muscle adaptation probably via inhibition of prostaglandin synthesis. Induction of heat shock proteins (HSP) represents an important adaptive response in muscle subjected to stress, and in several cell types including cardiac myocytes prostaglandins are important in induction of the HSP response. This study aimed to determine the influence of NSAIDs on the HSP response to eccentric exercise in human skeletal muscle. Healthy males performed 200 maximal eccentric contractions with each leg with intramuscular infusion of the NSAID indomethacin or placebo. Biopsies were obtained from m. vastus lateralis before and after (5, 28 hrs and 8 days) the exercise bout from both legs (NSAID vs unblocked leg) and analysed for expression of the HSPs HSP70, HSP27 and αB-crystallin (mRNA and protein). NSAID did not affect the mRNA expression of any of the HSPs. Compared to pre values, the mRNA expression of all HSPs was increased; αB-crystallin, 3.6- and 5.4-fold; HSP70, 26- and 3.4-fold; and HSP27: 4.8- and 6.5-fold at 5 and 28 hrs post-exercise, respectively (all p < 0.008). Immunohistochemical stainings for αB-crystallin and HSP70 revealed increased staining in some samples but with no differences between legs. Changes in force-generating capacity correlated with both αB-crystallin and HSP70 mRNA and immunohistochemisty data. Increased expression of HSPs was observed on mRNA and protein level following eccentric exercise; however, this response was unaffected by local intramuscular infusion of NSAIDs.

The protective and therapeutic function of small heat shock proteins in neurological diseases

Historically, small heat shock proteins (sHSPs) have been extensively studied in the context of being intracellular molecular chaperones. However, recent studies looking at the role of sHSPs in neurological diseases have demonstrated a near universal upregulation of certain sHSPs in damaged and diseased brains. Initially, it was thought that sHSPs are pathological in these disease states because they are found in the areas of damage. However, transgenic overexpression and exogenous administration of sHSPs in various experimental disease paradigms have shown just the contrary – that sHSPs are protective, not pathological. This review examines sHSPs in neurological diseases and highlights the potential for using these neuroprotective sHSPs as novel therapeutics. It first addresses the endogenous expression of sHSPs in a variety of neurological disorders. Although many studies have examined the expression of sHSPs in neurological diseases, there are no review articles summarizing these data. Furthermore, it focuses on recent studies that have investigated the therapeutic potential of sHSPs for neurological diseases. Finally, it will explain what we think is the function of endogenous sHSPs in neurological diseases.

Exercise can increase small heat shock proteins (sHSP) and pre- and post-synaptic proteins in the hippocampus

The molecular events mediating the complex interaction between exercise and cognition are not well-understood. Although many aspects of the signal transduction pathways mediate exercise induced improvement in cognition are elucidated, little is known about the molecular events interrelating physiological stress with synaptic proteins, following physical exercise. Small heat shock proteins (sHSP), HSP27 and alpha-B-crystallin are co-localized to synapses and astrocytes, but their role in the brain is not well-understood. We investigated whether their levels in the hippocampus were modulated by exercise, using a well characterized voluntary exercise paradigm. Since sHSP are known to be regulated by many intracellular signaling molecules in other cells types outside the brain, we investigated whether similar regulation may serve a role in the brain by measuring protein kinase B (PKB/Akt), pGSK3 and the mitogen activated protein (MAP) kinases, p38, phospho-extracellular signal-regulated kinase (pERK) and phospho-c-Jun kinase (pJNK). Results demonstrated exercise-dependent increases in HSP27 and alpha-B-crystallin levels. We observed that increases in sHSP coincided with robust elevations in the presynaptic protein, SNAP25 and the post-synaptic proteins NR2b and PSD95. Exercise had a differential impact on kinases, significantly reducing pAkt and pERK, while increasing p38 MAPK. In conclusion, we demonstrate four early novel hippocampal responses to exercise that have not been identified previously: the induction of (1) sHSPs (2) the synaptic proteins SNAP-25, NR2b, and PSD-95, (3) the MAP kinase p38 and (4) the immediate early gene product MKP1. We speculate that sHSP may play a role in synaptic plasticity in response to exercise.

Alpha2 adrenoreceptor agonist regulates protein kinase C-induced heat shock protein 27 phosphorylation in C6 glioma cells

Dexmedetomidine (Dexmd), a potent and highly specific alpha(2) adrenoreceptor agonist, is an efficient therapeutic agent for sedation. Dexmd has been recently reported to have a neuroprotective effect. Heat shock protein (HSP) 27, a low-molecular weight HSP has been shown to be expressed following cerebral ischemia in astrocytes but not in neurons. HSP27 expression is involved in ischemic tolerance of the brain. This study investigated the effect of Dexmd on HSP27 in rat C6 glioma cells. 12-O-tetradecanoylphorbol-13-actate (TPA), a direct activator of protein kinase C (PKC), stimulated the phosphorylation of HSP27 at Ser82, but not Ser15 in a time-dependent manner. Prostaglandin (PG) E(1) or PGE(2) which activates the adenylyl cyclase-cAMP system as well as forskolin and dibutyryl-cAMP, suppressed the TPA-induced phosphorylation of HSP27. Dexmd reversed the suppression of HSP27 phosphorylation by the adenylyl cyclase-cAMP system. Therefore, these results strongly suggest that Dexmd reverses the suppression of HSP27 phosphorylation by the adenylyl cyclase-cAMP system activation through the inhibition of its system in C6 cells. alpha(2) Adrenoreceptor agonists may therefore show a neuroprotective effect through the modification of HSP27 phosphorylation induced by PKC activation.

Study of protein targets for covalent modification by the antitumoral and anti-inflammatory prostaglandin PGA1: focus on vimentin

Prostaglandins with cyclopentenone structure (cyPG) display potent antiproliferative actions that have elicited their study as potential anticancer agents. Several natural and synthetic analogs of the cyPG prostaglandin A(1) (PGA(1)) have proven antitumoral efficacy in cancer cell lines and animal models. In addition, PGA(1) has been used as an inhibitor of transcription factor NF-kappaB-mediated processes, including inflammatory gene expression and viral replication. An important determinant for these effects is the ability of cyPG to form Michael adducts with free thiol groups. The chemical nature of this interaction implies that PGA(1) could covalently modify cysteine residues in a large number of cellular proteins potentially involved in its beneficial effects. However, only a few targets of PGA(1) have been identified. In previous work, we have observed that a biotinylated analog of PGA(1) that retains the cyclopentenone moiety (PGA(1)-B) binds to multiple targets in fibroblasts. Here, we have addressed the identification of these targets through a proteomic approach. Cell fractionation followed by avidin affinity chromatography yielded a fraction enriched in proteins modified by PGA(1)-B. Analysis of this fraction by SDS-PAGE and LC-MS/MS allowed the identification of the chaperone Hsp90, elongation and initiation factors for protein synthesis and cytoskeletal proteins including actin, tubulin and vimentin. Furthermore, we have characterized the modification of vimentin both in vitro and in intact cells. Our observations indicate that cysteine 328 is the main site for PGA(1) addition. These results may contribute to a better understanding of the mechanism of action of PGA(1) and the potential of cyPG-based therapeutic strategies.

Heat shock protein 27: its potential role in vascular disease

Heat shock proteins are molecular chaperones that have an ability to protect proteins from damage induced by environmental factors such as free radicals, heat, ischaemia and toxins, allowing denatured proteins to adopt their native configuration. Heat shock protein-27 (Hsp27) is a member of the small Hsp (sHsp) family of proteins, and has a molecular weight of approximately 27 KDa. In addition to its role as a chaperone, it has also been reported to have many additional functions. These include effects on the apoptotic pathway, cell movement and embryogenesis. In this review, we have focused on its possible role in vascular disease.

Activation of the Nrf2/antioxidant response pathway increases IL-8 expression

Oxidant stress can initiate or enhance inflammatory responses during tissue injury, possibly through activation of redox-sensitive chemokines. Because the transcription factor Nrf2 (NF-E2-related factor 2) is responsive to oxidative stress, and induces expression of cytoprotective and antioxidant genes that attenuate tissue injury, we postulated that Nrf2 may also regulate chemokine expression. To test this hypothesis, Nrf2 expression was directly increased in primary human kidney mesangial cells and aortic endothelial cells, or cell lines with an adenoviral construct, and the effects on the pro-inflammatory chemokine interleukin-8 (IL-8) were assessed. Nrf2 expression significantly increased IL-8 mRNA levels and protein secretion. Nrf2 caused only a weak induction of IL-8 transcription, but significantly increased the half-life of IL-8 mRNA. These data demonstrate that activation of the Nrf2/antioxidant response pathway induces expression of IL-8. The dominant mechanism of Nrf2-mediated IL-8 induction is through mRNA stabilization. Considering the evidence that Nrf2 activation is mainly cytoprotective, these observations raise the possibility that under certain circumstances IL-8 may serve an anti-inflammatory role and thereby contribute to the resolution of tissue injury.

Grp78 is essential for 11-deoxy-16,16-dimethyl PGE2-mediated cytoprotection in renal epithelial cells

11-Deoxy-16,16-dimethyl PGE2(DDM-PGE2) protects renal proximal tubule epithelial cells (LLC-PK1) against the toxicity induced by 2,3,5- tris(glutathion- S-yl)hydroquinone (TGHQ), a potent nephrotoxic and nephrocarcinogenic metabolite of hydroquinone. We have now determined the ability of DDM-PGE2to protect against other renal toxicants and report that DDM-PGE2only protects against oncotic cell death, induced by H2O2, iodoacetamide, and TGHQ, but not against apoptotic cell death induced by cisplatin, mercuric chloride, or tumor necrosis factor-α. DDM-PGE2-mediated cytoprotection is associated with the upregulation of at least five proteins, including the major endoplasmic reticulum (ER) chaperone glucose-regulated protein 78 (Grp78). To elucidate the role of Grp78 in oncotic cell death, we used LLC-PK1cells in which induction of grp78 expression was disrupted by stable expression of an antisense grp78 RNA (pkASgrp78). As anticipated, DDM-PGE2failed to induce Grp78 in pkASgrp78 cells, with a concomitant inability to provide cytoprotection. In contrast, DDM-PGE2induced Grp78 and afforded cytoprotection against H2O2, iodoacetamide, and TGHQ in empty vector transfected cells (pkNEO). These data suggest that Grp78 plays an essential role in DDM-PGE2-mediated cytoprotection. Moreover, TGHQ-induced p38 MAPK activation is disrupted under conditions of a compromised ER stress response in pkASgrp78 cells, which likely contributes to the loss of cytoprotection. Finally, using two-dimensional gel electrophoresis coupled to matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy, we found that DDM-PGE2induced several proteins in pkNEO cells, but not in pkASgrp78 cells, including retinol-binding protein, myosin light chain, and heat shock protein 27. The findings suggest that additional proteins may act in concert with Grp78 during DDM-PGE2-mediated cytoprotection against oncotic cell death.

Stress protein activation by the cyclopentenone prostaglandin 15-deoxy-Δ12,14-prostaglandin J2 in human mesangial cells

BACKGROUND

The cyclopentenone prostaglandin 15-deoxy-delta12,14-prostaglandin J2 (15dPGJ2) affects mesangial proliferation, survival and production of proinflammatory proteins. During a survey of the mesangial cell proteome after treatment with 15dPGJ2, heat shock protein 70 (HSP70) was found to be the most conspicuously up-regulated protein, suggesting that stress proteins are key mediators or modulators of the effects of 15dPGJ2. Because cyclopentenone prostaglandins are highly reactive toward intracellular thiols, the role of intracellular thiol modification in the stress response to 15dPGJ2 was examined.

METHODS

Human mesangial cells were treated with 15dPGJ2 and intracellular thiol status was monitored by the fluorescent thiol probe monobromobimane (MBB). Specific intracellular thiol pools were manipulated by treating the cells with buthionine sulfoximine (BSO) to deplete glutathione (GSH), or phenylarsine oxide (PAO) to modify protein vicinal dithiols. Transcription pathways were examined with reporter gene or adenoviral constructs.

RESULTS

15dPGJ2 decreased mesangial GSH and other intracellular thiols, but depletion of GSH specifically with BSO did not induce HSP70. Thiol-replenishing reagents, which can restore modified protein thiols, attenuated 15dPGJ2-induced HSP70 levels. Furthermore, PAO mimicked the effects of 15dPGJ2 on HSP70. 15dPGJ2 also activated the stress-responsive transcription factor Nrf2, which requires thiol modification of its cytoplasmic inhibitor protein for transcriptional activity, and induced the Nrf2-dependent stress protein heme oxygenase-1 (HO-1).

CONCLUSION

15dPGJ2 activates a stress response in human mesangial cells by covalent modification of protein thiols through its unique cyclopentenone ring structure. This stress response may be beneficial in preventing renal cell injury or death during kidney inflammation or ischemia.

15-Deoxy-Delta(12,14)-prostaglandin J(2) facilitates thyroglobulin production by cultured human thyrocytes

A cyclopentenone-type prostaglandin, 15-deoxy-Delta(12, 14)-prostaglandin J(2) (15-d-PGJ(2)), has been shown to induce the cellular stress response and to be a ligand for the peroxisome proliferator-activated receptor (PPAR)-gamma. We studied its effect on the basal and thyrotropin (TSH)-induced production of thyroglobulin (TG) by human thyrocytes cultured in the presence of 10% FBS. In 15-d-PGJ(2)-treated cells in which the agent itself did not stimulate cAMP production, both the basal production of TG and the response to TSH were facilitated, including the production of TG and cAMP, whereas such production was decreased in untreated cells according to duration of culture. PGD(2) and PGJ(2), which are precursors to 15-d-PGJ(2), exhibited an effect similar to 15-d-PGJ(2). However, the antidiabetic thiazolidinediones known to be specific ligands for PPAR-gamma, and WY-14643, a specific PPAR-alpha ligand, lacked this effect. 15-d-PGJ(2) and its precursors, but not the thiazolidinediones, induced gene expression for heme oxygenase-1 (HO-1), a stress-related protein, and strongly inhibited interleukin-1 (IL-1)-induced nitric oxide (NO) production. Cyclopentenone-type PGs have been recently shown to inhibit nuclear factor-kappaB (NF-kappaB) activation via a direct and PPAR-independent inhibition of inhibitor-kappaB kinase, suggesting that, in human thyrocytes, such PGs may inhibit IL-1-induced NO production, possibly via an inhibition of NF-kappaB activation. On the other hand, sodium arsenite, a known activator of the stress response pathway, induced HO-1 mRNA expression but lacked a promoting effect on TG production. Thus 15-d-PGJ(2) and its precursors appear to facilitate TG production via a PPAR-independent mechanism and through a different pathway from the cellular stress response that is available to cyclopentenone-type PGs. Our findings reveal a novel role of these PGs associated with thyrocyte differentiation.

Induction of Hsp68 by oxidative stress involves the lipoxygenase pathway in C6 rat glioma cells

The induction of Hsp68 by heat shock (HS) and oxidative stress (OS) involves different pathways in C6 rat glioma cells. The pathways were analyzed by specific inhibitors of signal transduction cascades. Quercetin (inhibitor of PLA(2) and lipoxygenase) inhibited only the OS-induced but not the HS-induced expression of Hsp68. Preincubation with quinacrine (inhibitor of PLA(2)) before stress also suppressed the expression of Hsp68 only after oxidative stress. Moreover, another inhibitor of lipoxygenase (alpha-tocopherol) exclusively suppressed OS-induced Hsp68 expression. This different regulation was confirmed by exposing the cells to arachidonic acid (AA) during stress which strongly increased the induction of Hsp68 only after OS. PGE(2) (metabolite of cyclooxygenase) and indomethacin (inhibitor of cyclooxygenase) had no influence on Hsp68 expression in response to both stressors. The results suggest that the induction of Hsp68 by oxidative stress is mainly transmitted by the lipoxygenase pathway in C6 rat glioma cells.

Review: Age-related cataract: immunity and lens epithelium-derived growth factor (LEDGF)

This short review summarizes our recent work and relevant publications on autoimmunity and cataract. A complete review of this subject is beyond the scope of this paper. Age-related cataract (ARC) is the leading cause of world blindness. In spite of more than fifty years of basic and clinical research, there is no nonsurgical intervention to prevent or treat ARC, but there is a better understanding of the manifold complexities of this age-related condition. ARC is a multifactorial condition in which incidence and progress are modified by factors such as age, sex, radiation [visible, ultraviolet (UV), and X-ray], oxidation, physical trauma, diet, and medications. The lens contains at least three different cell types: central epithelial cells, dividing germinative epithelial cells, and fiber cells. The central epithelial cells covering the anterior axial part of the lens do not divide but survive throughout life. The bulk of the lens comprises anucleate fiber cells, differentiated germinative epithelial cells, which have undergone an apoptosis-like change "diffoptosis" to become elongated, crystallin-rich, organelle-deficient, cells. The epithelial cells and their active transport mechanisms maintain lens homeostasis and clarity. The survival mechanisms of the central lens epithelial cells (LECs) are unknown. In other cells, growth or survival factors, when present, enhance survival and, when absent or deficient, induce programmed cell death "apoptosis". Many developing mammalian cells produce signal proteins, or require signal proteins from other cells, to avoid apoptosis. Although much is known about the role of growth factors in the lens, less is known about how such signals are involved in the survival and death of LECs. We have hypothesized that LECs, like other mammalian cells, use signal proteins to regulate growth, survival, and apoptosis, and we have begun a search for such molecules. Furthermore, we have hypothesized that such factors, if found, may also be involved in the death of LECs, the consequent alteration of lens homeostasis and, eventually, certain types of ARC.