Poly(ADP-ribose) polymerase-1 inhibition increases expression of heat shock proteins and attenuates heat stroke-induced liver injury

Clonorchis sinensis aggravated liver fibrosis by activating PARP-1 signaling to induce parthanatos via DNA damage

Clonorchis sinensis is an important food-borne zoonotic parasite that is highly associated with liver fibrosis and cholangiocarcinoma. Further understanding of the pathogenesis of C. sinensis, especially liver fibrosis, could help us develop novel strategies for controlling clonorchiasis. Poly (ADP-ribose) polymerase-1 (PARP-1) can induce cellular parthanatos which is reported to be involved in liver fibrosis. Currently, whether C. sinensis could activate PARP-1 signaling to induce parthanatos or whether parthanatos play a role in C. sinensis-induced liver fibrosis is not clear. In the present study, the expression of PARP-1 and parthanatos indicators were detected in C. sinensis-infected mouse liver and in human intrahepatic biliary epithelial cells (HiBEpiCs) incubated with excretory/secretory products (ESPs) of C. sinensis. To explore the role of PARP-1 in C. sinensis infection, PARP-1 inhibitor NMS-P118 was used to block PARP-1 expression in vivo and vitro. The mortality rate, body weight, worm load, liver and bile duct lesions as well as PARP-1 and parthanatos indicators in C57BL/6 mice infected with C. sinensis, or in HiBEpiCs incubated with C. sinensis ESPs and NMS-P118 were analyzed and compared to the group without NMS-P118. The results showed that C. sinensis infection induced the activation of PARP-1 signaling as well as the translocation of AIF and MIF into the nucleus in mouse liver. ESPs of C. sinensis could induce PARP-1 up-regulation, ATP depletion and DNA damage in HiBEpiCs, indicating that C. sinensis could induce parthanatos. Inhibiting PARP-1 with NMS-P118 significantly reduced liver fibrosis and the number of larvae, increased the survival rate and body weight gain of the mice infected with C. sinensis. In addition, NMS-P118 decreased the expression of PARP-1 and alleviated ATP depletion as well as DNA damage in HiBEpiCs incubated with ESPs of C. sinensis. Our data indicated that C. sinensis and its ESPs could activate PARP-1 signaling to induce cellular parthanatos. NMS-P118 treatment alleviated liver fibrosis and promoted survival of the mice by inhibiting PARP-1, which suggested that PARP-1 could be used as a potential therapeutic target against clonorchiasis.

The significant mechanism and treatments of cell death in heatstroke

With global warming, extreme environmental heat is becoming a social issue of concern, which can cause adverse health results including heatstroke (HS). Severe heat stress is characterized by cell death of direct heat damage, excessive inflammatory responses, and coagulation disorders that can lead to multiple organ dysfunction (MODS) and even death. However, the significant pathophysiological mechanism and treatment of HS are still not fully clear. Various modes of cell death, including apoptosis, pyroptosis, ferroptosis, necroptosis and PANoptosis are involved in MODS induced by heatstroke. In this review, we summarized molecular mechanism, key transcriptional regulation as for HSF1, NRF2, NF-κB and PARP-1, and potential therapies of cell death resulting in CNS, liver, intestine, reproductive system and kidney injury induced by heat stress. Understanding the mechanism of cell death provides new targets to protect multi-organ function in HS.

Heat stroke: Pathogenesis, diagnosis, and current treatment

Recently, the incidence of heat-related illnesses has exhibited a steadily upward trend, which is closely associated with several environmental factors such as climate change and air pollution. The progression of heat-related illnesses is a continuous process and can progress to the terminal period when it transforms into heat stroke, the most severe form. Heat stroke is markedly by a core body temperature above 40°C and central nervous system dysfunction. Current knowledge suggests that the pathogenesis of heat stroke is complex and varied, including inflammatory response, oxidative stress, cell death, and coagulation dysfunction. This review consolidated recent research progress on the pathophysiology and pathogenesis of heat stroke, with a focus on the related molecular mechanisms. In addition, we reviewed common strategies and sorted out the drugs in various preclinical stages for heat stroke, aiming to offer a comprehensive research roadmap for more in-depth researches into the mechanisms of heat stroke and the reduction in the mortality of heat stroke in the future.

The pathogenesis and therapeutic strategies of heat stroke-induced liver injury

Heat stroke (HS) is a life-threatening systemic disease characterized by an elevated core body temperature of more than 40 ℃ and subsequent multiple organ dysfunction syndrome. With the growing frequency of global heatwaves, the incidence rate of HS has increased significantly, which has caused a huge burden on people's lives and health. Liver injury is a well-documented complication of HS and usually constitutes the direct cause of patient death. In recent years, a lot of research has been carried out on the pathogenesis and treatment strategies of HS-induced liver injury. In this review, we summarized the important pathogenesis of HS-induced liver injury that has been confirmed so far. In addition to the comprehensive effect of systemic factors such as heat cytotoxicity, coagulopathy, and systemic inflammatory response syndrome, excessive hepatocyte cell pyroptosis, dysfunction of Kupffer cells, abnormal expression of heat shock protein expression, and other factors are also involved in the pathogenesis of HS-induced liver injury. Furthermore, we have also established the current therapeutic strategies for HS-induced liver injury. Our study is of great significance in promoting the understanding of the pathogenesis and treatment of HS-induced liver injury.

Nicotinamide and heat preconditioning - Effects on hepatic HSP70, carbohydrate and oxidative disturbances in STZ-induced diabetic rats

OBJECTIVE

Nicotinamide (NA) is known to have antioxidant potential and partially to protect insulin-secreting cells against diabetogenic agent STZ (streptozotocin). In a combination to heat stress (HS), NA is also known to induce heat-shock proteins (HSPs) production. Heat preconditioning (HP) and HSPs have cytoprotective effects against development of cellular injury caused by application of subsequent stressor. We aimed to determine if pretreatment with NA and HP (as HSP70 -inducers) can affect STZ-induced diabetic disturbances in rats.

METHODS

NA-pretreatment (250 mg/kg b.w., 7 days) and heat preconditioning (41 ± 1 °C, 45 min) of diabetic rats was performed. The changes in hepatic carbohydrate- and antioxidative-related enzymes and substrates were investigated.

RESULTS

NA-pretreatment, alone or in combination with HS, resulted in significant increase of HSP70 concentration in the liver of control and diabetic rats. Compared to diabetic controls, pretreatment with NA, in combination with HP, resulted in decrease of blood and liver glucose, increase of glycogen and glucose-6-phosphate level, increase of glycogenolytic/glycolytic enzymes, decrease of gluconeogenic enzymes, as well as an increase of glutathione content and glutathione peroxidase, decrease of glutathione reductase and catalase activities.

CONCLUSIONS

NA is a potent HSP70 coinducer, alone or in a combination with HS in the liver of both control and diabetic rats. Pretreatment with NA, accompanied by HP, has a pronounced corrective effect on STZ-induced diabetes disturbances in the key hepatic carbohydrate- and antioxidative-related parameters. It seems that this corrective effect is based on the increased production of hepatic HSP70.

Inflammation-induced DNA damage, mutations and cancer

The relationships between inflammation and cancer are varied and complex. An important connection linking inflammation to cancer development is DNA damage. During inflammation reactive oxygen and nitrogen species (RONS) are created to combat pathogens and to stimulate tissue repair and regeneration, but these chemicals can also damage DNA, which in turn can promote mutations that initiate and promote cancer. DNA repair pathways are essential for preventing DNA damage from causing mutations and cytotoxicity, but RONS can interfere with repair mechanisms, reducing their efficacy. Further, cellular responses to DNA damage, such as damage signaling and cytotoxicity, can promote inflammation, creating a positive feedback loop. Despite coordination of DNA repair and oxidative stress responses, there are nevertheless examples whereby inflammation has been shown to promote mutagenesis, tissue damage, and ultimately carcinogenesis. Here, we discuss the DNA damage-mediated associations between inflammation, mutagenesis and cancer.

Poly(ADP-Ribose) Polymerase 1 Promotes the Human Heat Shock Response by Facilitating Heat Shock Transcription Factor 1 Binding to DNA

The heat shock response (HSR) is characterized by the rapid and robust induction of heat shock proteins (HSPs), including HSP70, in response to heat shock and is regulated by heat shock transcription factor 1 (HSF1) in mammalian cells. Poly(ADP-ribose) polymerase 1 (PARP1), which can form a complex with HSF1 through the scaffold protein PARP13, has been suggested to be involved in the HSR. However, its effects on and the regulatory mechanisms of the HSR are not well understood. Here we show that prior to heat shock, the HSF1-PARP13-PARP1 complex binds to the HSP70 promoter. In response to heat shock, activated and auto-PARylated PARP1 dissociates from HSF1-PARP13 and is redistributed throughout the HSP70 locus. Remarkably, chromatin in the HSP70 promoter is initially PARylated at high levels and decondensed, whereas chromatin in the gene body is moderately PARylated afterwards. Activated HSF1 then binds to the promoter efficiently and promotes the HSR. Chromatin PARylation and HSF1 binding to the promoter are also facilitated by the phosphorylation-dependent dissociation of PARP13. Furthermore, the HSR and proteostasis capacity are reduced by pretreatment with genotoxic stresses, which disrupt the ternary complex. These results illuminate one of the priming mechanisms of the HSR that facilitates the binding of HSF1 to DNA during heat shock.

Heat Stress Induces Extended Plateau of Hsp70 Accumulation--A Possible Cytoprotection Mechanism in Hepatic Cells

The relevance of heat preconditioning resides in its ability to protect cells from different kinds of injury by induction of heat shock proteins, a process in which the intensity of heat stress (HS) and duration of subsequent recovery are vital. This study evaluates the effects of moderate HS (45 min/43°C) and the time-dependent changes during recovery period of HSP70, Bcl-2 and p53 gene and protein expression in HepG2 cells. We also evaluated the effects of 0.4 mM aspirin (ASA) as a potential pharmacological co-inducer of HSP, both alone and in a combination with HS (ASA + HS). HS alone and ASA + HS caused a major up-regulation of HSP70 mRNA in the first 2 h, while HSP70 protein increased gradually and was especially abundant from 2 h to 24 h. Regarding Bcl-2, all treatments rendered similar results: gene expression was down-regulated in the first 2 h, after which there was protein elevation (12-48 h after HS). mRNA expression of p53 in HS- and (ASA + HS)-cells was down-regulated in the first 12 h. The immediate decrease of p53 protein after HS was followed by a biphasic increase. In conclusion, 0.4 mM ASA + HS does not act as a co-inducer of HSP70 in HepG2 cells, but promotes Bcl-2 protein expression during prolonged treatment. Our suggestion is that hepatic cells are most vulnerable in the first 2-6 h, but may have a high capacity for combating stress 12-24 h after HS. Finally, short-term exposure HS might be a "physiological conditioner" for liver cells to accumulate HSP and Bcl-2 proteins and thus obtain cytoprotection against an additional stress.

Synergistic cytotoxicity of the poly (ADP-ribose) polymerase inhibitor ABT-888 and temozolomide in dual-drug targeted magnetic nanoparticles

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is associated with a poor prognosis because of a lack of effective treatment options. The objective of this study was to examine a new strategy for HCC treatment, namely the use of poly (ADP-ribose) polymerase 1 (PARP-1) inhibitor (ABT-888) together with Temozolomide (TMZ) incorporated onto magnetic nanoparticles.

METHODS

Magnetic Fe3 O4 /Fe cores were encapsulated within a silica shell to facilitate the simultaneous incorporation of ABT-888 and TMZ. In vitro tests were performed with HepG2, Hep3B and PLC-PRF-5 liver tumoural cell lines and with WRL-68 liver non-tumoural cells.

RESULTS

The magnetic nanocarriers were loaded simultaneously with ABT-888 and TMZ. High stability and extended release were achieved in culture medium. Confocal microscopy images showed that drug-loaded particles were uptaken and accumulated into the cytoplasm of liver tumoural cells, inducing the following effects: G2/M cell cycle arrest (P < 0.05), accumulation of DNA damage (P < 0.05), mitochondrial depolarization (P < 0.01), reduction in BCL-xL, FOS, JUND gene expression (P < 0.05), PARP-1 fragmentation, Caspase-3 activation and apoptotic cell death (P < 0.05). Interestingly, drugs loaded onto nanoparticles exhibited better efficiency than free drugs (cell death triggered by drug delivery nanosystem: 53.5% vs. 34.5% by free drugs, P = 0.01).

CONCLUSIONS

These magnetic nanocompounds are able to incorporate both drugs simultaneously, enter the tumour cells and release them. ABT-888/TMZ/NPs decrease the transcription of key genes involved in tumour survival and induce apoptotic cell death in a more effective manner than is achieved by free drugs.

Poly(ADP-ribose) polymerase 1-sirtuin 1 functional interplay regulates LPS-mediated high mobility group box 1 secretion

Pathophysiological conditions that lead to the release of the prototypic damage-associated molecular pattern molecule high mobility group box 1 (HMGB1) also result in activation of poly(ADP-ribose) polymerase 1 (PARP1; now known as ADP-ribosyl transferase 1 [ARTD1]). Persistent activation of PARP1 promotes energy failure and cell death. The role of poly(ADP-ribosyl)ation in HMGB1 release has been explored previously; however, PARP1 is a versatile enzyme and performs several other functions including cross-talk with another nicotinamide adenine dinucleotide- (NAD(+)) dependent member of the Class III histone deacetylases (HDACs), sirtuin-1 (SIRT1). Previously, it has been shown that the hyperacetylation of HMGB1 is a seminal event prior to its secretion, a process that also is dependent on HDACs. Therefore, in this study, we seek to determine if PARP1 inhibition alters LPS-mediated HMGB1 hyperacetylation and subsequent secretion due to its effect on SIRT1. We demonstrate in an in vitro model that LPS treatment leads to hyperacetylated HMGB1 with concomitant reduction in nuclear HDAC activity. Treatment with PARP1 inhibitors mitigates the LPS-mediated reduction in nuclear HDAC activity and decreases HMGB1 acetylation. By utilizing an NAD(+)-based mechanism, PARP1 inhibition increases the activity of SIRT1. Consequently, there is an increased nuclear retention and decreased extracellular secretion of HMGB1. We also demonstrate that PARP1 physically interacts with SIRT1. Further confirmation of this data was obtained in a murine model of sepsis, that is, administration of PJ-34, a specific PARP1 inhibitor, led to decreased serum HMGB1 concentrations in mice subjected to cecal ligation and puncture (CLP) as compared with untreated mice. In conclusion, our study provides new insights in understanding the molecular mechanisms of HMGB1 secretion in sepsis.

Glucagon-Like Peptide 1 Protects against Hyperglycemic-Induced Endothelial-to-Mesenchymal Transition and Improves Myocardial Dysfunction by Suppressing Poly(ADP-Ribose) Polymerase 1 Activity

Under high glucose conditions, endothelial cells respond by acquiring fibroblast characteristics, that is, endothelial-to-mesenchymal transition (EndMT), contributing to diabetic cardiac fibrosis. Glucagon-like peptide-1 (GLP-1) has cardioprotective properties independent of its glucose-lowering effect. However, the potential mechanism has not been fully clarified. Here we investigated whether GLP-1 inhibits myocardial EndMT in diabetic mice and whether this is mediated by suppressing poly(ADP-ribose) polymerase 1 (PARP-1). Streptozotocin diabetic C57BL/6 mice were treated with or without GLP-1 analog (24 nmol/kg daily) for 24 wks. Transthoracic echocardiography was performed to assess cardiac function. Human aortic endothelial cells (HAECs) were cultured in normal glucose (NG) (5.5 mmol/L) or high glucose (HG) (30 mmol/L) medium with or without GLP-1analog. Immunofluorescent staining and Western blot were performed to evaluate EndMT and PARP-1 activity. Diabetes mellitus attenuated cardiac function and increased cardiac fibrosis. Treatment with the GLP-1 analog improved diabetes mellitus-related cardiac dysfunction and cardiac fibrosis. Immunofluorescence staining revealed that hyperglycemia markedly increased the percentage of von Willebrand factor (vWF)(+)/alpha smooth muscle actin (α-SMA)(+) cells in total α-SMA(+) cells in diabetic hearts compared with controls, which was attenuated by GLP-1 analog treatment. In cultured HAECs, immunofluorescent staining and Western blot also showed that both GLP-1 analog and PARP-1 gene silencing could inhibit the HG-induced EndMT. In addition, GLP-1 analog could attenuate PARP-1 activation by decreasing the level of reactive oxygen species (ROS). Therefore, GLP-1 treatment could protect against the hyperglycemia-induced EndMT and myocardial dysfunction. This effect is mediated, at least partially, by suppressing PARP-1 activation.

Therapeutic applications of PARP inhibitors: anticancer therapy and beyond

The aim of this article is to describe the current and potential clinical translation of pharmacological inhibitors of poly(ADP-ribose) polymerase (PARP) for the therapy of various diseases. The first section of the present review summarizes the available preclinical and clinical data with PARP inhibitors in various forms of cancer. In this context, the role of PARP in single-strand DNA break repair is relevant, leading to replication-associated lesions that cannot be repaired if homologous recombination repair (HRR) is defective, and the synthetic lethality of PARP inhibitors in HRR-defective cancer. HRR defects are classically associated with BRCA1 and 2 mutations associated with familial breast and ovarian cancer, but there may be many other causes of HRR defects. Thus, PARP inhibitors may be the drugs of choice for BRCA mutant breast and ovarian cancers, and extend beyond these tumors if appropriate biomarkers can be developed to identify HRR defects. Multiple lines of preclinical data demonstrate that PARP inhibition increases cytotoxicity and tumor growth delay in combination with temozolomide, topoisomerase inhibitors and ionizing radiation. Both single agent and combination clinical trials are underway. The final part of the first section of the present review summarizes the current status of the various PARP inhibitors that are in various stages of clinical development. The second section of the present review summarizes the role of PARP in selected non-oncologic indications. In a number of severe, acute diseases (such as stroke, neurotrauma, circulatory shock and acute myocardial infarction) the clinical translatability of PARP inhibition is supported by multiple lines of preclinical data, as well as observational data demonstrating PARP activation in human tissue samples. In these disease indications, PARP overactivation due to oxidative and nitrative stress drives cell necrosis and pro-inflammatory gene expression, which contributes to disease pathology. Accordingly, multiple lines of preclinical data indicate the efficacy of PARP inhibitors to preserve viable tissue and to down-regulate inflammatory responses. As the clinical trials with PARP inhibitors in various forms of cancer progress, it is hoped that a second line of clinical investigations, aimed at testing of PARP inhibitors for various non-oncologic indications, will be initiated, as well.

Signaling mechanism of poly(ADP-ribose) polymerase-1 (PARP-1) in inflammatory diseases

Poly(ADP-ribosyl)ation, attaching the ADP-ribose polymer chain to the receptor protein, is a unique posttranslational modification. Poly(ADP-ribose) polymerase-1 (PARP-1) is a well-characterized member of the PARP family. In this review, we provide a general update on molecular structure and structure-based activity of this enzyme. However, we mainly focus on the roles of PARP-1 in inflammatory diseases. Specifically, we discuss the signaling pathway context that PARP-1 is involved in to regulate the pathogenesis of inflammation. PARP-1 facilitates diverse inflammatory responses by promoting inflammation-relevant gene expression, such as cytokines, oxidation-reduction-related enzymes, and adhesion molecules. Excessive activation of PARP-1 induces mitochondria-associated cell death in injured tissues and constitutes another mechanism for exacerbating inflammation.

Small interfering RNA mediated Poly (ADP-ribose) Polymerase-1 inhibition upregulates the heat shock response in a murine fibroblast cell line

Poly (ADP-ribose) polymerase-1 (PARP-1) is a highly conserved multifunctional enzyme, and its catalytic activity is stimulated by DNA breaks. The activation of PARP-1 and subsequent depletion of nicotinamide adenine dinucleotide (NAD⁺) and adenosine triphosphate (ATP) contributes to significant cytotoxicity in inflammation of various etiologies. On the contrary, induction of heat shock response and production of heat shock protein 70 (HSP-70) is a cytoprotective defense mechanism in inflammation. Recent data suggests that PARP-1 modulates the expression of a number of cellular proteins at the transcriptional level. In this study, small interfering RNA (siRNA) mediated PARP-1 knockdown in murine wild-type fibroblasts augmented heat shock response as compared to untreated cells (as evaluated by quantitative analysis of HSP-70 mRNA and HSP-70 protein expression). These events were associated with increased DNA binding of the heat shock factor-1 (HSF-1), the major transcription factor of the heat shock response. Co-immunoprecipitation experiments in nuclear extracts of the wild type cells demonstrated that PARP-1directly interacted with HSF-1. These data demonstrate that, in wild type fibroblasts, PARP-1 plays a pivotal role in modulating the heat shock response both through direct interaction with HSF-1 and poly (ADP-ribosylation).

PARP inhibitors: new tools to protect from inflammation

Poly(ADP-ribosylation) consists in the conversion of β-NAD(+) into ADP-ribose, which is then bound to acceptor proteins and further used to form polymers of variable length and structure. The correct turnover of poly(ADP-ribose) is ensured by the concerted action of poly(ADP-ribose) polymerase (PARP) and poly(ADP-ribose) glycohydrolase (PARG) enzymes, which are responsible for polymer synthesis and degradation, respectively. Despite the positive role of poly(ADP-ribosylation) in sensing and repairing DNA damage, generated also by ROS, PARP over-activation could allow NAD depletion and consequent necrosis, thus leading to an inflammatory condition in many diseases. In this respect, inhibition of PARP enzymes could exert a protective role towards a number of pathological conditions; i.e. the combined treatment of tumors with PARP inhibitors/anticancer agents proved to have a beneficial effect in cancer therapy. Thus, pharmacological inactivation of poly(ADP-ribosylation) could represent a novel therapeutic strategy to limit cellular injury and to attenuate the inflammatory processes that characterize many disorders.

Inhibition of poly adenosine diphosphate-ribose polymerase decreases hepatocellular carcinoma growth by modulation of tumor-related gene expression

Hepatocellular carcinoma (HCC) is associated with a poor prognosis due to a lack of effective treatment options. In HCC a significant role is played by DNA damage and the inflammatory response. Poly (ADP-ribose) polymerase-1 (PARP-1) is an important protein that regulates both these mechanisms. The objective of this study was to examine the effect of pharmacology PARP-1 inhibition on the reduction of tumor volume of HCC xenograft and on the hepatocarcinogenesis induced by diethyl-nitrosamine (DEN). Pharmacologic PARP-1 inhibition with DPQ greatly reduces tumor xenograft volume with regard to a nontreated xenograft (394 mm(3) versus 2,942 mm(3), P < 0.05). This observation was paralleled by reductions in xenograft mitosis (P = 0.02) and tumor vasculogenesis (P = 0.007, confirmed by in vitro angiogenesis study), as well as by an increase in the number of apoptotic cells in DPQ-treated mice (P = 0.04). A substantial difference in key tumor-related gene expression (transformed 3T3 cell double minute 2 [MDM2], FLT1 [vascular endothelial growth factor receptor-1, VEGFR1], epidermal growth factor receptor [EPAS1]/hypoxia-inducible factor 2 [HIF2A], EGLN1 [PHD2], epidermal growth factor receptor [EGFR], MYC, JUND, SPP1 [OPN], hepatocyte growth factor [HGF]) was found between the control tumor xenografts and the PARP inhibitor-treated xenografts (data confirmed in HCC cell lines using PARP inhibitors and PARP-1 small interfering RNA [siRNA]). Furthermore, the results obtained in mice treated with DEN to induce hepatocarcinogenesis showed, after treatment with a PARP inhibitor (DPQ), a significant reduction both in preneoplastic foci and in the expression of preneoplastic markers and proinflammatory genes (Gstm3, Vegf, Spp1 [Opn], IL6, IL1b, and Tnf), bromodeoxyuridine incorporation, and NF-kappaB activation in the initial steps of carcinogenesis (P < 0.05).

CONCLUSION

This study shows that PARP inhibition is capable of controlling HCC growth and preventing tumor vasculogenesis by regulating the activation of different genes involved in tumor progression.

Dexamethasone induces a heat-stress response that ameliorates the conformational consequences on antithrombin of L-asparaginase treatment

BACKGROUND

L-asparaginase (L-ASP) treatment of patients with acute lymphoblastic leukemia causes a severe antithrombin deficiency by intracellular retention of this serpin within the endoplasmic reticulum (ER) of hepatic cells, and a subsequent risk of thrombosis. Interestingly, co-administration of dexamethasone with L-ASP seems to reduce the risk of thrombosis.

OBJECTIVES

We have investigated the effect of two corticoids, dexamethasone and prednisone, on the conformational consequences of L-ASP treatment on antithrombin.

PATIENTS/METHODS

Levels, activity, conformation and immunohistological features of antithrombin were studied in patients, cell and mice models. Because of the importance of the steroid receptor-heat stress response (HSR) axis, and the role of unfolded protein response (UPR) in conformational diseases, we also evaluated Hsp27, Hsp70, Hsp90, HSF-1 and ER chaperons (Grp78 and Grp94).

RESULTS

In all models, L-ASP alone or in combination with prednisone caused the intracellular retention of antithrombin associated with a severe deficiency. In contrast, the combination of L-ASP with dexamethasone ameliorated both the deficiency and intracellular retention of the serpin, which is associated with increased expression of heat shock proteins and ER-chaperons.

CONCLUSIONS

These results suggest a protective effect of dexamethasone on the conformational consequences of L-ASP on antithrombin as a result of exacerbated HSR and UPR that help to explain the reduced risk of thrombosis reported in patients that follow this scheme of treatment.