YC-1 induces heat shock protein 70 expression and prevents oxidized LDL-mediated apoptosis in vascular smooth muscle cells

A role of Heat Shock Protein 70 in Photoreceptor Cell Death: Potential as a Novel Therapeutic Target in Retinal Degeneration

Retinal degenerative diseases (RDs) such as retinitis pigmentosa (RP) are a genetically heterogeneous group of disorders characterized by night blindness and peripheral vision loss, which caused by the dysfunction and death of photoreceptor cells. Although many causative gene mutations have been reported, the final common end stage is photoreceptor cell death. Unfortunately, no effective treatments or therapeutic agents have been discovered. Heat shock protein 70 (HSP70) is highly conserved and has antiapoptotic activities. A few reports have shown that HSP70 plays a role in RDs. Thus, we focused on the role of HSP70 in photoreceptor cell death. Using the N-methyl-N-nitrosourea (MNU)-induced photoreceptor cell death model in mice, we could examine two stages of the novel cell death mechanism; the early stage, including HSP70 cleavage through protein carbonylation by production of reactive oxygen species, lipid peroxidation and Ca(2+) influx/calpain activation, and the late stage of cathepsin and/or caspase activation. The upregulation of intact HSP70 expression by its inducer is likely to protect photoreceptor cells. In this review, we focus on the role of HSP70 and the novel cell death signaling process in RDs. We also describe candidate therapeutic agents for RDs.

The role of heat shock protein 70 in the protective effect of YC-1 on β-amyloid-induced toxicity in differentiated PC12 cells

Neurodegenerative brain disorders such as Alzheimer’s disease (AD) have been well investigated. However, significant methods for the treatment of the progression of AD are unavailable currently. Heat shock protein 70 (Hsp70) plays important roles in neural protection from stress by assisting cellular protein folding. In this study, we investigated the effect and the molecular mechanism of YC-1, an activator of guanylyl cyclase (GC), on Aβ_25–35-induced cytotoxicity in differentiated PC12 cells. The results of this study showed that Aβ_25–35 (10 µM) significantly increased p25 protein production in a pattern that was consistent with the increase in μ-calpain expression. Moreover, Aβ_25–35 significantly increased tau hyperphosphorylation and induced differentiated PC12 cell death. YC-1 (0.5–10 µM) prevented the cell death induced by Aβ_25–35. In addition, YC-1 (1, 10 µM) significantly blocked Aβ_25–35-induced μ-calpain expression and decreased the formation of p25 and tau hyperphosphorylation. Moreover, YC-1 (5–20 µM) alone or combined with Aβ_25–35 (10 µM) significantly increased the expression of Hsp70 in differentiated PC12 cells. The neuroprotective effect of YC-1 was significantly attenuated by an Hsp70 inhibitor (quercetin, 50 µM) or in PC12 cells transfected with an Hsp70 small interfering RNA. However, pretreatment of cells with the GC inhibitor ODQ (10 µM) did not affect the neuroprotective effect of YC-1 against Aβ_25–35 in differentiated PC12 cells. These results suggest that the neuroprotective effect of YC-1 against Aβ_25–35-induced toxicity is mainly mediated by the induction of Hsp70. Thus, YC-1 is a potential agent against AD.

The role of heat shock protein 70 in the protective effect of YC-1 on heat stroke rats

Heat stroke is a life-threatening illness characterized by an elevated core body temperature. Despite adequate lowering of the body temperature and support treatment of multiple organ-system function, heat stroke is often fatal. 3-(5'-Hydoxymethyl-2'-furyl)-1-benzyl-indazol (YC-1) been identified as an activator of soluble guanylate cyclase. To evaluate whether YC-1 protects multiple organ dysfunctions and improves survival during heat stroke and its mechanism. Male Sprague-Dawley rats untreated or treated with either YC-1 or quercetin (heat shock protein (Hsp) 70 inhibitor) were exposures to heat as a model of heat stroke. The mean arterial pressure (MAP), heart rate, rectal temperature (Tco), survival time, and plasma biochemical data, intracellular Hsp70 and heat shock factor-1 expression were measured. The value of MAP, heart rate and Tco of untreated heat stroke (HS) group were all significantly lower than that of normothermal (NT) group. Biochemical markers evidenced that liver and kidney injuries of HS group were significantly higher than that of NT groups. YC-1 (20mg/kg) pretreatment with heat stroke (YC-1+HS) group, the MAP and heart rate were return to normal, and the biochemical markers were all significantly recovered to normal. The survival time of HS group, NT group and YC-1+HS group were 21, 480, and 445 min, respectively. The expression of Hsp70 and HSF-1 in liver and renal of YC-1+HS group was significantly higher than that of HS group. All of the protective effects of YC-1 were all significantly suppressed when pretreated with quercetin (400mg/kg). Results indicate that YC-1 may improve survival due to induce Hsp70 overexpression.

Guanylate cyclase activator YC-1 enhances TRAIL-induced apoptosis in human epithelial ovarian carcinoma cells via activation of apoptosis-related proteins

To assess the ability of 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1) to promote apoptosis, we investigated the effect of YC-1 on tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in the human epithelial ovarian carcinoma cell lines. In OVCAR-3 and SK-OV-3 cell lines, we examined the stimulatory effect of YC-1 on TRAIL-induced apoptosis by monitoring cell death, nuclear damage, changes in apoptosis-related protein levels, activation of caspases and changes in the mitochondrial transmembrane potential. TRAIL induced a decrease in Bid, Bcl-2 and Bcl-xL protein levels, increase in cleaved Bid and Bax levels, loss of the mitochondrial transmembrane potential, cytochrome c release, activation of caspases (-8, -9 and -3) and an increase in the tumour suppressor p53 levels. YC-1 enhanced TRAIL-induced apoptosis-related protein activation, nuclear damage and cell death. Results from this study suggest that YC-1 may enhance the apoptotic effect of TRAIL on ovarian carcinoma cell lines by increasing the activation of the caspase-8- and Bid-dependent pathways and the mitochondria-mediated apoptotic pathway, leading to caspase activation. YC-1 may confer a benefit in TRAIL treatment of epithelial ovarian adenocarcinoma.

Heat-shock proteins in cardiovascular disease

Heat-shock proteins (HSPs) belong to a group of highly conserved families of proteins expressed by all cells and organisms and their expression may be constitutive or inducible. They are generally considered as protective molecules against different types of stress and have numerous intracellular functions. Secretion or release of HSPs has also been described, and potential roles for extracellular HSPs reported. HSP expression is modulated by different stimuli involved in all steps of atherogenesis including oxidative stress, proteolytic aggression, or inflammation. Also, antibodies to HSPs may be used to monitor the response to different types of stress able to induce changes in HSP levels. In the present review, we will focus on the potential implication of HSPs in atherogenesis and discuss the limitations to the use of HSPs and anti-HSPs as biomarkers of atherothrombosis. HSPs could also be considered as potential therapeutic targets to reinforce vascular defenses and delay or avoid clinical complications associated with atherothrombosis.

HSP70 protects intestinal epithelial cells from hypoxia/reoxygenation injury via a mechanism that involves the mitochondrial pathways

Though recent studies have reported the importance of several endogenous cytoprotective factors including heat shock protein 70 (HSP70) that protect intestinal epithelial cells (IECs) from the effects of stress and injury, the exact mechanism of HSP70 underlying cytoprotection against hypoxia/reoxygenation induced IEC injury remains unclear. The present study was designed to investigate the possible mechanisms by which HSP70 protected IECs against hypoxia/reoxygenation injury and focused on the effects of HSP70 on IEC apoptosis induced by hypoxia/reoxygenation injury. Recombinant adenoviruses (Ad-HSP70) were transfected into the intestinal epithelial cell line in vitro and then suffered from 90 min of hypoxia followed by 60 min of reoxygenation. The LDH leaking, apoptosis, and mitochondrial membrane potential (Psi(m)) were evaluated after hypoxia/reoxygenation. The expression of HSP70, cytochrome c and Bcl-2 protein was determined by Western blot or immunofluorescence analysis. The results show that HSP70 protein was highly expressed in the IECs at 48h following Ad-HSP70 transfection. HSP70 overexpression could reduce LDH leakage and cell apoptosis in IECs following hypoxia/reoxygenation injury. Furthermore, the overexpression of HSP70 significantly reversed the decrease of mitochondrial membrane potential and the release of mitochondrial cytochrome c in IECs during hypoxia/reoxygenation. HSP70 overexpression was also associated with the increasing expression of Bcl-2 protein in IECs during hypoxia/reoxygenation. We conclude that HSP70 protects IECs against hypoxia/reoxygenation induced apoptosis through increasing Bcl-2 expression, which in turn could inhibit the mitochondria-related apoptotic pathway that involves the disruption of the Psi(m) and release of cytochrome c from mitochondria.

Heat shock protein 70 is secreted from endothelial cells by a non-classical pathway involving exosomes

Emerging evidence suggests that a high level of circulating heat shock protein 70 (HSP70) correlates with a lower risk of vascular disease; however, the biological significance of this inverse relationship has not been explored. Herein, we report that oxidative low density lipoprotein (Ox-LDL) and homocysteine (Hcy) induce HSP70 release from endothelial cells. In rat endothelial cells, Ox-LDL and Hcy induced robust release of HSP70, independent of the classical route of endoplasmic reticulum/Golgi protein trafficking or the formation of lipid rafts. In contrast, Ox-LDL and Hcy significantly enhanced the exosomal secretory rate and increased the HSP70 content of exosomes. Exogenous HSP70 had no impact on LPS-, Ox-LDL- and Hcy-induced activation of endothelial cells, whereas HSP70 did activate monocytes alone, resulting in monocyte adhesion to endothelial cells. These results indicate that exosome-dependent secretion of HSP70 from endothelial cells provides a novel paracrine mechanism to regulate vascular endothelial functional integrity.

Combined application of camptothecin and the guanylate cyclase activator YC-1: Impact on cell death and apoptosis-related proteins in ovarian carcinoma cell lines

Camptothecin analogs and guanylate cyclase activator YC-1 [3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole] have been shown to induce apoptosis in cancer cells. However, the combined effect of camptothecin analogs and YC-1 on the viability of epithelial ovarian cancer cells remains uncertain. We assessed the combined effect of YC-1 on the camptothecin toxicity in the human epithelial ovarian carcinoma cell lines OVCAR-3 and SK-OV-3. Camptothecin and YC-1 induced apoptosis in OVCAR-3 and SK-OV-3 cells in a dose- and time-dependent manner. Both compounds induced nuclear damage, decreased Bid and Bcl-2 protein levels, enhanced cytochrome c release, activated caspase-3 and upregulated tumor suppressor p53. Camptothecin decreased Bax protein levels, whereas YC-1 increased Bax levels. YC-1 enhanced the camptothecin-induced changes in the apoptotic protein levels and increased apoptotic effect of camptothecin on ovarian carcinoma cell lines. The results suggested that YC-1 may enhance a camptothecin toxicity against ovarian carcinoma cell lines by increasing activation of the caspase-8 and Bid pathway as well as activation of the mitochondria-mediated apoptotic pathway, leading to cytochrome c release and subsequent caspase-3 activation. Combination of camptothecin analogs and YC-1 may provide a therapeutic benefit against ovarian adenocarcinoma.

HSP 70 and atherosclerosis--protector or activator?

BACKGROUND

Atherosclerosis and its complications represent the leading cause of morbidity and mortality. Heat shock protein 70 (HSP70) protects cellular elements from injury by reducing oxidation, inflammation and apoptosis and by refolding damaged proteins. HSP70 improves viability of stressed vascular smooth muscle cells, possibly via its chaperone functions. It has been proposed that the response mounted against bacterial HSPs results in an autoimmune reaction, which has the potential to cause complement-mediated endothelial injury, and hence accelerate atherogenesis.

OBJECTIVE

to examine the roles of HSPs in atherosclerosis.

METHODS

A literature review.

RESULTS/CONCLUSIONS

The role of HSPs in atherosclerosis is controversial. HSP60 probably acts as an autoantigen, and may trigger both cell- and antibody-mediated immune responses, while HSP70 is likely to be involved in cytoprotection. The significance of this inverse relation between HSP70 and atherosclerosis has not yet been elucidated. Whether HSPs will become therapeutic targets remains to be established.

NO-independent, haem-dependent soluble guanylate cyclase stimulators

The nitric oxide (NO) signalling pathway is altered in cardiovascular diseases, including systemic and pulmonary hypertension, stroke, and atherosclerosis. The vasodilatory properties of NO have been exploited for over a century in cardiovascular disease, but NO donor drugs and inhaled NO are associated with significant shortcomings, including resistance to NO in some disease states, the development of tolerance during long-term treatment, and non-specific effects such as post-translational modification of proteins. The development of pharmacological agents capable of directly stimulating the NO receptor, soluble guanylate cyclase (sGC), is therefore highly desirable. The benzylindazole compound YC-1 was the first sGC stimulator to be identified; this compound formed a lead structure for the development of optimized sGC stimulators with improved potency and specificity for sGC, including CFM-1571, BAY 41-2272, BAY 41-8543, and BAY 63-2521. In contrast to the NO- and haem-independent sGC activators such as BAY 58-2667, these compounds stimulate sGC activity independent of NO and also act in synergy with NO to produce anti-aggregatory, anti-proliferative, and vasodilatory effects. Recently, aryl-acrylamide compounds were identified independent of YC-1 as sGC stimulators; although structurally dissimilar to YC-1, they have a similar mode of action and promote smooth muscle relaxation. Pharmacological stimulators of sGC may be beneficial in the treatment of a range of diseases, including systemic and pulmonary hypertension, heart failure, atherosclerosis, erectile dysfunction, and renal fibrosis. An sGC stimulator, BAY 63-2521, is currently in clinical development as an oral therapy for patients with pulmonary hypertension. It has demonstrated efficacy in a proof-of-concept study, reducing pulmonary vascular resistance and increasing cardiac output from baseline. A full, phase 2 trial of BAY 63-2521 in pulmonary hypertension is underway.