HIMF deletion ameliorates acute myocardial ischemic injury by promoting macrophage transformation to reparative subtype

Appropriately manipulating macrophage M1/M2 phenotypic transition is a promising therapeutic strategy for tissue repair after myocardial infarction (MI). Here we showed that gene ablation of hypoxia-induced mitogenic factor (HIMF) in mice (Himf^−/− and HIMF^flox/flox;Lyz2-Cre) attenuated M1 macrophage-dominated inflammatory response and promoted M2 macrophage accumulation in infarcted hearts. This in turn reduced myocardial infarct size and improved cardiac function after MI. Correspondingly, expression of HIMF in macrophages induced expression of pro-inflammatory cytokines; the culturing medium of HIMF-overexpressing macrophages impaired the cardiac fibroblast viability and function. Furthermore, macrophage HIMF was found to up-regulate C/EBP-homologous protein (CHOP) expression, which exaggerated the release of pro-inflammatory cytokines via activating signal transducer of activator of transcription 1 (STAT1) and 3 (STAT3) signaling. Together these data suggested that HIMF promotes M1-type and prohibits M2-type macrophage polarization by activating the CHOP–STAT1/STAT3 signaling pathway to negatively regulate myocardial repair. HIMF might thus constitute a novel target to treat MI.

Mild hypothermia reduces endoplasmic reticulum stress-induced apoptosis and improves neuronal functions after severe traumatic brain injury

BACKGROUND

Mild hypothermia is wildly used in clinical treatment of traumatic brain injury (TBI). However, the effect of mild hypothermia on endoplasmic reticulum (ER) stress-induced apoptosis after severe TBI is still unknown.

METHODS

In the present study, we used BALB/c mice to investigate the efficacy of posttraumatic mild hypothermia in reducing ER stress. Severe TBI was induced by controlled cortical impact injury. Mild hypothermia treatment was performed immediately after surgery and maintained for 4 hr. The animals were euthanized at 1 and 7 days after severe TBI. The expression levels of ER stress marker proteins were evaluated using Western blot and immunofluorescence. Cell apoptosis rate was analyzed by TUNEL staining. Neuronal functions of the mice were assessed using rotarod test and Morris water maze.

RESULTS

Our results revealed that mild hypothermia significantly attenuated ER stress marker proteins, including p-eIF2α/eIF2α, ATF4, CHOP and IRE-1α, and reduced apoptosis rate in the pericontusion region at 1 and 7 days after severe TBI. Interestingly, mild hypothermia also prevented the translocation of CHOP into nucleus. In addition, posttraumatic mild hypothermia significantly improved neuronal functions after severe TBI.

CONCLUSIONS

Our findings illustrated that mild hypothermia could reduce ER stress-induced apoptosis and improve neuronal functions after severe traumatic brain injury.

Endoplasmic reticulum stress contributes to the pathogenesis of stress urinary incontinence in postmenopausal women

Objective

To investigate the relationship between endoplasmic reticulum stress (ERS) and the pathogenesis of stress urinary incontinence (SUI) in postmenopausal women.

Methods

Anterior vaginal wall tissue was collected from postmenopausal women with SUI and control subjects. Western blotting was performed for glucose-regulated protein (GRP78), inositol-requiring enzyme 1(IRE1), protein kinase-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), C/EBP-homologous protein (CHOP), and B-cell lymphoma 2 (Bcl-2). Additionally, mRNA expression levels of PERK, activating transcription factor 4 (ATF4), and CHOP were examined by real-time polymerase chain reaction.

Results

GRP78 protein and mRNA expression levels were significantly lower in women with SUI, compared with control subjects. PERK and p-PERK expression levels were higher in women with SUI than in control subjects. However, no differences in IRE1 or ATF6 expression levels were observed in either group. Notably, higher CHOP and lower Bcl-2 protein expression levels were detected in women with SUI, compared with control subjects. Furthermore, PERK, ATF4, and CHOP mRNA expression levels were significantly higher in women with SUI than in control subjects.

Conclusions

Alterations of ERS markers in SUI suggest that ERS may be involved in the development of SUI in postmenopausal women.

Endoplasmic reticulum stress plays critical role in brain damage after chronic intermittent hypoxia in growing rats

Obstructive sleep apnea hypopnea syndrome (OSAHS) in children is associated with multiple system morbidities. Cognitive dysfunction as a result of central nervous system complication has been reported in children with OSAHS. However, the underlying mechanisms are poorly understood. Endoplasmic reticulum stress (ERS)-related apoptosis plays an important role in various diseases of the central nervous system, but very little is known about the role of ERS in mediating pathophysiological reactions to cognitive dysfunction in OSAHS. Chronic intermittent hypoxia (CIH) exposures, modeling OSAHS, across 2 and 4weeks in growing rats made more reference memory errors, working memory errors and total memory errors in the 8-Arm radial maze task, increased significantly TUNEL positive cells, upregulated the unfolded protein response in the hippocampus and prefrontal cortex as evidenced by increased phosphorylation of PKR-like endoplasmic reticulum kinase, inositol-requiring enzyme l and some downstream products. A selective inhibitor of eukaryotic initiation factor-2a dephosphorylation, salubrinal, prevented C/EBP-homologous protein activation in the hippocampus and prefrontal cortex throughout hypoxia/reoxygenation exposure. Our findings suggest that ERS mediated cell apoptosis may be one of the underlying mechanisms of cognitive dysfunction in OSAHS children. Further, a specific ERS inhibitor Salubrinal should be tested for neuroprotection against CIH-induced injury.

ER stress in human hepatic cells treated with Efavirenz: mitochondria again

BACKGROUND & AIMS

ER stress is associated with a growing number of liver diseases, including drug-induced hepatotoxicity. The non-nucleoside analogue reverse transcriptase inhibitor Efavirenz, a cornerstone of the multidrug strategy employed to treat HIV1 infection, has been related to the development of various adverse events, including metabolic disturbances and hepatic toxicity, the mechanisms of which remain elusive. Recent evidence has pinpointed a specific mitochondrial effect of Efavirenz in human hepatic cells. This study assesses the induction of ER stress by Efavirenz in the same model and the implication of mitochondria in this process.

METHODS

Primary human hepatocytes and Hep3B were treated with clinically relevant concentrations of Efavirenz and parameters of ER stress were studied using standard cell biology techniques.

RESULTS

ER stress markers, including CHOP and GRP78 expression (both protein and mRNA), phosphorylation of eIF2α, and presence of the spliced form of XBP1 were upregulated. Efavirenz also enhanced cytosolic Ca(2+) content and induced morphological changes in the ER suggestive of ER stress. This response was greatly attenuated in cells with altered mitochondrial function (Rho°). The effects of Efavirenz on the ER, and particularly in regard to the mitochondrial involvement, differed from those elicited by a standard pharmacological ER stressor.

CONCLUSIONS

This newly discovered mechanism of cellular insult involving ER stress and UPR response may help comprehend the hepatic toxicity that has been associated with the widespread and life-long use of Efavirenz. In addition, the specificity of the actions of Efavirenz observed expands our knowledge of the mechanisms that trigger ER stress and shed some light on the mitochondria/ER interplay in drug-induced hepatic challenge.

Hyperglycemia induces endoplasmic reticulum stress-dependent CHOP expression in osteoblasts

Diabetic osteoporosis is a metabolic bone disease responsible for global health problems. Hyperglycemia induces osteopenia, increases bone fragility and unbalances the coupling of osteoblasts and osteoclasts. The mechanism is, however, unknown. For the purpose of this study, we hypothesized that hyperglycemia destroys endoplasmic reticulum (ER) homeostasis, activates C/EBP-homologous protein (CHOP) and induces osteoblast apoptosis under diabetic conditions. Diabetic rats were created by injecting streptozotocin (STZ) 65 mg/kg intraperitoneally and their osteoblasts were cultured under high-glucose medium in vitro. The bone mineral density (BMD) and pathological changes of the rats’ femurs were observed. The expression of CHOP in osteoblasts was assayed using immunohistochemistry and western blot analysis. Six weeks after diabetic model establishment, a significant decrease was found in the BMD of the diabetic rat femurs, and the numbers of osteoblasts under cortical bone were also reduced. The expression of the ER stress regulator CHOP in osteoblasts of diabetic rats or high-glucose medium was also elevated (P<0.01). The present results demonstrated that hyperglycemia elevated the expression of CHOP and finally led to osteoporosis. This suggested that elevating the expression of CHOP may play a role in diabetic osteoporosis.

Tunicamycin induces endoplasmic reticulum stress-mediated apoptosis in gastric cancer cell line BGC-823

AIM: To investigate whether tunicamycin (TM) induces endoplasmic reticulum stress-mediated apoptosis in gastric cancer cell line BGC-823.

METHODS: BGC-823 cells were treated with 10 mg/L of TM for 0, 24, 36 and 48 h. After treatment, apoptosis was evaluated by using annexin V-propidium iodide staining, and the expression of C/EBP-homologous protein (CHOP) mRNA and protein was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot, respectively.

RESULTS: The apoptotic rates of BGC-823 cells treated with TM for 0, 24, 36 and 48 h were 0%, 11.8%, 16.3% and 20.4%, respectively, showing a time-dependent increase (P < 0.01). RT-PCR and Western blot results showed that the expression levels of CHOP mRNA and protein were significantly higher in cells treated with TM than in untreated cells. The expression levels of CHOP mRNA and protein increased with the prolongation of treatment duration (both P < 0.01).

CONCLUSION: TM may induce endoplasmic reticulum stress-mediated apoptosis in gastric cancer cell line BGC-823.