Chronic inhibition of endoplasmic reticulum stress and inflammation prevents ischaemia-induced vascular pathology in type II diabetic mice

Tauroursodeoxycholic acid ameliorates renal injury induced by COL4A3 mutation

COL4A3/A4/A5 mutations have been identified as critical causes of Alport syndrome and other genetic chronic kidney diseases. However, the underlying pathogenesis remains unclear, and specific treatments are lacking. Here, we constructed a transgenic Alport syndrome mouse model by generating a mutation (Col4a3 p.G799R) identified previously from one large Alport syndrome family into mice. We observed that the mutation caused a pathological decrease in intracellular and secreted collagen IV α3α4α5 heterotrimers. The mutant collagen IV α3 chains abnormally accumulated in the endoplasmic reticulum and exhibited defective secretion, leading to persistent endoplasmic reticulum stress in vivo and in vitro. RNA-seq analysis revealed that the MyD88/p38 MAPK pathway plays key roles in mediating subsequent inflammation and apoptosis signaling activation. Treatment with tauroursodeoxycholic acid, a chemical chaperone drug that functions as an endoplasmic reticulum stress inhibitor, effectively suppressed endoplasmic reticulum stress, promoted secretion of the α3 chains, and inhibited the activation of the MyD88/p38 MAPK pathway. Tauroursodeoxycholic acid treatment significantly improved kidney function in vivo. These results partly clarified the pathogenesis of kidney injuries associated with Alport syndrome, especially in glomeruli, and suggested that tauroursodeoxycholic acid might be useful for the early clinical treatment of Alport syndrome.

Role of ROS-mediated PERK/ATF4 signaling activation in extracorporeal tube formation injury of human umbilical vein endothelial cells induced by cooking oil fume PM2.5 exposure

Cooking oil fume-derived PM2.5 (COF-PM2.5) is a major source of indoor air contamination in China, which has been demonstrated to be a hazard factor of cardiovascular and cerebrovascular diseases. This study aimed to investigate the role of ROS-mediated PERK/ATF4 signaling activation in COF-PM2.5-inhibited extracorporeal tube formation in human umbilical vein endothelial cells (HUVECs). HUVECs were treated with 100 μg/mL COF-PM2.5 at different times, with or without 100 nM PERK activity inhibitor GSK2606414 (GSK) or 200 μM antioxidant N-acetylcysteine (NAC) pretreatment. Our results showed that COF-PM2.5 exposure can inhibit extracorporeal tube formation and down-regulate VEGFR2 expression in HUVECs. Furthermore, our data indicated that COF-PM2.5 exposure can activate the PERK/ATF4 signaling in HUVECs. Mechanistically, pretreatment with GSK interdicted PERK/ATF4 signaling, thereby reversing COF-PM2.5-downregulated VEGFR2 protein expression in HUVECs. Furthermore, NAC reversed VEGFR2 expression downregulated induced by COF-PM2.5 by inhibiting the upregulation of intracellular ROS levels and PERK/ATF4 signaling in HUVECs. As above, COF-PM2.5 exposure could induce ROS release from HUVECs, which in turn activate the endoplasmic reticulum PERK/ATF4 signaling and inhibit tube formation of HUVECs.

Endoplasmic reticulum stress: a novel targeted approach to repair bone defects by regulating osteogenesis and angiogenesis

Bone regeneration therapy is clinically important, and targeted regulation of endoplasmic reticulum (ER) stress is important in regenerative medicine. The processing of proteins in the ER controls cell fate. The accumulation of misfolded and unfolded proteins occurs in pathological states, triggering ER stress. ER stress restores homeostasis through three main mechanisms, including protein kinase-R-like ER kinase (PERK), inositol-requiring enzyme 1ɑ (IRE1ɑ) and activating transcription factor 6 (ATF6), collectively known as the unfolded protein response (UPR). However, the UPR has both adaptive and apoptotic effects. Modulation of ER stress has therapeutic potential for numerous diseases. Repair of bone defects involves both angiogenesis and bone regeneration. Here, we review the effects of ER stress on osteogenesis and angiogenesis, with emphasis on ER stress under high glucose (HG) and inflammatory conditions, and the use of ER stress inducers or inhibitors to regulate osteogenesis and angiogenesis. In addition, we highlight the ability for exosomes to regulate ER stress. Recent advances in the regulation of ER stress mediated osteogenesis and angiogenesis suggest novel therapeutic options for bone defects.

Interleukin-1β Disruption Protects Male Mice From Heart Failure With Preserved Ejection Fraction Pathogenesis

Background Heart failure with preserved ejection fraction (HFpEF) is a significant unmet need in cardiovascular medicine and remains an untreatable cardiovascular disease. The role and mechanism of interleukin-1β in HFpEF pathogenesis are poorly understood. Methods and Results C57/Bl6J and interleukin-1β-/- male mice were randomly divided into 4 groups. Groups 1 and 2: C57/Bl6J and interleukin-1β-/- mice were fed a regular diet for 4 months and considered controls. Groups 3 and 4: C57/Bl6 and interleukin-1β-/- mice were fed a high-fat diet with N[w]-nitro-l-arginine methyl ester (endothelial nitric oxide synthase inhibitor, 0.5 g/L) in the drinking water for 4 months. We measured body weight, blood pressure, diabetes status, cardiac function/hypertrophy/inflammation, fibrosis, vascular endothelial function, and signaling. C57/Bl6 fed a high-fat diet and N[w]-nitro-l-arginine methyl ester in the drinking water for 4 months developed HFpEF pathogenesis characterized by obesity, diabetes, hypertension, cardiac hypertrophy, lung edema, low running performance, macrovascular and microvascular endothelial dysfunction, and diastolic cardiac dysfunction but no change in cardiac ejection fraction compared with control mice. Interestingly, the genetic disruption of interleukin-1β protected mice from HFpEF pathogenesis through the modulation of the inflammation and endoplasmic reticulum stress mechanisms. Conclusions Our data suggest that interleukin-1β is a critical driver in the development of HFpEF pathogenesis, likely through regulating inflammation and endoplasmic reticulum stress pathways. Our findings provide a potential therapeutic target for HFpEF treatment.

Disrupting Interleukin 12 Improves Microvascular Endothelial Function in Type 2 Diabetes Through ER Stress CHOP and Oxidative Stress Mechanisms

PURPOSE

Vascular endothelial dysfunction is well established in type 2 diabetes. Interleukin-12 (IL-12) and endoplasmic reticulum (ER) stress are up-regulated in type 2 diabetic patients and animal models of type 2 diabetes. However, the role and underlying mechanisms of IL-12 and the ER stress CHOP in endothelial dysfunction are not fully understood.

METHODS

We generated double knockout mice between db^-/db^- and p40IL-12^-/- mice (db^-/db^{-p40-IL-12-/-}) and endoplasmic (ER) stress-CHOP^-/- mice (db^-/db^-CHOP-/-). We performed a glucose tolerance test (GTT) to determine the effect of IL-12 and ER stress CHOP on glucose metabolism. We assessed the endothelial function and determined the phosphorylation level of eNOS, Akt, AMPK, and the expression of ER stress (CHOP, BIP), and oxidative stress (Nox2 and Nox4 and NADPH oxidase activity).

RESULTS

The results showed that GTT was improved in db-/db^{-p40-IL-12-/-} and db^-/db^-CHOP-/- suggesting IL-12 and CHOP as parts of a mechanism involved in the development of type 2 diabetes. The microvascular endothelial dysfunction in db^-/db^- mouse is associated with decreased phosphorylated eNOS, Akt, AMPK, and increased CHOP, BIP, Nox2, and Nox4 expressions. Interestingly, disrupting IL-12 and ER stress CHOP in db^-/db^- mice significantly improved endothelial function, increased survival markers expression and decreased ER and oxidative stress.

CONCLUSION

Using a genetic approach, these findings provide evidence that IL-12 and ER stress CHOP play a significant role in microvascular endothelial dysfunction in type 2 diabetes.

Ischemic brain injury in diabetes and endoplasmic reticulum stress

Diabetes is a widespread disease characterized by high blood glucose levels due to abnormal insulin activity, production, or both. Chronic diabetes causes many secondary complications including cardiovascular disease: a life-threatening complication. Cerebral ischemia-related mortality, morbidity, and the extent of brain injury are high in diabetes. However, the mechanism of increase in ischemic brain injury during diabetes is not well understood. Multiple mechanisms mediate diabetic hyperglycemia and hypoglycemia-induced increase in ischemic brain injury. Endoplasmic reticulum (ER) stress mediates both brain injury as well as brain protection after ischemia-reperfusion injury. The pathways of ER stress are modulated during diabetes. Free radical generation and mitochondrial dysfunction, two of the prominent mechanisms that mediate diabetic increase in ischemic brain injury, are known to stimulate the pathways of ER stress. Increased ischemic brain injury in diabetes is accompanied by a further increase in the activation of ER stress. As there are many metabolic changes associated with diabetes, differential activation of the pathways of ER stress may mediate pronounced ischemic brain injury in subjects suffering from diabetes. We presently discuss the literature on the significance of ER stress in mediating increased ischemia-reperfusion injury in diabetes.

Hypercholesterolemia Impairs Clearance of Neutrophil Extracellular Traps and Promotes Inflammation and Atherosclerotic Plaque Progression

Objective: Hypercholesterolemia-induced NETosis and accumulation of neutrophil extracellular traps (NETs) in the atherosclerotic lesion exacerbates inflammation and is causally implicated in plaque progression. We investigated whether hypercholesterolemia additionally impairs the clearance of NETs mediated by endonucleases such as DNase1 and DNase1L3 and its implication in advanced atherosclerotic plaque progression. Approach and Results: Using a mouse model, we demonstrate that an experimental increase in the systemic level of NETs leads to a rapid increase in serum DNase activity, which is critical for the prompt clearance of NETs and achieving inflammation resolution. Importantly, hypercholesterolemic mice demonstrate an impairment in this critical NET-induced DNase response with consequent delay in the clearance of NETs and defective inflammation resolution. Administration of tauroursodeoxycholic acid, a chemical chaperone that relieves endoplasmic reticulum stress, rescued the hypercholesterolemia-induced impairment in the NET-induced DNase response suggesting a causal role for endoplasmic reticulum stress in this phenomenon. Correction of the defective DNase response with exogenous supplementation of DNase1 in Apoe-/- mice with advanced atherosclerosis resulted in a decrease in plaque NET content and significant plaque remodeling with decreased area of plaque necrosis and increased collagen content. From a translational standpoint, we demonstrate that humans with hypercholesterolemia have elevated systemic extracellular DNA levels and decreased plasma DNase activity. Conclusions: These data suggest that hypercholesterolemia impairs the NET-induced DNase response resulting in defective clearance and accumulation of NETs in the atherosclerotic plaque. Therefore, strategies aimed at rescuing this defect could be of potential therapeutic benefit in promoting inflammation resolution and atherosclerotic plaque stabilization.

Roles and Therapeutic Implications of Endoplasmic Reticulum Stress and Oxidative Stress in Cardiovascular Diseases

In different pathological states that cause endoplasmic reticulum (ER) calcium depletion, altered glycosylation, nutrient deprivation, oxidative stress, DNA damage or energy perturbation/fluctuations, the protein folding process is disrupted and the ER becomes stressed. Studies in the past decade have demonstrated that ER stress is closely associated with pathogenesis of obesity, insulin resistance and type 2 diabetes. Excess nutrients and inflammatory cytokines associated with metabolic diseases can trigger or worsen ER stress. ER stress plays a critical role in the induction of endothelial dysfunction and atherosclerosis. Signaling pathways including AMP-activated protein kinase and peroxisome proliferator-activated receptor have been identified to regulate ER stress, whilst ER stress contributes to the imbalanced production between nitric oxide (NO) and reactive oxygen species (ROS) causing oxidative stress. Several drugs or herbs have been proved to protect against cardiovascular diseases (CVD) through inhibition of ER stress and oxidative stress. The present article reviews the involvement of ER stress and oxidative stress in cardiovascular dysfunction and the potential therapeutic implications.

Heparan sulfate proteoglycans in beta cells provide a critical link between endoplasmic reticulum stress, oxidative stress and type 2 diabetes

Heparan sulfate proteoglycans (HSPGs) consist of a core protein with side chains of the glycosaminoglycan heparan sulfate (HS). We have previously identified (i) the HSPGs syndecan-1 (SDC1), and collagen type XVIII (COL18) inside mouse and human islet beta cells, and (ii) a critical role for HS in beta cell survival and protection from reactive oxygen species (ROS). The objective of this study was to investigate whether endoplasmic reticulum (ER) stress contributes to oxidative stress and type 2 diabetes (T2D) by depleting beta cell HSPGs/HS. A rapid loss of intra-islet/beta cell HSPGs, HS and heparanase (HPSE, an HS-degrading enzyme) accompanied upregulation of islet ER stress gene expression in both young T2D-prone db/db and Akita Ins2^WT/C96Y mice. In MIN6 beta cells, HSPGs, HS and HPSE were reduced following treatment with pharmacological inducers of ER stress (thapsigargin or tunicamycin). Treatment of young db/db mice with Tauroursodeoxycholic acid (TUDCA), a chemical protein folding chaperone that relieves ER stress, improved glycemic control and increased intra-islet HSPG/HS. In vitro, HS replacement with heparin (a highly sulfated HS analogue) significantly increased the survival of wild-type and db/db beta cells and restored their resistance to hydrogen peroxide-induced death. We conclude that ER stress inhibits the synthesis/maturation of HSPG core proteins which are essential for HS assembly, thereby exacerbating oxidative stress and promoting beta cell failure. Diminished intracellular HSPGs/HS represent a previously unrecognized critical link bridging ER stress, oxidative stress and beta cell failure in T2D.

Endoplasmic Reticulum Stress Provocation by Different Nanoparticles: An Innovative Approach to Manage the Cancer and Other Common Diseases

A proper execution of basic cellular functions requires well-controlled homeostasis including correct protein folding. Endoplasmic reticulum (ER) implements such functions by protein reshaping and post-translational modifications. Different insults imposed on cells could lead to ER stress-mediated signaling pathways, collectively called the unfolded protein response (UPR). ER stress is also closely linked with oxidative stress, which is a common feature of diseases such as stroke, neurodegeneration, inflammation, metabolic diseases, and cancer. The level of ER stress is higher in cancer cells, indicating that such cells are already struggling to survive. Prolonged ER stress in cancer cells is like an Achilles' heel, if aggravated by different agents including nanoparticles (NPs) may be exhausted off the pro-survival features and can be easily subjected to proapoptotic mode. Different types of NPs including silver, gold, silica, graphene, etc. have been used to augment the cytotoxicity by promoting ER stress-mediated cell death. The diverse physico-chemical properties of NPs play a great role in their biomedical applications. Some special NPs have been effectively used to address different types of cancers as these particles can be used as both toxicological or therapeutic agents. Several types of NPs, and anticancer drug nano-formulations have been engineered to target tumor cells to enhance their ER stress to promote their death. Therefore, mitigating ER stress in cancer cells in favor of cell death by ER-specific NPs is extremely important in future therapeutics and understanding the underlying mechanism of how cancer cells can respond to NP induced ER stress is a good choice for the development of novel therapeutics. Thus, in depth focus on NP-mediated ER stress will be helpful to boost up developing novel pro-drug candidates for triggering pro-death pathways in different cancers.

Role of smooth muscle cells in Cardiovascular Disease

Normally, smooth muscle cells (SMCs) are localized in the tunica media of the vasculature, where they take responsibility for vascular contraction and extracellular matrix (ECM) generation. SMCs also play a significant role in obedience and elastic rebound of the artery in response to the haemodynamic condition. However, under pathological or stressed conditions, phenotype switching from contractile to synthetic state or other cell types will occur in SMCs to positively or negatively contribute to disease progression. Various studies demonstrated that functional changes of SMCs are implicated in several cardiovascular diseases. In this review, we present the function of vascular SMCs (VSMCs) and the involved molecular mechanisms about phenotype switching, and summarize the roles of SMCs in atherosclerosis, hypertension, arterial aneurysms and myocardial infarction, hoping to obtain potential therapeutic targets against cardiovascular disease in the clinical practices.

Tauroursodeoxycholic acid (TUDCA) abolishes chronic high salt-induced renal injury and inflammation

AIM

Chronic high salt intake exaggerates renal injury and inflammation, especially with the loss of functional ET_B receptors. Tauroursodeoxycholic acid (TUDCA) is a chemical chaperone and bile salt that is approved for the treatment of hepatic diseases. Our aim was to determine whether TUDCA is reno-protective in a model of ET_B receptor deficiency with chronic high salt-induced renal injury and inflammation.

METHODS

ET_B -deficient and transgenic control rats were placed on normal (0.8% NaCl) or high salt (8% NaCl) diet for 3 weeks, receiving TUDCA (400 mg/kg/d; ip) or vehicle. Histological and biochemical markers of kidney injury, renal cell death and renal inflammation were assessed.

RESULTS

In ET_B -deficient rats, high salt diet significantly increased glomerular and proximal tubular histological injury, proteinuria, albuminuria, excretion of tubular injury markers KIM-1 and NGAL, renal cortical cell death and renal CD4⁺ T cell numbers. TUDCA treatment increased proximal tubule megalin expression as well as prevented high salt diet-induced glomerular and tubular damage in ET_B -deficient rats, as indicated by reduced kidney injury markers, decreased glomerular permeability and proximal tubule brush border restoration, as well as reduced renal inflammation. However, TUDCA had no significant effect on blood pressure.

CONCLUSIONS

TUDCA protects against the development of glomerular and proximal tubular damage, decreases renal cell death and inflammation in the renal cortex in rats with ET_B receptor dysfunction on a chronic high salt diet. These results highlight the potential use of TUDCA as a preventive tool against chronic high salt induced renal damage.

Crosstalk Between Oxidative Stress and Endoplasmic Reticulum (ER) Stress in Endothelial Dysfunction and Aberrant Angiogenesis Associated With Diabetes: A Focus on the Protective Roles of Heme Oxygenase (HO)-1

Type-2 diabetes prevalence is continuing to rise worldwide due to physical inactivity and obesity epidemic. Diabetes and fluctuations of blood sugar are related to multiple micro- and macrovascular complications, that are attributed to oxidative stress, endoplasmic reticulum (ER) activation and inflammatory processes, which lead to endothelial dysfunction characterized, among other features, by reduced availability of nitric oxide (NO) and aberrant angiogenic capacity. Several enzymatic anti-oxidant and anti-inflammatory agents have been found to play protective roles against oxidative stress and its downstream signaling pathways. Of particular interest, heme oxygenase (HO) isoforms, specifically HO-1, have attracted much attention as major cytoprotective players in conditions associated with inflammation and oxidative stress. HO operates as a key rate-limiting enzyme in the process of degradation of the iron-containing molecule, heme, yielding the following byproducts: carbon monoxide (CO), iron, and biliverdin. Because HO-1 induction was linked to pro-oxidant states, it has been regarded as a marker of oxidative stress; however, accumulating evidence has established multiple cytoprotective roles of the enzyme in metabolic and cardiovascular disorders. The cytoprotective effects of HO-1 depend on several cellular mechanisms including the generation of bilirubin, an anti-oxidant molecule, from the degradation of heme; the induction of ferritin, a strong chelator of free iron; and the release of CO, that displays multiple anti-inflammatory and anti-apoptotic actions. The current review article describes the major molecular mechanisms contributing to endothelial dysfunction and altered angiogenesis in diabetes with a special focus on the interplay between oxidative stress and ER stress response. The review summarizes the key cytoprotective roles of HO-1 against hyperglycemia-induced endothelial dysfunction and aberrant angiogenesis and discusses the major underlying cellular mechanisms associated with its protective effects.

Critical role of endoplasmic reticulum stress in chronic endothelial activation-induced visual deficits in tie2-tumor necrosis factor mice

Diabetic retinopathy (DR) is the leading cause of vision loss among working-age adults. The interplay between hyperglycemia and endothelial activation in inducing endoplasmic reticulum (ER) stress pathways and visual deficits in DR is not fully understood. To address this, we used a mouse model of chronic vascular activation using endothelial-specific tumor necrosis factor-α (TNF-α)-expressing (tie2-TNF) mice to induce diabetes with streptozotocin. At 4 weeks post streptozotocin, a significant 2-fold to 10-fold increase in retinal neurovascular inflammatory gene transcript response in tie2-TNF mice was further increased in diabetic tie2-TNF mice. A decrease in visual acuity and scotopic b-wave amplitude in tie2-TNF mice was further accentuated in diabetic tie2-TNF mice and these changes correlated with a multi-fold increase in retinal ER stress markers and a reduction in adherens junctions. Cultured retinal endothelial cells showed a significant decrease in trans-endothelial resistance as well as VE-cadherin expression under TNF-α and high glucose stress. These changes were partly rescued by tauroursodeoxycholic acid, a potent ER stress inhibitor. Taken together, constant endothelial activation induced by TNF-α further exacerbated by hyperglycemia results in activation of ER stress and chronic proinflammation in a feed forward loop ultimately resulting in endothelial junction protein alterations leading to visual deficits in the retina. Inhibition of ER stress and endothelial activation may prove to be a novel therapeutic target in DR.

Essential role for smooth muscle cell stromal interaction molecule-1 in myocardial infarction

OBJECTIVES

Stromal interacting molecule-1 (STIM1) plays a role in coordinating calcium signaling in different cell types. The increase or deletion of STIM1 expression in cardiomyocyte causes cardiac complication. Moreover, the deletion of STIM1 in endothelial cell causes vascular endothelial dysfunction. However, the disruption of STIM1 in smooth muscle cells (SMC) has no effect on endothelial function but protects vascular function when mice are infused with angiotensin-II. Nevertheless, the role of SMC-STIM1 in acute and chronic myocardial infarction (MI) induced by acute ischemia-reperfusion injury and permanent coronary artery occlusion is unknown.

METHODS AND RESULTS

Stim1 were generated and crossed into the SM22α-Cre backgrounds. SM22α-Cre causes deletion of STIM1 floxed genes in adult SMC (Stim1). Control and Stim1 mice were subjected to acute ischemia-reperfusion injury. Hearts were then harvested and incubated with triphenyltetrazolium chloride to determine the infarct size. In control mice which are subjected to ischemia-reperfusion, the heart developed a significant infarct associated with an increase in STIM1 expression. Interestingly, the infarct size was substantially reduced in Stim1 mice. The protection in Stim1 mice against ischemia-reperfusion injury involves the modulation of endoplasmic reticulum stress, apoptosis, oxidative stress, protein kinase B, and mitogen-activated protein (MAP) kinase (ERK1/2 and p38) signaling, and inflammation. Furthermore, in another model of chronic MI induced by permanent coronary artery occlusion, SMC-STIM1 disruption significantly reduced myocardial infarct size and improved cardiac function.

CONCLUSION

Our results provide new evidence that SMC-STIM1 disruption is a novel mechanism that protects the heart from MI through reduction of endoplasmic reticulum stress, oxidative stress, MAP-Kinase, apoptosis, and inflammation.

Essential role for EGFR tyrosine kinase and ER stress in myocardial infarction in type 2 diabetes

We previously reported that EGFR tyrosine kinase (EGFRtk) activity and endoplasmic reticulum (ER) stress are enhanced in type 2 diabetic (T2D) mice and cause vascular dysfunction. In the present study, we determined the in vivo contribution of EGFRtk and ER stress in acute myocardial infarction induced by acute ischemia (40 min)-reperfusion (24 h) (I/R) injury in T2D (db^-/db^-) mice. We treated db^-/db^- mice with EGFRtk inhibitor (AG1478, 10 mg/kg/day) for 2 weeks. Mice were then subjected to myocardial I/R injury. The db^-/db^- mice developed a significant infarct after I/R injury. The inhibition of EGFRtk significantly reduced the infarct size and ER stress induction. We also determined that the inhibition of ER stress (tauroursodeoxycholic acid, TUDCA, 150 mg/kg per day) in db^-/db^- significantly decrease the infarct size indicating that ER stress is a downstream mechanism to EGFRtk. Moreover, AG1478 and TUDCA reduced myocardium p38 and ERK1/2 MAP-kinases activity, and increased the activity of the pro-survival signaling cascade Akt. Additionally, the inhibition of EGFRtk and ER stress reduced cell apoptosis and the inflammation as indicated by the reduction in macrophages and neutrophil infiltration. We determined for the first time that the inhibition of EGFRtk protects T2D heart against I/R injury through ER stress-dependent mechanism. The cardioprotective effect of EGFRtk and ER stress inhibition involves the activation of survival pathway, and inhibition of apoptosis, and inflammation. Thus, targeting EGFRtk and ER stress has the potential for therapy to overcome myocardial infarction in T2D.

Essential Role of IL-12 in Angiogenesis in Type 2 Diabetes

Recently, IL-12 emerged as a critical player in type 2 diabetes complications. We previously reported that ischemia-induced angiogenesis is compromised in type 2 diabetic mice. In this study, we determined that IL-12 disruption rescued angiogenesis and arteriogenesis in type 2 diabetic mice. To induce type 2 diabetes, wild-type (WT), p40IL-12^-/- (p40^-/-), and p35IL-12^-/- (p35^-/-) mice were fed a high-fat diet (HFD) for 12 weeks. Body weight, glucose test tolerance, and insulin test tolerance were assessed. After 12 weeks of an HFD, the femoral artery was ligated and blood flow recovery was measured every week for 4 weeks. WT, p40^-/-, and p35^-/- mice fed an HFD become obese after 12 weeks and exhibit glucose intolerance and insulin resistance. Blood flow recovery was fully restored in 2 to 3 weeks after femoral artery ligation in all groups of mice fed a normal diet. However, after 12 weeks of an HFD, blood flow recovery was compromised in WT mice, whereas it was fully recovered in p40^-/- and p35^-/- mice. The mechanism of blood flow recovery involves an increase in capillary/arteriole density, endothelial nitric oxide synthase/Akt/vascular endothelial growth factor receptor 2 signaling, and a reduction in oxidative stress and inflammation. The disruption of IL-12 promotes angiogenesis and increases blood flow recovery in obese type 2 diabetic mice by an endothelial nitric oxide synthase/Akt/vascular endothelial growth factor receptor 2/oxidative stress-inflammation-dependent mechanism.

IL-1β Inhibition in Cardiovascular Complications Associated to Diabetes Mellitus

Diabetes mellitus (DM) is a chronic disease that affects nowadays millions of people worldwide. In adults, type 2 diabetes mellitus (T2DM) accounts for the majority of all diagnosed cases of diabetes. The course of the T2DM is characterized by insulin resistance and a progressive loss of β-cell mass. DM is associated with a number of related complications, among which cardiovascular complications and atherosclerosis are the main cause of morbidity and mortality in patients suffering from the disease. DM is acknowledged as a low-grade chronic inflammatory state characterized by the over-secretion of pro-inflammatory cytokines, including interleukin (IL)-1β, which reinforce inflammatory signals thus contributing to the development of complications. In this context, the pharmacological approaches to treat diabetes should not only correct hyperglycaemia, but also attenuate inflammation and prevent the development of metabolic and cardiovascular complications. Over the last years, novel biological drugs have been developed to antagonize the pathophysiological actions of IL-1β. The drugs currently used in clinical practice are anakinra, a recombinant form of the naturally occurring IL-1 receptor antagonist, the soluble decoy receptor rilonacept and the monoclonal antibodies canakinumab and gevokizumab. This review will summarize the main experimental and clinical findings obtained with pharmacological IL-1β inhibitors in the context of the cardiovascular complications of DM, and discuss the perspectives of IL-1β inhibitors as novel therapeutic tools for treating these patients.

Increased monocyte-derived reactive oxygen species in type 2 diabetes: role of endoplasmic reticulum stress

NEW FINDINGS

What is the central question of this study? Patients with type 2 diabetes exhibit increased oxidative stress in peripheral blood mononuclear cells, including monocytes; however, the mechanisms remain unknown. What is the main finding and its importance? The main finding of this study is that factors contained within the plasma of patients with type 2 diabetes can contribute to increased oxidative stress in monocytes, making them more adherent to endothelial cells. We show that these effects are largely mediated by the interaction between endoplasmic reticulum stress and NADPH oxidase activity. Recent evidence suggests that exposure of human monocytes to glucolipotoxic media to mimic the composition of plasma of patients with type 2 diabetes (T2D) results in the induction of endoplasmic reticulum (ER) stress markers and formation of reactive oxygen species (ROS). The extent to which these findings translate to patients with T2D remains unclear. Thus, we first measured ROS (dihydroethidium fluorescence) in peripheral blood mononuclear cells (PBMCs) from whole blood of T2D patients (n = 8) and compared the values with age-matched healthy control subjects (n = 8). The T2D patients exhibited greater basal intracellular ROS (mean ± SD, +3.4 ± 1.4-fold; P < 0.05) compared with control subjects. Next, the increase in ROS in PBMCs isolated from T2D patients was partly recapitulated in cultured human monocytes (THP-1 cells) exposed to plasma from T2D patients for 36 h (+1.3 ± 0.08-fold versus plasma from control subjects; P < 0.05). In addition, we found that increased ROS formation in THP-1 cells treated with T2D plasma was NADPH oxidase derived and led to increased endothelial cell adhesion (+1.8 ± 0.5-fold; P < 0.05) and lipid uptake (+1.3 ± 0.3-fold; P < 0.05). Notably, we found that T2D plasma-induced monocyte ROS and downstream functional effects were abolished by treating cells with tauroursodeoxycholic acid, a chemical chaperone known to inhibit ER stress. Collectively, these data indicate that monocyte ROS production with T2D can be attributed, in part, to signals from the circulating environment. Furthermore, an interplay between ER stress and NADPH oxidase activity contributes to ROS production and may be a mechanism mediating endothelial cell adhesion and foam cell formation in T2D.

Heme oxygenase (HO)-1 induction prevents Endoplasmic Reticulum stress-mediated endothelial cell death and impaired angiogenic capacity

Most of diabetic cardiovascular complications are attributed to endothelial dysfunction and impaired angiogenesis. Endoplasmic Reticulum (ER) and oxidative stresses were shown to play a pivotal role in the development of endothelial dysfunction in diabetes. Hemeoxygenase-1 (HO-1) was shown to protect against oxidative stress in diabetes; however, its role in alleviating ER stress-induced endothelial dysfunction remains not fully elucidated. We aim here to test the protective role of HO-1 against high glucose-mediated ER stress and endothelial dysfunction and understand the underlying mechanisms with special emphasis on oxidative stress, inflammation and cell death. Human Umbilical Vein Endothelial Cells (HUVECs) were grown in either physiological or intermittent high concentrations of glucose for 5days in the presence or absence of Cobalt (III) Protoporphyrin IX chloride (CoPP, HO-1 inducer) or 4-Phenyl Butyric Acid (PBA, ER stress inhibitor). Using an integrated cellular and molecular approach, we then assessed ER stress and inflammatory responses, in addition to apoptosis and angiogenic capacity in these cells. Our results show that HO-1 induction prevented high glucose-mediated increase of mRNA and protein expression of key ER stress markers. Cells incubated with high glucose exhibited high levels of oxidative stress, activation of major inflammatory and apoptotic responses [nuclear factor (NF)-κB and c-Jun N-terminal kinase (JNK)] and increased rate of apoptosis; however, cells pre-treated with CoPP or PBA were fully protected. In addition, high glucose enhanced caspases 3 and 7 cleavage and activity and augmented cleaved poly ADP ribose polymerase (PARP) expression whereas HO-1 induction prevented these effects. Finally, HO-1 induction and ER stress inhibition prevented high glucose-induced reduction in NO release and impaired the angiogenic capacity of HUVECs, and enhanced vascular endothelial growth factor (VEGF)-A expression. Altogether, we show here the critical role of ER stress-mediated cell death in diabetes-induced endothelial dysfunction and impaired angiogenesis and underscore the role of HO-1 induction as a key therapeutic modulator for ER stress response in ischemic disorders and diabetes. Our results also highlight the complex interplay between ER stress response and oxidative stress.

Inhibition of endoplasmic reticulum stress improves coronary artery function in the spontaneously hypertensive rats

Endoplasmic reticulum (ER) stress has been shown to play a critical role in the pathogenesis of cardiovascular complications. However, the role and mechanisms of ER stress in hypertension remain unclear. Thus, we hypothesized that enhanced ER stress contributes to the maintenance of hypertension in spontaneously hypertensive rats (SHRs). Sixteen-week old male SHRs and Wistar Kyoto Rats (WKYs) were used in this study. The SHRs were treated with ER stress inhibitor (Tauroursodeoxycholic acid; TUDCA, 100 mg/kg/day) for two weeks. There was a decrease in systolic blood pressure in SHR treated with TUDCA. The pressure-induced myogenic tone was significantly increased, whereas endothelium-dependent relaxation was significantly attenuated in SHR compared with WHY. Interestingly, treatment of ER stress inhibitor normalized myogenic responses and endothelium-dependent relaxation in SHR. These data were associated with an increase in expression or phosphorylation of ER stress markers (Bip, ATF6, CHOP, IRE1, XBP1, PERK, and eIF2α) in SHRs, which were reduced by TUDCA treatment. Furthermore, phosphorylation of MLC20 was increased in SHRs, which was reduced by the treatment of TUDCA. Therefore, our results suggest that ER stress could be a potential target for hypertension.

Administration of tauroursodeoxycholic acid prevents endothelial dysfunction caused by an oral glucose load

Postprandial hyperglycaemia leads to a transient impairment in endothelial function; however, the mechanisms remain largely unknown. Previous work in cell culture models demonstrate that high glucose results in endoplasmic reticulum (ER) stress and, in animal studies, ER stress has been implicated as a cause of endothelial dysfunction. In the present study, we tested the hypothesis that acute oral administration of tauroursodeoxycholic acid (TUDCA, 1500 mg), a chemical chaperone known to alleviate ER stress, would prevent hyperglycaemia-induced endothelial dysfunction. In 12 young healthy subjects (seven men, five women), brachial artery flow-mediated dilation (FMD) was assessed at baseline, and at 60 and 120 min after an oral glucose challenge. Subjects were tested on two separate visits in a single-blind randomized cross-over design: after oral ingestion of TUDCA or placebo capsules. FMD was reduced from baseline during hyperglycaemia under the placebo condition (-32% at 60 min and -28% at 120 min post oral glucose load; P<0.05 from baseline) but not under the TUDCA condition (-4% at 60 min and +0.3% at 120 min post oral glucose load; P>0.05 from baseline). Postprandial plasma glucose and insulin were not altered by TUDCA ingestion. Plasma oxidative stress markers 3-nitrotyrosine and thiobarbituric acid reactive substance (TBARS) remained unaltered throughout the oral glucose challenge in both conditions. These results suggest that hyperglycaemia-induced endothelial dysfunction can be mitigated by oral administration of TUDCA, thus supporting the hypothesis that ER stress may contribute to endothelial dysfunction during postprandial hyperglycaemia.

Angiopoietin-1 attenuates angiotensin II-induced ER stress in glomerular endothelial cells via a Tie2 receptor/ERK1/2-p38 MAPK-dependent mechanism

Research has indicated that endoplasmic reticulum (ER) stress in endothelial cells affects vascular pathologies and induces cellular dysfunction and apoptosis. Angiopoietin1 (Angpt1) has been shown to have therapeutic potential in some vascular diseases, including chronic kidney disease. This study showed that Angpt1 is a powerful factor that attenuated ER stress-induced cellular dysfunction and apoptosis in glomerular endothelial cells (GEnCs). Furthermore, Angpt1 significantly decreased the angiotensin II (Ang II)-induced expression of the ER stress response proteins GRP78, GRP94, p-PERK and CHOP. These results suggest that the Angpt1-mediated cellular protection may occur downstream of the ER stress response. In addition, both specific inhibitors and siRNAs for Tie2 reversed these changes, implying the importance of Tie2 receptor activation in the signalling pathways that prevent ER stress. The protective effects of Angpt1 are related to the activation of two downstream signalling pathways, ERK1/2 and p38 MAPK. The inhibition of these pathways with specific inhibitors, PD98059 and SB203580, respectively, partially increased the expression of chaperones that assist in folding proteins in the ER and reduce the protective effects of Angpt1. In conclusion, Angpt1 attenuated ER stress-induced cellular dysfunction and apoptosis via the Tie2 receptor/ERK1/2-p38 MAPK pathways in GEnCs. This study may provide insights into a novel underlying mechanism and a strategy for alleviating ER stress-induced injury.

Dialogue between endoplasmic reticulum and mitochondria as a key actor of vascular dysfunction associated to metabolic disorders

Metabolic syndrome due to its association with increased risk of cardiovascular diseases and cardiac mortality, comprises a cluster of metabolic abnormalities such as central obesity, hyperglycemia, dyslipidemia, and hypertension. Recent studies have shown that metabolic syndrome patients exhibit impaired nitric oxide-mediated vasodilatation leading to endothelial dysfunction in addition to insulin resistance. Interestingly, development and maintenance of the unfolded protein response of the endoplasmic reticulum stress revealed a surprisingly direct link with metabolic syndrome and endothelial dysfunction. On the other hand, in metabolic disorders, interaction between endoplasmic reticulum and mitochondria is mandatory for the generation of mitochondrial oxidative stress and perturbation of mitochondrial function accounting, at least in part, for vascular dysfunction. Herein, we review the impact of the dialogue between endoplasmic reticulum and mitochondria in modulating the cellular signals governing vascular alterations associated to metabolic disorders.

Effect of a chemical chaperone, tauroursodeoxycholic acid, on HDM-induced allergic airway disease

Endoplasmic reticulum (ER) stress-induced unfolded protein response plays a critical role in inflammatory diseases, including allergic airway disease. However, the benefits of inhibiting ER stress in the treatment of allergic airway disease are not well known. Herein, we tested the therapeutic potential of a chemical chaperone, tauroursodeoxycholic acid (TUDCA), in combating allergic asthma, using a mouse model of house dust mite (HDM)-induced allergic airway disease. TUDCA was administered during the HDM-challenge phase (preventive regimen), after the HDM-challenge phase (therapeutic regimen), or therapeutically during a subsequent HDM rechallenge (rechallenge regimen). In the preventive regimen, TUDCA significantly decreased HDM-induced inflammation, markers of ER stress, airway hyperresponsiveness (AHR), and fibrosis. Similarly, in the therapeutic regimen, TUDCA administration efficiently decreased HDM-induced airway inflammation, mucus metaplasia, ER stress markers, and AHR, but not airway remodeling. Interestingly, TUDCA administered therapeutically in the HDM rechallenge regimen markedly attenuated HDM-induced airway inflammation, mucus metaplasia, ER stress markers, methacholine-induced AHR, and airway fibrotic remodeling. These results indicate that the inhibition of ER stress in the lungs through the administration of chemical chaperones could be a valuable strategy in the treatment of allergic airway diseases.

Targeting Imbalance between IL-1β and IL-1 Receptor Antagonist Ameliorates Delayed Epithelium Wound Healing in Diabetic Mouse Corneas

Patients with diabetes mellitus often develop corneal complications and delayed wound healing. How diabetes might alter acute inflammatory responses to tissue injury, leading to delayed wound healing, remains mostly elusive. Using a streptozotocin-induced type I diabetes mellitus mice and corneal epithelium-debridement wound model, we discovered that although wounding induced marked expression of IL-1β and the secreted form of IL-1 receptor antagonist (sIL-1Ra), diabetes suppressed the expressions of sIL-1Ra but not IL-1β in healing epithelia and both in whole cornea. In normoglycemic mice, IL-1β or sIL-1Ra blockade delayed wound healing and influenced each other's expression. In diabetic mice, in addition to delayed reepithelization, diabetes weakened phosphatidylinositol 3-kinase-Akt signaling, caused cell apoptosis, diminished cell proliferation, suppressed neutrophil and natural killer cell infiltrations, and impaired sensory nerve reinnervation in healing mouse corneas. Local administration of recombinant IL-1Ra partially, but significantly, reversed these pathological changes in the diabetic corneas. CXCL10 was a downstream chemokine of IL-1β-IL-1Ra, and exogenous CXCL10 alleviated delayed wound healing in the diabetic, but attenuated it in the normal corneas. In conclusion, the suppressed early innate/inflammatory responses instigated by the imbalance between IL-1β and IL-1Ra is an underlying cause for delayed wound healing in the diabetic corneas. Local application of IL-1Ra accelerates reepithelialization and may be used to treat chronic corneal and potential skin wounds of diabetic patients.

Therapeutic window of globular adiponectin against cerebral ischemia in diabetic mice: the role of dynamic alteration of adiponectin/adiponectin receptor expression

Recent studies have demonstrated that adiponectin (APN) attenuates cerebral ischemic/reperfusion via globular adiponectin (gAD). However, the therapeutic role of gAD in cerebral ischemic injury in type 1 diabetes mellitus (T1DM) remains unclear. Our results showed that gAD improved neurological scores and reduced the infarct volumes in the 8-week T1DM (T1DM-8W) mice, but not in the 2-week T1DM (T1DM-2W) mice. Moreover, the ischemic penumbra APN levels increased and peaked in T1DM-2W mice, and reduced to normal in T1DM-8W mice, while the APN receptor 1 (AdipoR1) expression change was the opposite. Administration of rosiglitazone in T1DM-2W mice up-regulated the expression of AdipoR1 and restored the neuroprotection of gAD, while intracerebroventricular injection of AdipoR1 small interfering RNA (siRNA) in T1DM-8W mice reversed it. Furthermore, the expression of p-PERK, p-IRE1 and GRP78 were increased whereas the expressions of CHOP and cleaved caspase-12 as well as the number of apoptotic neurons were decreased after gAD treatment in T1DM-8W mice. These beneficial effects of gAD were reversed by pretreatment with AdipoR1 siRNA. These results demonstrated a dynamic dysfunction of APN/AdipoR1 accompanying T1DM progression. Interventions bolstering AdipoR1 expression during early stages and gAD supplementation during advanced stages may potentially reduce the cerebral ischemic injury in diabetic patients.

The interleukin-1 receptor antagonist anakinra improves endothelial dysfunction in streptozotocin-induced diabetic rats

Background

Endothelial dysfunction is a crucial early phenomenon in vascular diseases linked to diabetes mellitus and associated to enhanced oxidative stress. There is increasing evidence about the role for pro-inflammatory cytokines, like interleukin-1β (IL-1β), in developing diabetic vasculopathy. We aimed to determine the possible involvement of this cytokine in the development of diabetic endothelial dysfunction, analysing whether anakinra, an antagonist of IL-1 receptors, could reduce this endothelial alteration by interfering with pro-oxidant and pro-inflammatory pathways into the vascular wall.

Results

In control and two weeks evolution streptozotocin-induced diabetic rats, either untreated or receiving anakinra, vascular reactivity and NADPH oxidase activity were measured, respectively, in isolated rings and homogenates from mesenteric microvessels, while nuclear factor (NF)-κB activation was determined in aortas. Plasma levels of IL-1β and tumor necrosis factor (TNF)-α were measured by ELISA. In isolated mesenteric microvessels from control rats, two hours incubation with IL-1β (1 to 10 ng/mL) produced a concentration-dependent impairment of endothelium-dependent relaxations, which were mediated by enhanced NADPH oxidase activity via IL-1 receptors. In diabetic rats treated with anakinra (100 or 160 mg/Kg/day for 3 or 7 days before sacrifice) a partial improvement of diabetic endothelial dysfunction occurred, together with a reduction of vascular NADPH oxidase and NF-κB activation. Endothelial dysfunction in diabetic animals was also associated to higher activities of the pro-inflammatory enzymes cyclooxygenase (COX) and the inducible isoform of nitric oxide synthase (iNOS), which were markedly reduced after anakinra treatment. Circulating IL-1β and TNF-α levels did not change in diabetic rats, but they were lowered by anakinra treatment.

Conclusions

In this short-term model of type 1 diabetes, endothelial dysfunction is associated to an IL-1 receptor-mediated activation of vascular NADPH oxidase and NF-κB, as well as to vascular inflammation. Moreover, endothelial dysfunction, vascular oxidative stress and inflammation were reduced after anakinra treatment. Whether this mechanism can be extrapolated to a chronic situation or whether it may apply to diabetic patients remain to be established. However, it may provide new insights to further investigate the therapeutic use of IL-1 receptor antagonists to obtain vascular benefits in patients with diabetes mellitus and/or atherosclerosis.

Naltrexone attenuates endoplasmic reticulum stress induced hepatic injury in mice

Endoplasmic reticulum (ER) stress provides abnormalities in insulin action, inflammatory responses, lipoprotein B100 degradation and hepatic lipogenesis. Excess accumulation of triglyceride in hepatocytes may also lead to disorders such as non-alcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Opioid peptides are involved in triglyceride and cholesterol dysregulation, inflammation and cell death. In this study, we evaluated Naltrexone effects on ER stress induced liver injury. To do so, C57/BL6 mice received saline, DMSO and Naltrexone, as control groups. ER stress was induced by tunicamycin (TM) injection. Naltrexone was given before TM administration. Liver blood flow and biochemical serum analysis were measured. Histopathological evaluations, TNF-α measurement and Real-time RT-PCR were also performed. TM challenge provokes steatosis, cellular ballooning and lobular inflammation which significantly reduced in Naltrexone treated animals. ALT, AST and TNF-α increased in the TM group and improved in the Naltrexone plus TM group. Triglyceride and cholesterol levels decreased in TM treated mice with no increase in Naltrexone treated animals. In the Naltrexone plus TM group, gene expression of Bax/Bcl-2 ratio and caspase3 significantly lowered compared with the TM group. In this study, we found that Naltrexone had a notable alleviating role in ER stress induced steatosis and liver injury.

Interleukin-1 signaling pathway as a therapeutic target in transthyretin amyloidosis

INTRODUCTION

Inflammation is a key pathological hallmark of several neurodegenerative disorders including Alzheimer's disease, Parkinson's disease and familial amyloidotic polyneuropathy (FAP). Among all inflammatory cytokines associated with FAP, IL-1β, in particular, has been implicated in playing a key pathogenic role. In the present study, we sought to investigate whether blocking IL-1β signaling provides disease-modifying benefits in an FAP mouse model.

METHODS

We assessed the effect of chronic administration of Anakinra, an IL-1 antagonist, on FAP pathogenesis in vivo, using real-time polymerase chain reaction (qPCR), semi-quantitative immunohistochemistry (SQ-IHC), western blot and nerve morphometric analyses.

RESULTS

We found that treatment with Anakinra prevents transthyretin (TTR) extracellular deposition in sciatic nerve, protecting unmyelinated nerve fibers from aggregate-induced degeneration. Moreover, Anakinra administration significantly suppressed IL-1 signaling pathway and inhibited apoptosis and nitrative stress.

CONCLUSIONS

The present work highlights the relevance of the IL-1 signaling pathway in the pathophysiology of FAP. Our results bring to light the importance of non-amyloid targets in the therapeutic strategies for this disorder. Thus, we propose the use of Anakinra as a potential therapeutic agent for TTR-related amyloidosis.

Modulation of endothelial cell migration by ER stress and insulin resistance: a role during maternal obesity?

Adverse microenvironmental stimuli can trigger the endoplasmic reticulum (ER) stress pathway, which initiates the unfolded protein response (UPR), to restore protein-folding homeostasis. Several studies show induction of ER stress during obesity. Chronic UPR has been linked to different mechanisms of disease in obese and diabetic individuals, including insulin resistance (IR) and impaired angiogenesis. Endothelial cell (EC) migration is an initial step for angiogenesis, which is associated with remodeling of existing blood vessels. EC migration occurs according to the leader–follower model, involving coordinated processes of chemotaxis, haptotaxis, and mechanotaxis. Thus, a fine-tuning of EC migration is necessary to provide the right timing to form the required vessels during angiogenesis. ER stress modulates EC migration at different levels, usually impairing migration and angiogenesis, although different effects may be observed depending on the tissue and/or microenvironment. In the context of pregnancy, maternal obesity (MO) induces IR in the offspring. Interestingly, several proteins associated with obesity-induced IR are also involved in EC migration, providing a potential link with the ER stress-dependent alterations observed in obese individuals. Different signaling cascades that converge on cytoskeleton regulation directly impact EC migration, including the Akt and/or RhoA pathways. In addition, ER is the main intracellular reservoir for Ca²⁺, which plays a pivotal role during EC migration. Therefore, ER stress-related alterations in Ca²⁺ signaling or Ca²⁺ levels might also produce distorted EC migration. However, the above findings have been studied in the context of adult obesity, and no information has been reported regarding the effect of MO on fetal EC migration. Here we summarize the state of knowledge about the possible mechanisms by which ER stress and IR might impact EC migration and angiogenesis in fetal endothelium exposed to MO during pregnancy.

Endoplasmic reticulum stress and endothelial dysfunction

Prolonged perturbation of the endoplasmic reticulum (ER) leads to ER stress and unfolded protein response (UPR) and contributes to the pathogenesis of various chronic disorders. This review focuses on the role of ER stress and UPR in endothelial cells and the relevance of these processes to vascular diseases. Chronic activation of ER stress and UPR pathways in endothelial cells leads to increased oxidative stress and inflammation and often results in cell death. Because endothelial cells play a pivotal role in maintaining vascular homeostasis, various pathological conditions interfering with this homeostasis including homocysteinemia, hyperlipidemia, high glucose, insulin resistance, disturbed blood flow, and oxidative stress can lead to endothelial dysfunction in part through the activation of ER stress. We discuss recently discovered aspects of the role of ER stress/UPR in those pathological conditions. We also summarize recent findings implicating ER stress and UPR in systemic hypertension as well as pulmonary arterial hypertension. Finally, this review will highlight a novel role of UPR mediators in the process of angiogenesis.

Coping with endoplasmic reticulum stress in the cardiovascular system

The endoplasmic reticulum (ER) is a multifunctional intracellular organelle, a component of the cellular reticular network that allows cells to adjust to a wide variety of conditions. The cardiomyocyte reticular network is the ideal location of sensors for both intrinsic and extrinsic factors that disrupt energy and/or nutrient homeostasis and lead to ER stress, a disturbance in ER function. ER stress has been linked to both physiological and pathological states in the cardiovascular system; such states include myocardial infarction, oxygen starvation (hypoxia) and fuel starvation, ischemia, pressure overload, dilated cardiomyopathy, hypertrophy, and heart failure. The ER stress coping response (e.g., the unfolded protein response) is composed of discrete pathways that are controlled by a collection of common regulatory components that may function as a single entity involved in reacting to ER stress. These corrective strategies allow the cardiomyocyte reticular network to restore energy and/or nutrient homeostasis and to avoid cell death. Therefore, the identities of the ER stress corrective strategies are important targets for the development of therapeutic approaches for cardiovascular and other acquired disorders.