Thrombin Receptor-Activating Protein (TRAP)-Activated Akt Is Involved in the Release of Phosphorylated-HSP27 (HSPB1) from Platelets in DM Patients

Relationship between the Responsiveness of Amyloid β Protein to Platelet Activation by TRAP Stimulation and Brain Atrophy in Patients with Diabetes Mellitus

Type 2 DM is a risk factor for dementia, including Alzheimer's disease (AD), and is associated with brain atrophy. Amyloid β protein (Aβ) deposition in the brain parenchyma is implicated in the neurodegeneration that occurs in AD. Platelets, known as abundant storage of Aβ, are recognized to play important roles in the onset and progression of AD. We recently showed that Aβ negatively regulates platelet activation induced by thrombin receptor-activating protein (TRAP) in healthy people. In the present study, we investigated the effects of Aβ on the TRAP-stimulated platelet activation in DM patients, and the relationship between the individual responsiveness to Aβ and quantitative findings of MRI, the volume of white matter hyperintensity (WMH)/intracranial volume (IC) and the volume of parenchyma (PAR)/IC. In some DM patients, Aβ reduced platelet aggregation induced by TRAP, while in others it was unchanged or rather enhanced. The TRAP-induced levels of phosphorylated-Akt and phosphorylated-HSP27, the levels of PDGF-AB and the released phosphorylated-HSP27 correlated with the degree of platelet aggregability. The individual levels of not WMH/IC but PAR/IC was correlated with those of TRAP-stimulated PDGF-AB release. Collectively, our results suggest that the reactivity of TRAP-stimulated platelet activation to Aβ differs in DM patients from healthy people. The anti-suppressive feature of platelet activation to Aβ might be protective for brain atrophy in DM patients.

Mass cytometry of platelet-rich plasma: a new approach to analyze platelet surface expression and reactivity

Mass cytometry (CyTOF) is a new technology that allows the investigation of protein expression at single cell level with high resolution. While several protocols are available to investigate leukocyte expression, platelet staining and analysis with CyTOF have been described only from whole blood. Moreover, available protocols do not allow sample storage but require fresh samples to be obtained, processed, and measured immediately. We provide a structured and reproducible method to stain platelets from platelet-rich plasma to study thrombocyte protein expression and reactivity using mass cytometry. With our method, it is possible to acquire a large number of events allowing deep bioinformatic investigation of platelet expression heterogeneity. Integrated in our protocol is also a previously established freezing protocol that allows the storage of stained samples and to delay their measurement. Finally, we provide a structured workflow using different platelet stimulators and a freely available bioinformatic pipeline to analyze platelet expression. Our protocol unlocks the potential of CyTOF analysis for studying platelet biology in health and disease.

Heat shock protein 27 activity is linked to endothelial barrier recovery after proinflammatory GPCR-induced disruption

Vascular inflammation causes endothelial barrier disruption and tissue edema. Several inflammatory mediators act through G protein–coupled receptors (GPCRs), including protease-activated receptor-1 (PAR1), to elicit inflammatory responses. The activation of PAR1 by its ligand thrombin stimulates proinflammatory, p38 mitogen-activated protein kinase (MAPK) signaling that promotes endothelial barrier disruption. Through mass spectrometry phosphoproteomics, we identified heat shock protein 27 (HSP27), which exists as a large oligomer that binds to actin, as a promising candidate for the p38-mediated regulation of barrier integrity. Depletion of HSP27 by siRNA enhanced endothelial cell barrier permeability and slowed recovery after thrombin stimulation. We further showed that two effector kinases of p38 MAPK, MAPKAPK2 (MK2) and MAPKAPK3 (MK3), differentially phosphorylated HSP27 at Ser15, Ser78, and Ser82. Whereas inhibition of thrombin-stimulated p38 activation blocked HSP27 phosphorylation at all three sites, inhibition of MK2 reduced the phosphorylation of only Ser15 and Ser78. Inhibition of both MK2 and MK3 was necessary to attenuate Ser82 phosphorylation. Thrombin-stimulated p38-MK2-MK3 signaling induced HSP27 oligomer disassembly. However, a phosphorylation-deficient mutant of HSP27 exhibited defective oligomer disassembly and altered the dynamics of barrier recovery after thrombin stimulation. Moreover, blocking HSP27 oligomer reassembly with the small-molecule inhibitor J2 enhanced endothelial barrier permeability in vitro and vascular leakage in vivo in response to PAR1 activation. These studies reveal the distinct regulation of HSP27 phosphorylation and function induced by the GPCR-stimulated p38-MK2-MK3 signaling axis that controls the dynamics of endothelial barrier recovery in vitro and vascular leakage in vivo.

Small Heat Shock Proteins HSP10 and HSP27 in the Left Ventricular Myocardium in Rats with Arterial Hypertension and Insulin-Dependent Diabetes Mellitus

We studied the expression of small heat shock proteins HSP10 and HSP27 in left ventricular cardiomyocytes in animals with arterial hypertension, insulin-dependent diabetes mellitus, and their combination. The experiment was performed on 38-week-old male Wistar-Kyoto and 38-57-week-old SHR (spontaneously hypertensive) rats. Insulin-dependent diabetes mellitus was modeled by single parenteral injection of streptozotocin (65 mg/kg). Expression of HSP10 and HSP27 in left ventricular cardiomyocytes was evaluated by immunohistochemical assay. It was found that the content of HSP10 in the left ventricular cardiomyocytes decreased in comparison with the control in case of isolated diabetes mellitus and, on the contrary, increased in case of arterial hypertension combined with diabetes mellitus. The intensity of HSP27 expression decreased in case of 38-week arterial hypertension and a combination of arterial hypertension with diabetes mellitus. However, in case of 57-week arterial hypertension we observed an increase in the content of HSP27 in cardiomyocytes.

The release of phosphorylated-HSP27 from activated platelets of obstructive sleep apnea syndrome (OSAS) patients

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is a well known risk of arterial thrombosis that results in cardiovascular morbidity. It has been reported that platelet aggregability is enhanced in patients with OSAS. In the present study, we investigated whether phosphorylated-HSP27 is released from the activated platelets of OSAS patients.

METHODS

Patients diagnosed with OSAS (n = 21) were recruited, and platelet-rich plasma (PRP) was stimulated by ADP, ristosetin, collagen, and thrombin receptor-activating peptide. Platelet aggregation was measured using an aggregometer with a laser-scattering system. The levels of protein phosphorylation and the released levels of phosphorylated-HSP27 were determined by Western blot analysis and an ELISA, respectively.

RESULTS

The phosphorylation of HSP27 in the platelets was induced by the stimulators. The released levels of phosphorylated-HSP27 was correlated with the levels of phosphorylated-HSP27 stimulated by ADP or collagen. The levels of ADP-induced phosphorylated-HSP27 were correlated with those of both phosphorylated-protein kinase B (Akt) and phosphorylatd-p38 mitogen-activated protein kinase; however, the levels of phosphorylated-HSP27 stimulated by collagen were correlated with phosphorylated-Akt levels only. The ED₅₀ value of ADP on the platelet aggregation in OSAS (1.067 ± 0.128 μM) was lower than that in healthy subjects (1.778 ± 0.122 μM) and was inversely correlated with both the value of minimum SpO₂ and the released level of phosphorylated-HSP27 stimulated by ADP.

CONCLUSION

The results strongly suggest that phosphorylated-HSP27 is released from the activated platelets of OSAS patients.

Hydroxysafflor yellow A (HSYA) alleviates apoptosis and autophagy of neural stem cells induced by heat stress via p38 MAPK/MK2/Hsp27-78 signaling pathway

This study aimed to explore mechanisms of the effects of hydroxysafflor yellow A (HSYA) on neural stem cells (NSCs) after heat stress (HS). Rat NSCs cells were cultured at 42 °C to impose heat stress. Cell counting kit-8 and Edu assay were used to analyze NSC proliferation. Annexin V/PI apoptosis kit was used to detect NSC apoptosis. Expression and phosphorylation of autophagy and apoptosis-associated proteins were determined by western blotting. We showed that HSYA significantly promoted proliferation and attenuated apoptosis of NSCs after heat stress. HSYA also increased Bcl-2 expression but decreased the expression of Bax and cleaved caspase-3 in NSCs induced by heat stress. In addition, HSYA decreased p38 and Hsp27-78 phosphorylation and MK-2 expression after heat stress, which was consistent with NSCs treated with SB203850 treatment or p38 knockdown. Furthermore, we demonstrated that heat stress increased LC3-II expression and mTOR phosphorylation, and decreased the expression of p62 in NSCs, while HSYA, SB203850 treatment or p38 knockdown reversed these alterations. In conclusion, HSYA significantly reversed the apoptosis and autophagy of NSCs induced by heat stress (P < 0.05), via downregulating MK2 expression and p38 and Hsp27-78 phosphorylation.

HSP27 is a partner of JAK2-STAT5 and a potential therapeutic target in myelofibrosis

Heat shock protein 27 (HSP27/HSPB1) is a stress-inducible chaperone that facilitates cancer development by its proliferative and anti-apoptotic functions. The OGX-427 antisense oligonucleotide against HSP27 has been reported to be beneficial against idiopathic pulmonary fibrosis. Here we show that OGX-427 is effective in two murine models of thrombopoietin- and JAKV617F-induced myelofibrosis. OGX-427 limits disease progression and is associated with a reduction in spleen weight, in megakaryocyte expansion and, for the JAKV617F model, in fibrosis. HSP27 regulates the proliferation of JAK2V617F-positive cells and interacts directly with JAK2/STAT5. We also show that its expression is increased in both CD34⁺ circulating progenitors and in the serum of patients with JAK2-dependent myeloproliferative neoplasms with fibrosis. Our data suggest that HSP27 plays a key role in the pathophysiology of myelofibrosis and represents a new potential therapeutic target for patients with myeloproliferative neoplasms.

Myelofibrosis is a chronic degenerative disorder characterized by progressive bone marrow fibrosis. Here, the authors show that the chaperone HSP27 contributes to myelofibrosis via regulation of the JAK2/STAT5 pathway, and that antisense oligonucleotides targeting HSP27 are effective in two mouse models of the disease

An assessment of platelet parameters in different ethnic groups with hypertension subtypes and associated risk factors in Xinjiang, China

The goal of this study was to investigate platelet parameters in populations with hypertension subtypes among the Han, Uygur, and Kazakh ethnic groups and their associated risk factors in Xinjiang, northwestern China. In total, 9816 adult participants were recruited from a multiethnic, cross-sectional cardiovascular risk survey. Our results indicated that the platelet counts in Han, Uygur, and Kazakh participants with isolated systolic hypertension (ISH), isolated diastolic hypertension (IDH), and systolic diastolic hypertension (SDH) varied significantly (P < 0.001). Additionally, the mean platelet volume (MPV) in Han, Uygur, and Kazakh participants with ISH was significantly different (P < 0.05). Furthermore, the individual platelet parameters had different associated risk factors. For example, the risk factors for platelet counts were Uygur ethnicity, Kazakh ethnicity, drinking, ISH, diabetes, and high triglycerides (TGs). The risk factors for MPV were Uygur ethnicity, smoking, overweight, obesity, ISH, IDH, diabetes, and high TGs. Gender was a risk factor for abnormal plateletcrit (PCT) values. Only a low high-density lipoprotein cholesterol level was found to be a risk factor for platelet distribution width (PDW). We suggest that more attention should be paid to platelet parameters and the associated risk factors to reinforce the effect of antiplatelet therapy and to provide a clinical basis for preventing the occurrence of thrombosis complications and cerebro- and cardiovascular diseases effectively.

Ristocetin induces phosphorylated-HSP27 (HSPB1) release from the platelets of type 2 DM patients: Anti-platelet agent-effect on the release

It has been previously reported that HSP27 is released from platelets in type 2 diabetes mellitus (DM) patients according to phosphorylation. In the present study, we investigated the effect of ristocetin, a glycoprotein (GP)Ib/IX/V activator, on the release of HSP27 and the effect of anti-platelet agents, such as acetylsalicylic acid (ASA), on this release. Forty-six patients with type 2 DM were recruited, and classified into two groups depending on administration of anti-platelet agents, resulting in 31 patients without these agents (control group) and 15 patients with them (anti-platelet group). Ristocetin potently induced the aggregation of platelets in the two groups. Ristocetin-induced changes of the area under the curve of light transmittance and the ratio of the size of platelet aggregates in the anti-platelet group were slightly different from those in the control group. On the other hand, the levels of phosphorylated-HSP27 induced by ristocetin in the platelets from a patient of the anti-platelet group taking ASA were significantly lower than those from a patient of the control group. The levels of HSP27 release from the ristocetin-stimulated platelets were significantly correlated with the levels of phosphorylated-HSP27 in the platelets from patients in the two groups. The levels of HSP27 release and those of platelet-derived growth factor-AB (PDGF-AB) secretion stimulated by ristocetin in the anti-platelet group were lower than those in the control group. In addition, the levels of HSP27 release and those of PDGF-AB secretion stimulated by ADP in the anti-platelet group were lower than those in the control group. These results strongly suggest that anti-platelet agents inhibit the HSP27 release from platelets stimulated by ristocetin but not the aggregation in type 2 DM patients.

Heat Shock Proteins in Vascular Diabetic Complications: Review and Future Perspective

Heat shock proteins (HSPs) are a large family of proteins highly conserved throughout evolution because of their unique cytoprotective properties. Besides assisting protein refolding and regulating proteostasis under stressful conditions, HSPs also play an important role in protecting cells from oxidative stress, inflammation, and apoptosis. Therefore, HSPs are crucial in counteracting the deleterious effects of hyperglycemia in target organs of diabetes vascular complications. Changes in HSP expression have been demonstrated in diabetic complications and functionally related to hyperglycemia-induced cell injury. Moreover, associations between diabetic complications and altered circulating levels of both HSPs and anti-HSPs have been shown in clinical studies. HSPs thus represent an exciting therapeutic opportunity and might also be valuable as clinical biomarkers. However, this field of research is still in its infancy and further studies in both experimental diabetes and humans are required to gain a full understanding of HSP relevance. In this review, we summarize current knowledge and discuss future perspective.