Cryptotanshinone,an orally bioactive herbal compound from Danshen,attenuates atherosclerosis in apolipoprotein E‐deficient mice: role of lectin‐like oxidized LDL receptor‐1 (LOX‐1)

Background and Purpose

Cryptotanshinone (CTS) is a major bioactive diterpenoid isolated from Danshen, an eminent medicinal herb that is used to treat cardiovascular disorders in Asian medicine. However, it is not known whether CTS can prevent experimental atherosclerosis. The present study was designed to investigate the protective effects of CTS on atherosclerosis and its molecular mechanisms of action.

Experimental Approach

Apolipoprotein E‐deficient (ApoE ^−/−) mice, fed an atherogenic diet, were dosed daily with CTS (15, 45 mg kg⁻¹ day⁻¹) by oral gavage. In vitro studies were carried out in oxidized LDL (oxLDL)‐stimulated HUVECs treated with or without CTS.

Key Results

CTS significantly attenuated atherosclerotic plaque formation and enhanced plaque stability in ApoE ^−/− mice by inhibiting the expression of lectin‐like oxLDL receptor‐1 (LOX‐1) and MMP‐9, as well as inhibiting reactive oxygen species (ROS) generation and NF‐κB activation. CTS treatment significantly decreased the levels of serum pro‐inflammatory mediators without altering the serum lipid profile. In vitro, CTS decreased oxLDL‐induced LOX‐1 mRNA and protein expression and, thereby, inhibited LOX‐1‐mediated adhesion of monocytes to HUVECs, by reducing the expression of adhesion molecules (intracellular adhesion molecule 1 and vascular cellular adhesion molecule 1). Furthermore, CTS inhibited NADPH oxidase subunit 4 (NOX4)‐mediated ROS generation and consequent activation of NF‐κB in HUVECs.

Conclusions and Implications

CTS was shown to have anti‐atherosclerotic activity, which was mediated through inhibition of the LOX‐1‐mediated signalling pathway. This suggests that CTS is a vasculoprotective drug that has potential therapeutic value for the clinical treatment of atherosclerotic cardiovascular diseases.

Linked Articles

This article is part of a themed section on Chinese Innovation in Cardiovascular Drug Discovery. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-23

Abbreviations

ApoE^−/−

apolipoprotein E deficient

CD36

cluster of differentiation 36

CTS

cryptotanshinone

HCD

high cholesterol diet

ICAM‐1

intracellular adhesion molecule 1

LOX‐1

lectin‐like oxidized low‐density lipoprotein receptor‐1

NOX4

NADPH oxidase subunit 4

oxLDL

oxidized low‐density lipoprotein

ROS

reactive oxygen species

SMCs

smooth muscle cells

SR‐A

scavenger receptor‐A

VCAM‐1

vascular cellular adhesion molecule 1

Tables of Links

γ-Oryzanol protects against acute cadmium-induced oxidative damage in mice testes

Cadmium is a non-essential heavy metal that is present at low levels mainly in food and water and also in cigar smoke. The present study evaluated the testicular damage caused by acute cadmium exposure and verified the protective role of γ-oryzanol (ORY). Mice were administrated with a single dose of 2.5 mg/kg of CdCl₂, and then treated with ORY (50 mM in canola oil, 5 mL/kg). Testes were removed after 24 h and tested for lipid peroxidation (TBARS), protein carbonylation, DNA breakage, ascorbic acid, cadmium and non-proteic thiols contents, and for the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST) and δ-aminolevulic acid dehydratase (δ-ALA-D). Cadmium presented a significant alteration in all parameters, except GPx and CAT activities. Therapy reduced in a slight degree cadmium concentration in testes (around 23%). ORY restored SOD and GST activities as well as TBARS production to the control levels. Furthermore, ORY partially recovered δ-ALA-D activity inhibited by cadmium. This study provides the first evidence on the therapeutic properties of ORY in protecting against cadmium-induced testicular toxicity.     

Ergothioneine protects against neuronal injury induced by β-amyloid in mice

β-Amyloid peptides (Aβ) are neurotoxic and contribute to the development of Alzheimer’s disease (AD). Ergothioneine (EGT) has been shown to protect against loss of memory and learning abilities in mice. In this study, mice were orally fed EGT (0.5 or 2 mg/kg body weight) for 16 days before treatment (i.c.v) with a single dose of Aβ1–40 in the hippocampus. After resting for 12 days to restore the body weight, the mice were again fed EGT for additional 39 days. Active avoidance tests were conducted on days 37–39 (short-memory avoidance) and on days 37, 44 and 51 (long-memory avoidance). Water maze task was used to evaluate learning and memory abilities by acquisition test and retention test. In both long-memory avoidance and water maze tests, EGT significantly decreased the escape latency and increased the frequency of successful avoidance. Furthermore, EGT significantly prevented Aβ accumulation in the hippocampus and brain lipid peroxidation, restored acetylcholinesterase (AChE) activity, maintained glutathione/glutathione disulfide ratio and superoxide dismutase activity in brain tissues of Aβ1–40-teated mice. Thus, EGT can protect against Aβ-induced loss of memory and learning abilities in mice. Further studies are required to confirm the protective effects of EGT on the development or progression of AD.     

（5R）-5-hydroxytriptolide （LLDT-8） protects against bleomycin-induced lung fibrosis in mice

AIM: To study the protective effects of a triptolide-derived, novel compound, (5R)-5-hydroxytriptolide (LLDT-8), on bleomycin-induced lung fibrosis. METHODS: C57BL/6 mice received an intratracheal injection of bleomycin and were then treated with LLDT-8 (0.5, 1, 2 mg/kg, ip) once daily for 7 or 14 consecutive days. The body weight loss and lung index augmentation was observed; the inflammatory response including differential cells counts of neutrophils, macrophages, and lymphocytes in the bronchoalveolar lavage fluid (BALF), superoxide dismutase (SOD), and malondialdehyde (MDA) level in the lung homogenates was detected, and the fibrosis extent was evaluated by hydroxyproline content and histopathological changes in the lungs. In addition, the pro-inflammatory and pro-fibrotic cytokines, tumor necrosis factor-alpha (TNF-alpha), interleukin-4 (IL-4), and transforming growth factor-alpha (TGF-alpha) production in the lungs were measured. RESULTS: LLDT-8 alleviated the body weight loss and lung index increase caused by bleomycin, reduced neutrophils and lymphocytes in the BALF, promoted SOD activity, decreased MDA production, and inhibited the hydroxyproline level and the amelioration of lung tissue histological damage. Moreover, LLDT-8 suppressed TNF-alpha, IL-4, and TGF-beta production in the lung homogenates. CONCLUSION: LLDT-8 showed protective effects against bleomycin-induced lung fibrosis, and the results suggested the potential role of LLDT-8 in the treatment of this disease.     

GYY4137 exhibits anti-atherosclerosis effect in apolipoprotein E (−/−) mice via PI3K/Akt and TLR4 signalling

Hydrogen sulphide (H₂S) had been suggested to be involved in the pathogenesis of atherosclerosis, but the underlying molecular mechanisms are poorly understood. In this study, we aimed to investigate the anti-atherosclerosis effect of morpholin-4-ium-methoxyphenyl-morpholino-phosphinodithioate (GYY4137) in RAW264.7 cell-derived foam cells formation and in the atherosclerotic plaque of ApoE−/− mice fed with a high-fat diet, and study the underlying mechanisms of phosphatidylinositol 3-kinase (PI3K), serine/ threonine kinase (Akt) and Toll-like receptor 4 (TLR4) signalling pathway. In the ApoE−/− mice fed with a high-fat diet, daily GYY4137 administration for 8 weeks effectively decreased carotid atherosclerotic plaque area and the volume of foam cells, regulated the lipid metabolism, down-regulated the pro-inflammatory cytokine levels and up-regulated the anti-inflammatory cytokines levels. Consistent with these findings, in the RAW264.7 cell-derived foam cells, GYY4137 ameliorated foam cell formation in vitro, and decreased the expression of pro-inflammatory cytokines. Furthermore, our studies showed that GYY4137 could activate the PI3K/Akt signalling pathway and consequently reduce the expression of TLR4 to be critical for foam cell formation, preventing atherosclerotic plaque formation and destabilization. LY294002, a PI3K inhibitor, could inhibit the phosphorylation of Akt and reduce the expression of TLR4, thus reduce the foam cell source and lipid volume in the unstable plaque tissue. Our results suggest that GYY4137 is an attractive novel therapeutic reagent for atherosclerosis diseases. This mechanism may be partially attributed to regulating the PI3K/Akt/TLR4 signalling pathway.     

Stimulation of α7 nicotinic acetylcholine receptor by AR-R17779 suppresses atherosclerosis and aortic aneurysm formation in apolipoprotein E-deficient mice

Atherosclerosis is a chronic inflammatory disease. It has been appreciated that vagus nerve inhibits macrophage activation via α7 nicotinic acetylcholine receptor (nAChR), termed the cholinergic anti-inflammatory pathway. We explored the effects of AR-R17779, a selective α7nAChR agonist, on atherosclerosis and aneurysm formation in apolipoprotein E (ApoE)-deficient mice. ApoE-deficient mice were fed a high-fat diet (HFD) and angiotensin II (Ang II) was infused by osmotic minipumps from 10-week-old for 4 weeks. AR-R17779 was given in drinking water ad libitum. Oil red O staining of the aorta showed that combined loading of HFD and Ang II induced marked atherosclerosis compared with control mice fed a normal chow. Treatment with AR-R17779 significantly reduced atherosclerotic plaque area and improved survival of mice. Treatment with AR-R17779 also suppressed abdominal aortic aneurysm formation. Quantitative RT-PCR of the aorta revealed that mRNA expression levels of interleukin-1β, interleukin-6 and NOX2 were significantly decreased in AR-R17779-treated mice compared with Ang II + HFD mice. AR-R17779 treatment also reduced blood pressure and serum lipid levels. In conclusion, α7nAChR activation attenuates atherogenesis and aortic abdominal aneurysm formation in ApoE-deficient mice possibly through an anti-inflammatory effect and reduction of blood pressure and lipid levels. Pharmacological activation of α7nAChR may have a therapeutic potential against atherosclerotic vascular diseases through multiple mechanisms.     

Cryptotanshinone protects against IL-1β-induced inflammation in human osteoarthritis chondrocytes and ameliorates the progression of osteoarthritis in mice

Osteoarthritis (OA) is a common degenerative disease characterized by progressive erosion of articular cartilage, subchondral bone sclerosis and synovitis. Cryptotanshinone (CTS), an active component extracted from the root of Salvia miltiorrhiza Bunge, has been shown to have potent anti-inflammatory effects. However, its effects on OA have not been clearly elucidated. This study aimed to assess the effect of CTS on human OA chondrocytes and mice OA models. Human OA chondrocytes were pretreated with CTS (5, 10 and 20 μM) for 2 h and subsequently stimulated with IL-1β for 24 h. Production of NO, PGE2, IL-6, TNF-α was evaluated by the Griess reaction and ELISA. The protein expression of COX-2, iNOs, MMP-3, MMP13, COX-2, ADAMTS-5, JNK, p-JNK, ERK, p-ERK, p38, p-p38, p-IKKα/β, p65, p-p65, IκB-α, and p-IκB-α was tested by Western blot. In vivo, the severity of OA was determined by histological analysis. We found that CTS significantly inhibited the IL-1β-induced production of NO and PGE2; expression of COX-2, iNOS, MMP-3, MMP-13, and ADAMTS-5. Furthermore, CTS in dramatically suppressed IL-1β-stimulated NF-κB and MAPK activation. Immunofluorescence staining demonstrated that CTS could suppress IL-1β-induced phosphorylation of p65 nuclear translocation. In vivo, treatment of CTS prevented the destruction of cartilage and the thickening of subchondral bone in mice OA models. These results indicate that the therapeutic effect of CTS on OA is accomplished through the inhibition of both NF-κB and MAPK signaling pathways. Our findings provide the evidence to develop CTS as a potential therapeutic agent f or patients with OA.     

Mangiferin antagonizes TNF-α-mediated inflammatory reaction and protects against dermatitis in a mice model

This study aimed to investigate whether mangiferin played a protective role in a well-established dermatitis mouse model and tumor necrosis factor alpha (TNF-α)-induced RAW264.7 macrophages. Contact dermatitis is an inflammatory skin disease in the clinic, while its underlying mechanism still remains to be elucidated. Mangiferin, 1,3,6,7-tetrahydroxyxanthone-C2-β-d-glucoside (C-glucosyl xanthone), a natural antioxidant that was reported to inhibit inflammatory reactions, has been recently proved to be a potential therapy for inflammation. As a result, the oxazolone-induced dermatitis mice models were established to explore whether mangiferin has an anti-inflammatory role in vivo. The phosphate-buffered saline treatment groups showed emblematic skin inflammation, whereas the administration of mangiferin obviously inhibited dermatitis in the mice models. Furthermore, exogenous mangiferin alleviated the inflammatory reaction in TNF-α-induced macrophages by suppressing the production of inflammation- and oxidative stress–associated molecules. Also, mangiferin treatment repressed the activation of nuclear factor-kappaB signaling pathway. To sum up, mangiferin could provide a new target for the therapy and prevention of skin inflammation.     

Expression of miRNA-155 in carotid atherosclerotic plaques of apolipoprotein E knockout (ApoE−/−) mice and the interventional effect of rapamycin

Carotid atherosclerosis (AS) is an inflammatory process and is the primary pathogenesis of cerebrovascular disease. Many factors are responsible for development of atherosclerosis such as inflammation and autophagy. It is reported that microRNAs (miRNAs) could regulate the development of atherosclerosis through targeting autophagy-related genes. Many studies have demonstrated that miRNA-155 could regulate autophagy in macrophages or tumor cells. However, the role of miRNA-155 on autophagy in carotid plaques is not yet known. In this study, we explore the expression of miRNA-155 and autophagy-related proteins in carotid plaques of ApoE^−/− mice and the interventional effect of rapamycin. We compared the expression of miRNA-155 and autophagy-related proteins between the control, model and rapamycin groups using qRT-PCR and western blot. Compared to the control group, we found the miRNA-155 and LC3-II expression was up-regulated (P < 0.05), expression ratio of phosphorylated mammalian target of rapamycin to total mammalian target of rapamycin (p-mTOR/mTOR) was down-regulated in model group (P < 0.05), but atherosclerotic lesions were still aggravated. These results following rapamycin group indicated that miRNA-155 and LC3-II expression was significantly up-regulated (P < 0.05), the expression ratio of p-mTOR/mTOR was significantly down-regulated (P < 0.05), and atherosclerotic lesions were reduced. Our results showed in the early stages of atherosclerotic plaques development, effective autophagy could attenuate atherosclerosis in ApoE^−/− mice. Furthermore, our results also demonstrated that rapamycin might promote the activation of the autophagy by enhancing the expression of miRNA-155, which delays the development of atherosclerotic plaques.     

Inhibition of GPR17 with pranlukast protects against TNF-α-induced loss of type II collagen in ATDC5 cells

Osteoarthritis (OA) is a common joint disease affecting millions of elderly people worldwide. However, the mechanism of OA is complicated and remains poorly understood. Thus, a safe and effective therapeutic strategy has yet to be developed. G protein-coupled receptor 17 (GPR17) is an orphan receptor that is widely distributed in the central nervous system (CNS). GPR17 has become a target for the treatment of inflammation in brain diseases. In this study, we demonstrate that GPR17 is expressed in ATDC5 cells and is increased in response to TNF-α exposure. We also found that antagonism of GPR17 with pranlukast significantly inhibited oxidative stress by downregulating the intracellular level of reactive oxygen species (ROS) and increasing the activity of super oxide dismutase (SOD) against TNF-α. Interestingly, treatment with pranlukast prevented TNF-α-induced reduction of type II collagen. Additionally, knockdown of GPR17 with siRNA ameliorated TNF-α-induced loss of type II collagen, suggesting the importance of the role of GPR17 in mediating the impairment of type II collagen. Blockage of GPR17 with pranlukast suppressed the expression of matrix metalloproteinases 3 (MMP-3) and matrix metalloproteinases 13 (MMP-13), which contribute to the degradation of type II collagen. Pranlukast also prevented the activation of the JAK2/STAT1/IRF-1 signaling pathway, thereby suppressing the expression of pro-inflammatory cytokines and enzymes. Furthermore, pranlukast rescued TNF-α-induced reduced SOX-9 expression. Together, our data indicate that GPR17 might be a potential target for the treatment of OA.     

Acetyl-α-boswellic acid and Acetyl-β-boswellic acid protects against caerulein-induced pancreatitis via down-regulating MAPKs in mice

This study is to investigate the protective effect of Acetyl-α-boswellic acid and Acetyl-β-boswellic mixture(α/β-ABA), which is the active ingredients isolated from Frankincense, on actue pancreatitis and its mechanism. Our experimental results showed that 2 μM α/β-ABA reduced production of NO, TNF-α, IL-6, IL-10 and IL-1β in RAW264.7 cells that were stimulated with lipopolysaccharide (LPS) which indicates its anti-inflammatory role. In pancreatitis model induced by caerulein, intra-gastrical administration of 100 mg/kg α/β-ABA relieved inflammatory cells infiltration significantly and attenuated the serum elevation of amylase TNF-α and IL-6 remarkably in mice. Furthermore, α/β-ABA down-regulated mitogen-activated protein kinase (MAPK) family phosphorylated proteins in pancreas, including phosphorylated p38, ERK1/2 and JNK, to reduce the serum inflammatory factors. Finally, α/β-ABA alleviated the pancreatic edema and inflammatory cell infiltration in pancreatitis mice model. This study suggests that α/β-ABA may be targeted for drug development against pancreatitis via modulating MAPKs pathway.     

Lidocaine attenuates lipopolysaccharide-induced inflammatory responses and protects against endotoxemia in mice by suppressing HIF1α-induced glycolysis

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infections. Previous studies have indicated that lidocaine, an amide local anesthetic, has anti-inflammatory properties; however, the underlying mechanism remains unclear. In this study, we have shown that lidocaine dose-dependently inhibits lipopolysaccharide (LPS)-induced production of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) in macrophages and that lidocaine protects mice from LPS-induced inflammation. Moreover, we have demonstrated that lidocaine reduces the release of TNF-α and IL-6 through the reduction of the expression of GLUT1 and HK2 to further suppress HIF1α-induced aggravation of inflammatory cascades. Lidocaine can inhibit the enhanced glycolysis and glycolytic capacity induced by LPS in the macrophages. As an inhibitor of PHDs (prolyl hydroxylases), Dimethyloxalylglycine (DMOG) can reduce the anti-inflammatory effects of lidocaine. In conclusion, the present study indicates that lidocaine can be used as a potential therapeutic agent for sepsis.     

Effect of telmisartan on expression of protein kinase C-α in kidneys of diabetic mice

Aim： To investigate the effects of angiotensin receptor blocker （ARB） telmisartan on the expression and distribution of protein kinase C （PKC）-α in the kidneys of diabetic mice. Methods： Diabetic mice were induced with streptozotocin and a group of them were randomly selected for treatment with telmisartan. After 6 weeks, the expression and localization of PKC-α in the renal cortex, and the outer and inner medulla were assessed by immunohistochemistry and semiquantitative Western blotting. In addition, expressions of PKC-α, transforming growth factor- β1 （TGF-β1）, and vascular endothelial growth factor （VEGF） in glomeruli were measured by semiquantitative immunohistochemistry. Results： Diabetic and normal mice showed similar distributions of PKC-α in the kidneys. The expression of PKC-α was found in glomeruli, epithelial cells of proximal tubules, and medullary- collecting duct, while not in the medullary and cortical thick ascending limb, and was different in the epithelial cells of proximal tubules of diabetic nephropathy （DN） mice, PKC-α was mostly translocated from the basement membrane to the apical membrane, whereas it was largely translocated from the apical membrane to the basement membrane in epithelial cells of the inner medullary-collecting duct. Western blotting detected increased expression of PKC-α in the renal cortex and outer medulla, but not in the inner medulla of DN mice. Enhanced expressions of PKC-α, TGF-β1, and VEGF were shown in the glomeruli of DN mice, where PKC-α exhibited a correlation to VEGF, but no correlation to TGF-β1. ARB telmisartan attenuated alterations of PKC-α as mentioned earlier in the DN mice. Conclusion： Our findings suggest that PKC-α may play a role in the pathogenesis of DN, and that the nephroprotective effects of ARB telmisartan may be partly associated with its influence on PKC-α.     

Protective effects of stigmasterol against ketamine‐induced psychotic symptoms: Possible behavioral,biochemical and histopathological changes in mice

Background

Stigmasterol, a naturally occurring phytoestrogen has been reported to possess many pharmacological activities. The aim of the present study was to screen the effect of stigmasterol against ketamine-induced mice model of psychosis.

Inhibition of spleen tyrosine kinase signaling protects against acute lung injury through blockade of NADPH oxidase and IL-17A in neutrophils and γδ T cells respectively in mice

Acute lung injury (ALI) is one of the most serious complications in critically ill patients which often leads to morbidity and mortality. ALI characterized by severe inflammation of lungs occurs due to uncontrolled inflammatory immune response. However, the immunological mechanism(s) are far from being understood. The spleen tyrosine kinase (SYK), a key component of immune receptor signaling, plays a critical role in the modulation of inflammatory signaling in different immune cells. However, its role in ALI remains to be explored. Therefore, in this study, we investigated the effect of R406, a SYK inhibitor in lipopolysaccharide (LPS)-induced ALI mouse model. LPS led to increased SYK expression in neutrophils and gamma delta (γδ) T cells. This was associated with increased neutrophilic airway inflammation, vascular permeability, myeloperoxidase activity in the lung with upregulated expression of NADPH oxidase (NOX2)/MCP-1/TNF-α in neutrophils and IL-17A in γδ T cells/lung. Pulmonary inflammation was associated with higher mortality in mice with ALI. Inhibition of SYK signaling using R406 in the lung led to blockade of neutrophilic airway inflammation, vascular permeability, pro-inflammatory cytokine release and oxidative stress in innate immune cells, i.e. γδ T cells and neutrophils and the lung. R406 administered LPS group had better survival rate than LPS group. This suggests that SYK upregulation in γδ T cells and neutrophils plays an important role in inflammatory process during ALI. In conclusion, R406 exhibited a great potential to block the LPS-induced airway inflammation and mortality which could be developed as a potential future therapy in ALI.     

The hydrogen sulfide donor,GYY4137, exhibits anti-atherosclerotic activity in high fat fed apolipoprotein E?/? mice

Background and Purpose

Atherosclerosis is associated with reduced vascular hydrogen sulfide (H₂S) biosynthesis. GYY4137 is a novel slow-releasing H₂S compound that may effectively mimic the time course of H₂S release in vivo. However, it is not known whether GYY4137 affects atherosclerosis.

Experimental Approach

RAW 264.7 cells and human blood monocyte-derived macrophages were incubated with oxidized low density lipoprotein (ox-LDL) with/without GYY4137. ApoE^−/− mice were fed a high-fat diet for 4 weeks and administered GYY4137 for 30 days. Lipid and atherosclerotic lesions were measured by oil red O staining. Endothelium-dependent relaxation was assessed in response to acetylcholine. Superoxide production was detected by dihydroethidium staining. Expression of mRNA and protein were evaluated by quantitative real-time PCR and Western blot.

Key Results

GYY4137 inhibited ox-LDL-induced foam cell formation and cholesterol esterification in cultured cells. GYY4137 decreased the expression of lectin-like ox-LDL receptor-1, iNOS, phosphorylated IκBα, NF-κB, ICAM-1, VCAM-1 and chemokines, including CXCL2, CXCR4, CXCL10 and CCL17, but increased the scavenger protein CD36, in ox-LDL-treated RAW 264.7 cells. In vivo, GYY4137 decreased aortic atherosclerotic plaque formation and partially restored aortic endothelium-dependent relaxation in apoE^−/− mice. GYY4137 decreased ICAM-1, TNF-α and IL-6 mRNA expression as well as superoxide (O₂⁻) generation in aorta. In addition, GYY4137 increased aortic eNOS phosphorylation and expression of PI3K, enhanced Akt Ser⁴⁷³ phosphorylation and down-regulated the expression of LOX-1.

Conclusion and Implications

GYY4137 inhibits lipid accumulation induced by ox-LDL in RAW 264.7 cells. In vivo, GYY4137 decreased vascular inflammation and oxidative stress, improved endothelial function and reduced atherosclerotic plaque formation in apoE^−/− mice.     

Nicotinamide-rich diet protects the heart against ischaemia–reperfusion in mice: A crucial role for cardiac SUR2A

It is a consensus view that a strategy to increase heart resistance to ischaemia–reperfusion is a warranted. Here, based on our previous study, we have hypothesized that a nicotinamide-rich diet could increase myocardial resistance to ischaemia–reperfusion. Therefore, the purpose of this study was to determine whether nicotinamide-rich diet would increase heart resistance to ischaemia–reperfusion and what is the underlying mechanism. Experiments have been done on mice on control and nicotinamide-rich diet (mice were a week on nicotinamide-rich diet) as well as on transgenic mice overexpressing SUR2A (SUR2A mice), a regulatory subunit of cardioprotective ATP-sensitive K⁺ (K_ATP) channels and their littermate controls (WT). The levels of mRNA in heart tissue were measured by real-time RT-PCR, whole heart and single cell resistance to ischaemia–reperfusion and severe hypoxia was measured by TTC staining and laser confocal microscopy, respectively. Nicotinamide-rich diet significantly decreased the size of myocardial infarction induced by ischaemia–reperfusion (from 42.5 ± 4.6% of the area at risk zone in mice on control diet to 26.8 ± 1.8% in mice on nicotinamide-rich diet, n = 6–12, P = 0.031). The cardioprotective effect of nicotinamide-rich diet was associated with 11.46 ± 1.22 times (n = 6) increased mRNA levels of SUR2A in the heart. HMR1098, a selective inhibitor of the sarcolemmal K_ATP channels opening, abolished cardioprotection afforded by nicotinamide-rich diet. Transgenic mice with a sole increase in SUR2A expression had also increased cardiac resistance to ischaemia–reperfusion. We conclude that nicotinamide-rich diet up-regulate SUR2A and increases heart resistance to ischaemia–reperfusion.