HMGB1-induced activation of ER stress contributes to pulmonary artery hypertension in vitro and in vivo.

BACKGROUND: HMGB1 and ER stress have been considered to participate in the progression of pulmonary artery hypertension (PAH). However, the molecular mechanism underlying HMGB1 and ER stress in PAH remains unclear. This study aims to explore whether HMGB1 induces pulmonary artery smooth muscle cells (PASMCs) functions and pulmonary artery remodeling through ER stress activation. METHODS: Primary cultured PASMCs and monocrotaline (MCT)-induced PAH rats were applied in this study. Cell proliferation and migration were determined by CCK-8, EdU and transwell assay. Western blotting was conducted to detect the protein levels of protein kinase RNA-like endoplasmic reticulum kinase (PERK), activating transcription factor-4 (ATF4), seven in absentia homolog 2 (SIAH2) and homeodomain interacting protein kinase 2 (HIPK2). Hemodynamic measurements, immunohistochemistry staining, hematoxylin and eosin staining were used to evaluate the development of PAH. The ultrastructure of ER was observed by transmission electron microscopy. RESULTS: In primary cultured PASMCs, HMGB1 reduced HIPK2 expression through upregulation of ER stress-related proteins (PERK and ATF4) and subsequently increased SIAH2 expression, which ultimately led to PASMC proliferation and migration. In MCT-induced PAH rats, interfering with HMGB1 by glycyrrhizin, suppression of ER stress by 4-phenylbutyric acid or targeting SIAH2 by vitamin K3 attenuated the development of PAH. Additionally, tetramethylpyrazine (TMP), as a component of traditional Chinese herbal medicine, reversed hemodynamic deterioration and vascular remodeling by targeting PERK/ATF4/SIAH2/HIPK2 axis. CONCLUSIONS: The present study provides a novel insight to understand the pathogenesis of PAH and suggests that targeting HMGB1/PERK/ATF4/SIAH2/HIPK2 cascade might have potential therapeutic value for the prevention and treatment of PAH.

Effect of the regimen of Gaoshan Hongjingtian on the mechanism of poly (ADP-ribose) polymerase regulation of nuclear factor kappa B in the experimental diabetic retinopathy.

BACKGROUND: Poly(ADP-ribose) polymerase (PARP) plays an important role in the death of retinal capillary cells in diabetic retinopathy (DR) partly via its regulation of nuclear factor kappa B (NF-κB). The current study investigated the effect of the regimen of Gaoshan Hongjingtian (RG) on the mechanism of PARP regulation of NF-κB, and demonstrated the possible impact of the RG and Gaoshan Hongjingtian (Rhodiola sachalinensis, RS) on diabetic retinopathy. METHODS: Wistar rats were made diabetic by administering streptozotocin. They were then assigned to three groups at random. After 2 months, the three groups of these diabetic rats were treated with RS or RG, or untreated. Analyses of expression levels of PARP, NF-κB, and intercellular adhesion molecule-1 (ICAM-1) in the retinas of rats in different groups were performed by Western blotting and immunohistochemical assays, and mRNA levels of NF-κB and ICAM-1 were determined by real-time polymerase chain reaction (PCR). In addition, the basement membranes of capillaries in the rats' retinas were observed using electron microscopy, and diabetes-induced capillary degeneration (ghost pericytes and acellular capillaries) were quantitated. RESULTS: From the third month after the injection of streptozotocin, the diabetic rats were given daily RG, RS or tap water separately. The diabetic rats failed to gain weight compared with normal age-matched rats, whereas their glycated hemoglobin levels were significantly increased. After 5 months, the mRNA levels of NF-κB and ICAM-1 and the protein expression of PARP, NF-κB, and ICAM-1 were significantly increased in the retinas of diabetic rats in the untreated group compared with the nondiabetic controls. After 8 months, the number of degenerated retinal capillaries (ghost pericytes and acellular capillaries) was significantly increased in the diabetic rats in the untreated group compared with normal age-matched rats. RG and RS inhibited diabetes-induced over-expression of PARP, NF-κB, and ICAM-1 in the retinas of diabetic rats at the end of 5-month diabetic duration. Treatment using RG and RS significantly inhibited increases in the number of acellular capillaries and pericyte ghosts and suppressed the basement membrane thickening in the retinas of rats with diabetes for 8 months compared with the control diabetic rats. CONCLUSIONS: These results indicate that PARP plays an important role in the pathogenesis of diabetic retinopathy. RS and RG may have acted on the mechanism of PARP regulation of NF-κB, which suppressed the expression of NF-κB and ICAM-1, and led to the inhibition of retinal capillary degeneration.