Effect of lipoxin A4 on myocardial ischemia reperfusion injury following cardiac arrest in a rabbit model

Lipoxins and their relationship with inflammation-associated diseases. A systematic review

AIM

To determine the relationship of lipoxin levels with inflammation and disease development in adults and children.

METHODS

We conducted a systematic review. The search strategy included Medline, Ovid, EMBASE, LILACS, The Cochrane Central Register of Controlled Trials, and Open Gray. We included Clinical trials, cohort studies, case-control studies, and cross-sectional studies. Animal experiments were excluded.

RESULTS

We included fourteen studies in this review, nine consistently showing decreased lipoxin levels and anti-inflammatory markers or increased pro-inflammatory markers in cardiovascular disease, metabolic syndrome, Alzheimer's disease, periodontitis, or autism. Five studies showed increased lipoxin levels and pro-inflammatory markers in pre-eclampsia, asthma, and coronary disease. On the other hand, one showed increased lipoxin levels and decreased pro-inflammatory marker levels.

CONCLUSIONS

Decreases in lipoxins are associated with developing pathologies such as cardiovascular and neurological diseases, indicating that lipoxins protect against these pathologies. However, in other pathologies, such as asthma, pre-eclampsia, and periodontitis, which are associated with chronic inflammation despite increased levels of LXA4, the increase in inflammation suggests a possible failure of this regulatory pathway. Therefore, further studies are necessary to evaluate the role of LXA4 in the pathogenesis of inflammatory diseases.

Clinical significance of polyunsaturated fatty acids in the prevention of cardiovascular diseases

Cardiovascular diseases are one of the most important problems of modern medicine. They are associated with a large number of health care visits, hospitalizations and mortality. Prevention of atherosclerosis is one of the most effective strategies and should start as early as possible. Correction of lipid metabolism disorders is associated with definite clinical successes, both in primary prevention and in the prevention of complications of many cardiovascular diseases. A growing body of evidence suggests a multifaceted role for polyunsaturated fatty acids. They demonstrate a variety of functions in inflammation, both participating directly in a number of cellular processes and acting as a precursor for subsequent biosynthesis of lipid mediators. Extensive clinical data also support the importance of polyunsaturated fatty acids, but all questions have not been answered to date, indicating the need for further research.

Manganese Porphyrin Promotes Post Cardiac Arrest Recovery in Mice and Rats

Introduction Cardiac arrest (CA) and resuscitation induces global cerebral ischemia and reperfusion, causing neurologic deficits or death. Manganese porphyrins, superoxide dismutase mimics, are reportedly able to effectively reduce ischemic injury in brain, kidney, and other tissues. This study evaluates the efficacy of a third generation lipophilic Mn porphyrin, MnTnBuOE-2-PyP5+, Mn(III) ortho meso-tetrakis (N-n-butoxyethylpyridinium-2-yl)porphyrin (MnBuOE, BMX-001), in both mouse and rat models of CA. Methods Forty-eight animals were subjected to 8 min of CA and resuscitated subsequently by chest compression and epinephrine infusion. Vehicle or MnBuOE was given immediately after resuscitation followed by daily subcutaneous injections. Body weight, spontaneous activity, neurologic deficits, rotarod performance, and neuronal death were assessed. Kidney tubular injury was assessed in CA mice. Data were collected by the investigators who were blinded to the treatment groups. Results Vehicle mice had a mortality of 20%, which was reduced by 50% by MnBuOE. All CA mice had body weight loss, spontaneous activity decline, neurologic deficits, and decreased rotarod performance that were significantly improved at three days post MnBuOE daily treatment. MnBuOE treatment reduced cortical neuronal death and kidney tubular injury in mice (p < 0.05) but not hippocampus neuronal death (23% MnBuOE vs. 34% vehicle group, p = 0.49). In rats, they had a better body-weight recovery and increased rotarod latency after MnBuOE treatment when compared to vehicle group (p < 0.01 vs. vehicle). MnBuOE-treated rats had a low percentage of hippocampus neuronal death (39% MnBuOE vs. 49% vehicle group, p = 0.21) and less tubular injury (p < 0.05) relative to vehicle group. Conclusions We demonstrated the ability of MnBuOE to improve post-CA survival, as well as functional outcomes in both mice and rats, which jointly account for the improvement not only of brain function but also of the overall wellbeing of the animals. While MnBuOE bears therapeutic potential for treating CA patients, the females and the animals with comorbidities must be further evaluated before advancing toward clinical trials.

Molecular Pharmacology of Inflammation Resolution in Atherosclerosis

Atherosclerosis is one of the most important problems of modern medicine as it is the leading cause of hospitalizations, disability, and mortality. The key role in the development and progression of atherosclerosis is the imbalance between the activation of inflammation in the vascular wall and the mechanisms of its control. The resolution of inflammation is the most important physiological mechanism that is impaired in atherosclerosis. The resolution of inflammation has complex, not fully known mechanisms, in which lipid mediators derived from polyunsaturated fatty acids (PUFAs) play an important role. Specialized pro-resolving mediators (SPMs) represent a group of substances that carry out inflammation resolution and may play an important role in the pathogenesis of atherosclerosis. SPMs include lipoxins, resolvins, maresins, and protectins, which are formed from PUFAs and regulate many processes related to the active resolution of inflammation. Given the physiological importance of these substances, studies examining the possibility of pharmacological effects on inflammation resolution are of interest.

Specialized Proresolving Lipid Mediators: A Potential Therapeutic Target for Atherosclerosis

Cardiovascular disease (CVD) is a global public health issue due to its high morbidity, mortality, and economic impact. The implementation of innovative therapeutic alternatives for CVD is urgently required. Specialized proresolving lipid mediators (SPMs) are bioactive compounds derived from ω-3 and ω-6 fatty acids, integrated into four families: Lipoxins, Resolvins, Protectins, and Maresins. SPMs have generated interest in recent years due to their ability to promote the resolution of inflammation associated with the pathogeneses of numerous illnesses, particularly CVD. Several preclinical studies in animal models have evidenced their ability to decrease the progression of atherosclerosis, intimal hyperplasia, and reperfusion injury via diverse mechanisms. Large-scale clinical trials are required to determine the effects of SPMs in humans. This review integrates the currently available knowledge of the therapeutic impact of SPMs in CVD from preclinical and clinical studies, along with the implicated molecular pathways. In vitro results have been promising, and as such, SPMs could soon represent a new therapeutic alternative for CVD.

Resolution-Based Therapies: The Potential of Lipoxins to Treat Human Diseases

Inflammation is an a physiological response instead an essential response of the organism to injury and its adequate resolution is essential to restore homeostasis. However, defective resolution can be the precursor of severe forms of chronic inflammation and fibrosis. Nowadays, it is known that an excessive inflammatory response underlies the most prevalent human pathologies worldwide. Therefore, great biomedical research efforts have been driven toward discovering new strategies to promote the resolution of inflammation with fewer side-effects and more specificity than the available anti-inflammatory treatments. In this line, the use of endogenous specialized pro-resolving mediators (SPMs) has gained a prominent interest. Among the different SPMs described, lipoxins stand out as one of the most studied and their deficiency has been widely associated with a wide range of pathologies. In this review, we examined the current knowledge on the therapeutic potential of lipoxins to treat diseases characterized by a severe inflammatory background affecting main physiological systems, paying special attention to the signaling pathways involved. Altogether, we provide an updated overview of the evidence suggesting that increasing endogenously generated lipoxins may emerge as a new therapeutic approach to prevent and treat many of the most prevalent diseases underpinned by an increased inflammatory response.

The Role of Arachidonic Acid Metabolism in Myocardial Ischemia-Reperfusion Injury

Patients with myocardial ischemic diseases or who are undergoing one of various heart treatments, such as open heart surgery, coronary artery bypass grafting, percutaneous coronary artery intervention or drug thrombolysis, face myocardial ischemia-reperfusion injury (MIRI). However, no effective treatment is currently available for MIRI. To improve the prognosis of people with cardiovascular disease, it is important to research the mechanism of MIRI. Arachidonic acid (AA) is one of the focuses of current research. The various metabolic pathways of AA are closely related to the development of cardiovascular disease, and the roles of various metabolites in ischemia-reperfusion injury have gradually been confirmed. AA is mainly metabolized in the cyclooxygenase (COX) pathway, lipoxygenase (LOX) pathway, and cytochrome P450 monooxygenase (CYP) pathway. This paper summarizes the progress of research on these three major AA metabolic pathways with respect to MIRI.

Pretreatment of Tribulus terrestris L. causes anti-ischemic cardioprotection through MAPK mediated anti-apoptotic pathway in rat

The aim of the present investigation is the evaluation and elucidation of the mechanisms by which Tribulus terrestris L. methanol extract (TTM) devoid of fruit exhibits protection against cardiac ischemia in in vitro (H9c2 cell line) and in vivo (Wistar rat) model. Tribulus terrestris L. (TT) was used in this study to evaluate the efficacy against cardiac ischemia employing in vitro and in vivo models of myocardial ischemia. H9c2 cells were used for the in vitro induction of ischemia. Male Wistar rats (10 weeks old) weighing 180-220 g were used for the in vivo experiments. ECG and clinically relevant cardiac biomarkers like serum lactate dehydrogenase, serum creatinine kinase, serum creatinine kinase myocardial B fraction, serum glutamic oxaloacetic transaminase and serum glutamic pyruvic transaminase were analysed to evaluate efficacy in the rat. For elucidation of molecular mechanisms of its beneficial activity in vitro, expression of apoptotic markers like Bax, Bad, Bcl-2 and signalling pathways involving mitogen-activated protein kinases like p38α, JNK, and Akt were studied. Tribulus terrestris L. was found effective against cardiac ischemia in the rat which was evident from ECG and various cardiac biomarkers analysis. Tribulus terrestris L. was found to act through the mitogen-activated signalling pathway leading to prevention of apoptosis during ischemic insult. The beneficial effect of Tribulus terrestris L. against cardiac ischemia was seen both in in vitro and in vivo models via its anti-apoptotic potential.

Fluvastatin inhibits cardiomyocyte apoptosis after myocardial infarction through Toll pathway

The present study intended to investigate the effect of fluvastatin on cardiomyocyte apoptosis after myocardial infarction in rats. Eighty myocardial infarction rat models were established and randomly divided into 4 groups (n=20): experimental group (n=20) was given fluvastatin treatment; sham operation group (n=20) and normal control group (n=20) were given saline. The dose of fluvastatin was 20 mg/(kg·d), and irrigation gavage was given for 1 week. Western blot analysis and reverse transcription-quantitative PCR (RT-qPCR) were used to detect the expression of TLR4 mRNA and protein in cardiomyocytes. TUNEL method was used to detect the apoptosis of cardiomyocytes. After fluvastatin treatment for 1 week, RT-qPCR found that compared with myocardial infarction group, the TLR4 mRNA expression of fluvastatin treatment group and normal control group was significantly increased, and the differences between groups were a statistically significant difference (P<0.05). Western blot analysis showed that compared with the myocardial infarction group, the expression of TLR4 protein in normal control group, sham operation group and fluvastatin treatment group were significantly decreased, and they all were statistically significant (P<0.05). TUNEL method found that compared with the myocardial infarction group, the fluvastatin treatment group could significantly reduce the apoptosis of cardiomyocytes (19.2±3.8%), and the difference was statistically significant (P<0.05). Fluvastatin can inhibit myocardial infarction and decrease cardiomyocyte apoptosis by increasing the expression of TLR4-like receptor.

Cardioprotective time-window of Penehyclidine hydrochloride postconditioning: A rat study

Pharmacological postconditioning offers a clinical perspective for all patients with ischemic heart disease. Penehyclidine hydrochloride (PHC) is a new type of anticholinergic drug. We previously reported that PHC preconditioning protects against I/R injury in rat hearts in vivo. Ischemic heart disease often occurs suddenly, so postconditioning is more significant than preconditioning. However, studies evaluating myocardial protective effects of PHC postconditioning are unavailable. We explored the effects and time-window of cardioprotection of PHC postconditioning in myocardial I/R injury. PHC was administered by intravenous at various times (t = -5, 0, 5, 10, 15, or 30min) after the onset of reperfusion in addition to I/R rat. We observed five different indicators including infarct size, inflammatory response, myocardial enzyme, oxidative stress, and Ca²⁺ overload to quantify the effect of cardioprotection. Evans blue and TTC staining were used to measure myocardial infarct size. The expression of NF-κ B and IκB-α was analyzed using Western blot. ELISA was conducted to detect inflammatory and anti-inflammatory mediators. The Ca²⁺ level was determined using assay kit. PHC postconditioning (from -5 to 10min after the onset of reperfusion) significantly reduced infarct size, downregulated NF-κ B expression, and decreased the release of inflammatory mediators, while significantly upregulating IκB-α expression and increasing the release of anti-inflammatory mediators. All PHC postconditioning groups significantly reduced Ca²⁺ level. PHC postconditioning is cardioprotective over a larger time-window (from -5 to 10min after the onset of reperfusion). The probable mechanism is inhibition of NF-кB regulated inflammatory response pathway.

Regulation of inflammation by lipid mediators in oral diseases

Lipid mediators (LM) of inflammation are a class of compounds derived from ω-3 and ω-6 fatty acids that play a wide role in modulating inflammatory responses. Some LM possess pro-inflammatory properties, while others possess proresolving characteristics, and the class switch from pro-inflammatory to proresolving is crucial for tissue homeostasis. In this article, we review the major classes of LM, focusing on their biosynthesis and signaling pathways, and their role in systemic and, especially, oral health and disease. We discuss the detection of these LM in various body fluids, focusing on diagnostic and therapeutic applications. We also present data showing gender-related differences in salivary LM levels in healthy controls, leading to a hypothesis on the etiology of inflammatory diseases, particularly Sjögren's syndrome. We conclude by enumerating open areas of research where further investigation of LM is likely to result in therapeutic and diagnostic advances.

Effect of Alox-15 Polymorphism on GCF Levels of Lipoxin-A4 in Chronic Periodontitis: A Preliminary Study

Lipoxins play an important role in periodontal resolution, hence, investigation of genetic polymorphism of lipoxin gene may provide important information on the role of lipoxins in periodontal disease pathogenesis. The aim of this study was to investigate a polymorphism of C-to-T substitution at position c.-292 in ALOX15 (reticulocyte-type 15 lipoxygenase 1) gene in patients with chronic periodontitis and to associate the polymorphism with gingival crevicular fluid (GCF) lipoxin A4 (LXA4) levels. Forty-five chronic periodontitis and 45 periodontally healthy patients were included in this case-control study. Plaque index, calculus index, sulcus bleeding index, full mouth probing depth (PD) and clinical attachment loss (CAL) were recorded. GCF and blood samples were collected. GCF was analyzed for LXA4 levels by enzyme linked immunosorbant assay. Genotyping of ALOX15 polymorphism was studied using PCR. Mean LXA4 was lower in periodontitis group compared to the periodontally healthy group. There was a negative correlation between CAL and LXA4. The CC genotype was higher in the study group than in the control group. In the study group, mean CAL was significantly lower among individuals with the CT genotype. Mean LXA4 was significantly lower in CC genotype (45.0±7.11 ng/mL) compared to CT genotype (50.81±5.81 ng/mL) among the patients with periodontitis. The results suggest that LXA4 and c.-292T allele are associated with periodontal health. Polymorphisms in the ALOX15 gene may influence periodontal disease pathogenesis. Hence, investigation of such polymorphisms could benefit the evaluation of lipoxins role in periodontal disease.

Diabetic macular edema, retinopathy and age-related macular degeneration as inflammatory conditions

Diabetic macular edema (DME) and diabetic retinopathy (DR) are complications affecting about 25% of all patients with long-standing type 1 and type 2 diabetes mellitus and are a major cause of significant decrease in vision and quality of life. Age-related macular degeneration (AMD) is not uncommon, and diabetes mellitus affects the incidence and progression of AMD through altering hemodynamics, increasing oxidative stress, accumulating advanced glycation end products, etc. Recent studies suggest that DME, DR and AMD are inflammatory conditions characterized by a breakdown of the blood-retinal barrier, inflammatory processes and an increase in vascular permeability. Key factors that seem to have a dominant role in DME, DR and AMD are angiotensin II, prostaglandins and the vascular endothelial growth factor and a deficiency of anti-inflammatory bioactive lipids. The imbalance between pro- and anti-inflammatory eicosanoids and enhanced production of pro-angiogenic factors may initiate the onset and progression of DME, DR and AMD. This implies that bioactive lipids that possess anti-inflammatory actions and suppress the production of angiogenic factors could be employed in the prevention and management of DME, DR and AMD.

Lipoxin A4 Preconditioning Attenuates Intestinal Ischemia Reperfusion Injury through Keap1/Nrf2 Pathway in a Lipoxin A4 Receptor Independent Manner

Oxidative stress plays a critical role in the pathogenesis of intestinal ischemia reperfusion (IIR) injury. Enhancement in endogenous Lipoxin A4 (LXA4), a potent antioxidant and mediator, is associated with attenuation of IIR. However, the effects of LXA4 on IIR injury and the potential mechanisms are unknown. In a rat IIR (ischemia 45 minutes and subsequent reperfusion 6 hours) model, IIR caused intestinal injury, evidenced by increased serum diamine oxidase, D-lactic acid, intestinal-type fatty acid-binding protein, and the oxidative stress marker 15-F2t-Isoprostane. LXA4 treatment significantly attenuated IIR injury by reducing mucosal 15-F2t-Isoprostane and elevating endogenous antioxidant superoxide dismutase activity, accompanied with Keap1/Nrf2 pathway activation. Meanwhile, LXA4 receptor antagonist Boc-2 reversed the protective effects of LXA4 on intestinal injury but failed to affect the oxidative stress and the related Nrf2 pathway. Furthermore, Nrf2 antagonist brusatol reversed the antioxidant effects conferred by LXA4 and led to exacerbation of intestinal epithelium cells oxidative stress and apoptosis, finally resulting in a decrease of survival rate of rat. Meanwhile, LXA4 pretreatment upregulated nuclear Nrf2 level and reduced hypoxia/reoxygenation-induced IEC-6 cell damage and Nrf2 siRNA reversed this protective effect of LXA4 in vitro. In conclusion, these findings suggest that LXA4 ameliorates IIR injury by activating Keap1/Nrf2 pathway in a LXA4 receptor independent manner.

Anti-inflammatory properties of lipoxin A4 protect against diabetes mellitus complicated by focal cerebral ischemia/reperfusion injury

Lipoxin A4 can alleviate cerebral ischemia/reperfusion injury by reducing the inflammatory reaction, but it is currently unclear whether it has a protective effect on diabetes mellitus complicated by focal cerebral ischemia/reperfusion injury. In this study, we established rat models of diabetes mellitus using an intraperitoneal injection of streptozotocin. We then induced focal cerebral ischemia/reperfusion injury by occlusion of the middle cerebral artery for 2 hours and reperfusion for 24 hours. After administration of lipoxin A4 via the lateral ventricle, infarction volume was reduced, the expression levels of pro-inflammatory factors tumor necrosis factor alpha and nuclear factor-kappa B in the cerebral cortex were decreased, and neurological functioning was improved. These findings suggest that lipoxin A4 has strong neuroprotective effects in diabetes mellitus complicated by focal cerebral ischemia/reperfusion injury and that the underlying mechanism is related to the anti-inflammatory action of lipoxin A4.

Decreased plasma levels of lipoxin A4 in children with autism spectrum disorders

The aim of this study was to evaluate the plasma levels of lipoxin A4 (LXA4), a mediator involved in the resolution of inflammation in Chinese children with autism spectrum disorders (ASD). From January 2013 to June 2014, a total of 150 children (75 confirmed ASD cases and 75 their age-matched and sex-matched control cases) participated in this study after consent was obtained from their parents. Clinical information was collected. Plasma levels of LXA4 were measured at baseline. The severity of ASD was assessed at admission using the Childhood Autism Rating Scale total score. The results indicated that the mean plasma levels of LXA4 were significantly lower in autistic children compared with the normal children (P<0.0001). There was a significant negative relationship between circulating LXA4 levels and severity of autism evaluated by Childhood Autism Rating Scale scores (P=0.006) after adjustment for the possible covariates. On the basis of the receiver operating characteristic curve, the optimal cutoff value of plasma LXA4 levels as an indicator for an auxiliary diagnosis of ASD was projected to be 81.5 pg/ml, which yielded a sensitivity of 90.7% and a specificity of 76.0%, with the area under the curve at 0.911 (95% confidence interval, 0.867-0.955). These results suggested that autistic children had lower plasma LXA4 levels, suggesting an increased susceptibility to recurring inflammation in these samples.

Ginseng total saponin attenuates myocardial injury via anti-oxidative and anti-inflammatory properties

Background

Ginseng total saponin (GTS) contains various ginsenosides. These ginsenosides are widely used for treating cardiovascular diseases in Asian communities. The aim of this study was to study the effects of GTS on cardiac injury after global ischemia and reperfusion (I/R) in isolated guinea pig hearts.

Methods

Animals were subjected to normothermic ischemia for 60 minutes, followed by 120 minutes of reperfusion. GTS significantly increased aortic flow, coronary flow, and cardiac output. Moreover, GTS significantly increased left ventricular systolic pressure and the maximal rate of contraction (+dP/dt_max) and relaxation (−dP/dt_max). In addition, GTS has been shown to ameliorate electrocardiographic changes such as the QRS complex, QT interval, and RR interval.

Results

GTS significantly suppressed the biochemical parameters (i.e., lactate dehydrogenase, creatine kinase-MB fraction, and cardiac troponin I levels) and normalized the oxidative stress markers (i.e., malondialdehyde, glutathione, and nitrite). In addition, GTS also markedly inhibits the expression of interleukin-1β (IL-1β), IL-6, and nuclear factor-κB, and improves the expression of IL-10 in cardiac tissue.

Conclusion

These data indicate that GTS mitigates myocardial damage by modulating the biochemical and oxidative stress related to cardiac I/R injury.

Protective effects of lipoxin A4 in testis injury following testicular torsion and detorsion in rats

Purpose. To investigate the protective effects of lipoxin A4 (LXA4) in rat testis injury following testicular torsion/detorsion. Methods. A rat testicular torsion model has been established as described. Rats were randomly divided into 6 groups: sham group, torsion group, torsion/detorsion (T/D) group, and T/D plus LXA4-pretreated groups (3 subgroups). Rats in LXA4-pretreated groups received LXA4 injection (0.1, 1.0, and 10 μg/kg body weight in LXA4-pretreated subgroups 1–3, resp.) at a single dose 1 h before detorsion. Biochemical analysis, apoptosis assessment, and morphologic evaluation were carried out after orchiectomies. Results. GPx and SOD levels significantly increased and MDA levels significantly reduced in LXA4-pretreated groups compared to T/D group. LXA4 also reverted IL-2 and TNF-α to basal levels and improved the expression of IL-4 and IL-10 in LXA4-pretreated groups. Moreover, the expression of NF-κB was downregulated in LXA4-pretreated groups. LXA4 treatment also showed an improved testicular morphology and decreased apoptosis in testes. Conclusion. Lipoxin A4 protects rats against testes injury after torsion/detorsion via modulation of cytokines, oxidative stress, and NF-κB activity.

Lipoxin a4 preconditioning and postconditioning protect myocardial ischemia/reperfusion injury in rats

This study aims to investigate the pre- and postconditioning effects of lipoxin A₄ (LXA₄) on myocardial damage caused by ischemia/reperfusion (I/R) injury. Seventy-two rats were divided into 6 groups: sham groups (C₁ and C₂), I/R groups (I/R₁ and I/R₂), and I/R plus LXA₄ preconditioning and postconditioning groups (LX₁ and LX₂). The serum levels of IL-1β, IL-6, IL-8, IL-10, TNF-α, and cardiac troponin I (cTnI) were measured. The content and the activity of Na⁺-K⁺-ATPase as well as the superoxide dismutase (SOD), and malondialdehyde (MDA) levels were determined. Along with the examination of myocardium ultrastructure and ventricular arrhythmia scores (VAS), connexin 43 (Cx43) expression were also detected. Lower levels of IL-1β, IL-6, IL-8, TNF-α, cTnI, MDA content, and VAS and higher levels of IL-10, SOD activity, Na⁺-K⁺-ATPase content and activity, and Cx43 expression appeared in LX groups than I/R groups. Besides, H&E staining, TEM examination as well as analysis of gene, and protein confirmed that LXA₄ preconditioning was more effective than postconditioning in preventing arrhythmogenesis via the upregulation of Cx43. That is, LXA₄ postconditioning had better protective effect on Na⁺-K⁺-ATPase and myocardial ultrastructure.

Lipoxin A4-induced heme oxygenase-1 protects cardiomyocytes against hypoxia/reoxygenation injury via p38 MAPK activation and Nrf2/ARE complex

OBJECTIVE

To investigate whether lipoxin A4 (LXA4) increases expression of heme oxygenase-1(HO-1) in cardiomyocytes, whether LXA4-induced HO-1 protects cardiomyocytes against hypoxia/reoxygenation (H/R) injury, and what are the mechanisms involved in the LXA4-induced HO-1 induction.

METHODS

Rat cardiomyocytes were exposed to H/R injury with or without preincubation with LXA4 or HO-1 inhibitor ZnPP-IX or various signal molecule inhibitors. Expressions of HO-1 protein and mRNA were analyzed by using Western blot and RT-PCR respectively. Activity of nuclear factor E2-related factor 2 (Nrf2) binding to the HO-1 E1 enhancer was assessed by chromatin immunoprecipitation. Nrf2 binding to the HO-1 antioxidant responsive element (ARE) were measured by using electrophoretic mobility shift assay.

RESULTS

Pretreatment of the cells undergoing H/R lesion with LXA4 significantly reduced the lactate dehydrogenase and creatine kinase productions, increased the cell viability, and increased the expressions of HO-1 protein and mRNA and HO-1 promoter activity. HO-1 inhibition abolished the protective role of LXA4 on the cells undergoing H/R lesion. LXA4 increased p38 mitogen-activated protein kinase (p38 MAPK) activation, nuclear translocation of Nrf2, Nrf2 binding to the HO-1 ARE and E1 enhancer in cardiomyocytes with or without H/R exposure.

CONCLUSION

The protection role of LXA4 against H/R injury of cardiomyocytes is related to upregulation of HO-1, via activation of p38 MAPK pathway and nuclear translocation of Nrf2 and Nrf2 binding to the HO-1 ARE and E1 enhancer, but not via activation of phosphatidyinositol-3-kinase or extracellular signal-regulated kinase pathway.

Involvement of K+ channel-dependant pathways in lipoxin A4-induced protective effects on hypoxia/reoxygenation injury of cardiomyocytes

Studies have shown that lipoxin A4 (LXA4) and activation of LXA4 receptor provided protection against myocardial ischemia/reperfusion injury in animal models. However, the mechanisms by which LXA4 induced protective role on myocardial ischemia/reperfusion injury remains unclear. In the present studies, we investigated the protective effects of LXA4 on H9c2 cardiomyocytes exposed to hypoxia/reoxygenation (H/R) injury and involvement of heme oxygenase-1 (HO-1)- and K(+) channel-dependant pathways in the LXA4 action. H9c2 cardiomyocytes were pretreated with or without LXA4 or HO-1 specific interfering RNA (siRNA) or various blockers and openers of K(+) channels before exposing to H/R injury. The levels of lactate dehydrogenase (LDH) and creatine kinase (CK) in cellular supernatants and necrosis factor-α (TNF-α) in cellular lysates were measured by using ELISA. Expressions of HO-1 mRNA and protein were analyzed by using RT-PCR and Western blot respectively. Pretreatment of the cells undergoing H/R injury with LXA4 significantly reduced the LDH and CK levels induced by H/R injury, and increased the expressions and activity of HO-1. However, the protective effects of LXA4 were completely blocked by transfection of the cells with HO-1 siRNA, and were partially but significantly blocked by pretreatment of the cells with various blockers of K(+) channels. The LXA4-induced expressions of HO-1 in the cells were also inhibited by HO-1 siRNA and various blockers of K(+) channels. The inhibitory effects of LXA4 on enhanced TNF-α levels induced by H/R injury were abolished by transfection of the cells with HO-1 siRNA. In conclusion, the protective role of LXA4 on cardiomyocytes against H/R injury is related to upregulation of HO-1 via reduced production of TNF-α and activation of ATP-sensitive K(+) channels and calcium-sensitive K(+) channel.