Essential fatty acid deficiency inhibits the in vivo generation of leukotriene B4 and suppresses levels of resident and elicited leukocytes in acute inflammation

Essential fatty acid (EFA) deficiency exerts an anti-inflammatory effect in several models of inflammation. In an effort to understand underlying mechanisms, the effect of EFA deficiency on the generation of eicosanoids and the elicitation of leukocytes in a model of acute inflammation was examined. Acute inflammation was induced by the i.p. injection of zymosan in mice. The injection of zymosan in normal mice was followed by a short burst of eicosanoid synthesis lasting 2 hr. Leukotriene (LT)B4, LTC4, LTD4, and LTE4, thromboxane B2, and 6-keto-prostaglandin F1 alpha were detected using high pressure liquid chromatography and specific radioimmunoassays. This initial phase of eicosanoid production was followed by a more prolonged infiltration of leukocytes (predominantly polymorphonuclear neutrophils (PMN)) lasting 48 hr with little eicosanoid synthesis. When challenged with zymosan, EFA-deficient mice exhibited a marked decrease in the production of eicosanoids during the early phase. No LTB could be detected at all. The number of resident peritoneal macrophages in EFA-deficient mice was also substantially decreased, and the influx of PMN during the inflammatory response was markedly diminished. In order to establish that the generation of eicosanoids during the early phase of this model of acute inflammation played a causal role in the later infiltration of PMN, the effect of the mixed lipoxygenase/cyclooxygenase inhibitor, BW755C, on LTB formation and PMN influx in this model of inflammation was assessed in control animals. BW755C completely blocked LTB synthesis and inhibited the subsequent influx of PMN. In conclusion, EFA deficiency inhibits eicosanoid generation, depresses levels of resident macrophages, and markedly diminishes the influx of PMN in the acute inflammatory response. The decrease in PMN influx appears to result from the inhibition of the antecedent generation of LTB.     

Neutrophil-mediated accumulation of 2-ClHDA during myocardial infarction: 2-ClHDA-mediated myocardial injury

The pathophysiological sequelae of myocardial infarction include neutrophil infiltration into the infarct zone that contributes to additional damage to viable tissue and removal of cellular debris from necrosed tissue. Reactive chlorinating species produced by myeloperoxidase amplify the oxidant capacity of activated neutrophils. Plasmalogens are a major phospholipid subclass of both endothelial cells and cardiac myocytes. Recent studies have shown that plasmalogens are targeted by neutrophil-derived reactive chlorinating species that lead to the production of alpha-chloro fatty aldehydes. Results herein demonstrate that the alpha-chloro fatty aldehyde 2-chlorohexadecanal (2-ClHDA) accumulates in rat hearts subjected to left anterior descending coronary artery occlusion. Myocardia from rats subjected to surgical infarction had increased 2-ClHDA and neutrophil infiltration levels compared with myocardia from rats subjected to sham surgery. Additionally, infarcted myocardia from rats rendered neutropenic by treatments with an anti-neutrophil antibody had diminished 2-ClHDA and neutrophil infiltration levels compared with infarcted myocardia from normopenic rats; 2-ClHDA was shown to elicit myocardial damage as determined by lactate dehydrogenase release in isolated perfused rat hearts. Additionally, 2-ClHDA treatment of hearts resulted in decreased heart rate and ventricular performance. Taken together, the present results demonstrate a novel neutrophil-dependent myeloperoxidase-based mechanism that results in 2-ClHDA production in response to regional myocardial infarction that may also contribute to cardiac dysfunction.     

In vivo labeling studies on the biosynthesis and degradation of collagen in experimental myocardial infarction.

The biosynthesis and degradation of myocardial collagen was studied in myocardium infarcted rats after a single intraperitoneal injection of 3H-proline. The incorporation of tritiated proline into collagen as 3H-hydroxyproline was regarded as a measure of collagen synthesis. The total content as well as total activity of hydroxyproline were measured in the whole homogenate, neutral salt soluble fraction, insoluble fraction and in urine collected at different time intervals and specific activities were calculated. Both collagen anabolism and catabolism were found to be affected in infarcted rat hearts. Degradation of existing collagen at the earlier stages of myocardial infarction and a simultaneous new collagen synthesis and deposition as insoluble form later took place.     

Discrimination of Recent Ischemic Myocardial Changes in WHHLMI Rabbits from the Findings of Postmortem Degeneration.

To distinguish recent ischemic myocardial changes in myocardial infarction-prone Watanabe heritable hyperlipidemic (WHHLMI) rabbits from general postmortem myocardial degeneration, we examined hearts of WHHLMI rabbits after sudden death and postmortem hearts of non-atherogenic rabbits. Hearts of 8 WHHLMI rabbits were excised within 30 min of sudden death and hearts of 27 non-atherosclerotic rabbits were excised at designated periods after sacrifice. A large number of myocardial cells from WHHLMI rabbits exhibited features characteristic of ischemia (intercellular gap, intracellular edema, eosinophilia, disappearance of myocardial cells, indistinct nuclei, wavy myocardial fibers) simultaneously at regions close to proximal occluded coronary arteries. Although postmortem hearts of non-atherosclerotic rabbits exhibited similar characteristics, several features characteristic of autolyzed myocytes were also randomly observed in the left ventricle wall. Each feature was detected independently in myocardial cells or regions of the ventricle wall. In conclusion, we found several unique characteristics associated with myocardial infarction which enable discrimination between recent ischemic myocardial changes and myocardial degeneration following death.     

Label‐free imaging of healthy and infarcted fetal sheep hearts by two‐photon microscopy

Coronary heart disease is one of the largest causes of death worldwide, making this a significant health care issue. A critical problem for the adult human heart is that it does not undergo effective repair in response to damage, leaving patients with a poor prognosis. Unlike the adult, fetal hearts have the ability to repair after myocardial damage. Using two‐photon microscopy, we have visualised the morphological and metabolic changes following myocardial infarction in sheep fetuses, to characterise response to cardiac injury in a mammalian model. Following myocardial infarction, fetal hearts showed no significant increase in collagen deposition in the region of the infarction, when compared to either the surrounding tissue or shams. In contrast, metabolic activity (i. e. NAD(P)H and FAD) was significantly reduced in the region of myocardial infarction, when compared to either the surrounding tissue or sham hearts. For comparison, we also imaged two hearts from preadolescent sheep (sham and myocardial infarction) and showed highly ordered collagen deposition with decreased metabolic activity within the infarcted area. Therefore, two‐photon imaging had the capacity to image both morphological and metabolic changes in response to myocardial infarction and showed differences in the response with age. Picture : Two‐photon imaging of myocardial infarction ( b and d ) enabled the visualisation of increased collagen (blue; Em=431 nm) and changes in other tissue autofluorescence (green; Em=489–606 nm) in fetal ( a and b ) and preadolescent ( c and d ) hearts, compared to shams ( a and c ). The excitation wavelength was 840 nm. Scale bars: 10 μm.

     

The antiinflammatory effects of essential fatty acid deficiency in experimental glomerulonephritis. The modulation of macrophage migration and eicosanoid metabolism

Dietary polyunsaturated fatty acid modulation exerts a beneficial effect in immune-mediated glomerulonephritis. To elucidate the mechanisms underlying this phenomenon, the effects of essential fatty acid (EFA) deficiency on the heterologous phase of nephrotoxic nephritis in rats (induced by the injection of a rabbit antiglomerular basement membrane antibody) were studied. The heterologous phase of nephrotoxic nephritis was characterized by an invasion of leukocytes into the glomerulus. Polymorphonuclear neutrophils predominated early on (3 h), whereas macrophages predominated at 24 and 72 h. EFA deficiency selectively prevented the influx of macrophages into the glomerulus. The invasion of polymorphonuclear neutrophils, in contrast, was unaffected. The influx of leukocytes into the glomerulus during nephritis was accompanied by a marked enhancement (10- to 40-fold) in glomerular thromboxane and leukotriene B4 production. EFA deficiency largely attenuated this change. Renal dysfunction during the heterologous phase of nephritis was manifested as azotemia, polyuria, sodium retention, and proteinuria. With EFA deficiency, polyuria, azotemia, and sodium retention were not seen. Proteinuria was reduced by approximately 85%. To address whether the lack of macrophage migration into the glomerulus in the context of nephritis with EFA deficiency might be due to a functional defect in macrophage migration, the chemotactic responsiveness of EFA-deficient macrophages was examined. EFA-deficient macrophages displayed normal chemotactic migration toward activated C. In sum, EFA deficiency prevents the invasion of macrophages into the glomerulus in nephrotoxic nephritis and attenuates the accompanying metabolic and functional alterations, but does not affect macrophage chemotactic responsiveness. Alterations in macrophage elicitation and lipid mediator generation by inflamed glomeruli thus appear to be central to the salutary effect of dietary polyunsaturated fatty acid modification on glomerulonephritis.     

Effect of simvastatin on collagen I deposition in non-infarcted myocardium: role of NF-κB and osteopontin

The novel biological effect of statins in alleviating myocardium fibrosis following infarction has been increasingly recognized, yet the underlying mechanisms are not fully understood. The purpose of this study was to characterize the effect of simvastatin on myocardial fibrosis and collagen I deposition in the non-infarcted region after myocardial infarction (MI) and to identify the role of NF-κB and osteopontin in simvastatin-mediated inhibition of post-MI collagen over-expression. A rat model of MI was generated by ligating the left anterior descending coronary artery. The rats surviving the MI operation were randomly divided into the following 3 groups: myocardial infarction (MI, vehicle), simvastatin (Sim, 30 mg·kg-1·day-1), and pyrrolidine dithiocarbamate (PDTC, an inhibitor of NF-κB, 100 mg·kg-1·day-1). Four weeks after MI, cardiac function, mRNAs, and protein expression in non-infarcted myocardium were analyzed. Myocardial fibrosis and collagen I over-expression were observed following MI, accompanied by an increase of NF-κB and osteopontin. Simvastatin improved post-MI left ventricular dysfunction and ameliorated post-MI associated changes to several cardiac parameters, including the left ventricular end diastolic pressure (LVEDP), the maximal rate of pressure development (+dP/dtmax), and the maximal rate of pressure decline (-dP/dtmax). Concurrently, simvastatin significantly suppressed the over-expression of NF-κB, osteopontin, and collagen I in the non-infarcted region following MI. Inhibition of NF-κB by PDTC also reduced osteopontin over-expression and excessive collagen I production and improved the above functional myocardial parameters. These results show that post-MI myocardial fibrosis and collagen I over-expression in the non-infarcted region is associated with activation of NF-κB and osteopontin up-regulation. The anti-fibrotic effect of simvastatin following MI is associated with the attenuation of the expression of osteopontin and NF-κB. The inhibition of NF-κB activation could be the process upstream of osteopontin suppression in the simvastatin-mediated effect.     

Metabolic and functional alterations in macrophages induced by essential fatty acid deficiency

Essential fatty acid (EFA) deficiency has been shown to protect against the glomerulonephritis in a murine model of systemic lupus erythematosus. Since macrophages are an important cellular constituent of the inflammatory lesion, the effects of EFA deficiency on the eicosanoid metabolism and function of these cells were determined. EFA-deficient macrophages exhibited a depletion of phospholipid arachidonate and an accumulation of 20:3(n-9); phosphatidylinositol was the phospholipid most affected. When these macrophages were stimulated with unopsonized zymosan, they produced markedly less leukotriene C4 and B4 than control macrophages. EFA-deficient macrophages also synthesized leukotriene C3 from endogenous 20:3(n-9). No leukotriene B3 was detected. In contrast to the effects on leukotriene production, prostaglandin and thromboxane production were only minimally affected by EFA deficiency. When challenged with zymosan, EFA-deficient macrophages released less arachidonate relative to control macrophages and released half again as much 20:3(n-9) as arachidonate. Release of arachidonate from phosphatidylcholine in the EFA-deficient cells was highly selective for arachidonate; however, release of arachidonate from phosphatidylinositol was depressed relative to control and was not selective. Incubation of macrophages with exogenous arachidonate and 20:3(n-9) established that 20:3(n-9) decreased leukotriene C4 and B4 synthesis from arachidonate but did not affect prostaglandin production. To determine the functional effects of the deficiency state, receptor-mediated pinocytosis and phagocytosis were also examined in EFA-deficient cells. EFA-deficient macrophages exhibited a marked reduction in receptor-mediated pinocytosis. Phagocytosis, however, was unaffected by the deficiency state. These effects on macrophage eicosanoid metabolism and function may comprise a significant component of the anti-inflammatory effect of EFA deficiency.     

Neutrophil kinetics in O2-exposed rabbits

Hyperoxic injury results in an influx of polymorphonuclear leukocytes (PMN) into the lung. To better understand the role of the PMN in this injury, kinetic studies were used to assess the survival of PMNs in the circulation. The rate of deposition of PMNs in the lungs of rabbits exposed to hyperoxia was also examined. The half-lives (T1/2) of [3H]thymidine-labeled PMNs in the circulation in rabbits exposed to air or to 95% O2 for less than or equal to 48 h varied between 3.9 and 4.5 h. After 72 h of hyperoxic exposure, T1/2 fell to 2.2 h, the marginal and circulating PMN pool increased and 3H deposition in the lung increased 10-fold. Autoradiographs confirmed that [3H]thymidine was initially nuclear- and cellular-associated but, with time, [3H]thymidine dispersed throughout the lung, suggesting PMN disintegration. These PMN events seem to occur in the later phases of O2 toxicity, and because PMNs are an additional source of oxyradicals, they may further amplify oxidant injury.     

Macrophage procoagulant-inducing factor. In vivo properties and chemotactic activity for phagocytic cells

Murine macrophage procoagulant-inducing factor (MPIF) is a lymphokine with chemical properties distinct from a number of well-characterized cytokines. MPIF induces procoagulant activity on the surface of macrophages and thus may play a central role in the expression of cell-mediated immunity. Highly enriched MPIF-alpha and -beta, separated by virtue of their basic isoelectric point and affinity for heparin, induced local induration and fibrin deposition and cellular infiltration similar to that observed in delayed type hypersensitivity reactions, when injected intradermally. Margination with of polymorphonuclear leukocytes (PMN) along the endothelium as well as increased PMN infiltration was evident after 4 h. In contrast to other inflammatory mediators (e.g., C5a, IL-1) reactivity was sustained, with greater numbers of mononuclear cells apparent 24 h after skin testing. Changes in the dermis were evident 4 h after MPIF injection with increased numbers of cells near areas where spaces in the collagen bundles had formed. Dermal thickening was evident after 24 h and collagen fiber structure was disrupted. Extravascular fibrinogen/fibrin was most prominent 24 h after testing. LPS, which induces macrophage procoagulant activity in vitro, did not induce the histopathologic changes evident with MPIF. MPIF was chemotactic for PMN and macrophages in vitro. Chemotactic activity was heat-labile and not due to C5a. Migration was dependent on a concentration gradient, as determined by checkerboard analysis, indicating that MPIF promoted chemotaxis rather than chemokinesis. Experiments reported here suggest that MPIF is an important mediator of fibrin deposition and cellular infiltration characteristic of cell-mediated immune response.     

Effect of cytokines on polymorphonuclear neutrophil infiltration in the mouse. Prostaglandin- and leukotriene-independent induction of infiltration by IL-1 and tumor necrosis factor

The i.p. injection of mice with highly purified recombinant human rIL-1 alpha or beta resulted in the rapid influx of a large number of polymorphonuclear neutrophils (PMN) into the peritoneal cavity. Significant increases in the number of PMN were induced by doses of IL-1 which ranged from 0.005 to 5 ng/injection. Interestingly the dose response for PMN influx was bell-shaped because 50 ng of IL-1 did not result in a significant increase in peritoneal PMN. IL-1 induced PMN infiltration was detectable by 1 h with peak levels of PMN obtained by about 2 h, followed by a subsequent decline by 24 h. Other cytokines, IL-2, IFN-gamma, IFN alpha beta, granulocyte-CSF, granulocyte-macrophage-CSF, IL-3, TNF-alpha, and TNF-beta were compared to IL-1 for their ability to induce a PMN influx into the peritoneum. Only TNF-alpha or TNF-beta (lymphotoxin) were able to induce a significant influx of PMN within 2 h. However, based on total protein administered, about 100 times more TNF than IL-1 was required to produce a comparable PMN infiltration. Intraperitoneal injection of inhibitors of the cyclooxygenase or lipoxygenase pathways did not inhibit the IL-1-induced influx of PMN. Also, neither IL-1 nor TNF triggered an increase in PG or leukotriene release from peritoneal cells in vitro. Furthermore, direct peritoneal injection of leukotriene B4, a potent PMN chemoattractant in vitro, did not induce any significant increase in PMN in the peritoneal cavity indicating that chemotactic activity alone is insufficient for inducing peritoneal infiltration. These results suggest that the local production of very low levels of IL-1 in vivo would be sufficient to initiate a sequence of events that results in a rapid accumulation of PMN. Because IL-1 was not chemotactic for PMN in vitro, our data suggest that IL-1 induces production of factors that are chemotactic for PMN. Alternatively, IL-1 may act on other stages of the complex sequence of events that regulates the emigration of PMN into tissue sites in vivo. The synergy apparent in PMN influx when suboptimal concentrations of IL-1 and TNF were injected suggests that the local production of very low concentrations of these cytokines in situ could play a critical role in the emigration of PMN during infection.     

The relative contribution of glucose and fatty acids to ATP production in hearts reperfused following ischemia

High levels of fatty acids decrease the extent of mechanical recovery of hearts reperfused following a transient period of severe ischemia. Glucose oxidation rates during reperfusion are low under these conditions, which can result in a decreased recovery of mechanical function. Stimulation of glucose oxidation with the carnitine palmitoyl transferase I inhibitor, Etomoxir, or by directly stimulating pyruvate dehydrogenase activity with dichloroacetate (DCA) results in an improvement in mechanical function during reperfusion of previously ischemic hearts. Addition of DCA (1 mM) to hearts perfused with 11 mM glucose and 1.2 mM palmitate results in an increase in contribution of glucose oxidation to overall ATP production from 6 to 23%, with a parallel decrease in that of fatty acid oxidation from 90 to 69%. In aerobic hearts, endogenous myocardial triglycerides are an important source of fatty acids for -oxidation. Using hearts in which the myocardial triglycerides were pre-labeled, the contribution of both endogenous and exogenous fatty acid oxidation to myocardial ATP production was determined in hearts perfused with 11 mM glucose, 1.2 mM palmitate and 500 µU/ml insulin. In hearts reperfused following a 30 min period of global no flow ischemia, 91.9% of ATP production was derived from endogenous and exogenous fatty acid oxidation, compared to 87.7% in aerobic hearts. This demonstrates that fatty acid oxidation quickly recovers following a transient period of severe ischemia. Furthermore, therapy aimed at overcoming fatty acid inhibition of glucose oxidation during reperfusion of ischemic hearts appears to be beneficial to recovery of mechanical function.     

Complement inhibition reduces injury in the type 2 diabetic heart following ischemia and reperfusion

Chronic inflammation exacerbates the cardiovascular complications of diabetes. Complement activation plays an important role in the inflammatory response and is known to be involved in ischemia-reperfusion (I/R) injury in the nondiabetic heart. The purpose of this study was to determine if increased complement deposition explains, in part, the increased severity of neutrophil-mediated I/R injury in the type 2 diabetic heart. Nondiabetic Zucker lean control (ZLC) and Zucker diabetic fatty (ZDF) rats underwent 30 min of coronary artery occlusion followed by 120 min of reperfusion. Another group of ZDF rats was treated with the complement inhibitor FUT-175 before reperfusion. Left ventricular (LV) tissue samples were stained for complement deposition and neutrophil accumulation following reperfusion. We found significantly more complement deposition in the ZDF LV compared with the ZLC (P < 0.05), and complement deposition was associated with significantly greater neutrophil accumulation. In whole blood samples taken preischemia and at 120 min reperfusion, neutrophils exhibited significantly more CD11b expression in the ZDF group compared with the ZLC group (P < 0.05). Furthermore, intracellular adhesion molecule (ICAM)-1 expression following I/R was increased significantly in ZDF hearts compared with ZLC hearts (P < 0.001). These results indicate that, in the ZDF heart, increased ICAM-1 and polymorphonuclear neutrophil (PMN) CD11b expression play a role in increasing PMN accumulation following I/R. The infarct size of the ZDF was significantly greater than ZLC (P < 0.05), and treatment with FUT-175 significantly decreased infarct size, complement deposition, and PMN accumulation in the diabetic heart. These findings indicate an exacerbated inflammatory response in the type 2 diabetic heart that contributes to the increased tissue injury observed following ischemia and reperfusion.     

Systematic Characterization of Myocardial Inflammation,Repair, and Remodeling in a Mouse Model of Reperfused Myocardial Infarction

Mouse models of myocardial infarction are essential tools for the study of cardiac injury, repair, and remodeling. Our current investigation establishes a systematic approach for quantitative evaluation of the inflammatory and reparative response, cardiac function, and geometry in a mouse model of reperfused myocardial infarction. Reperfused mouse infarcts exhibited marked induction of inflammatory cytokines that peaked after 6 hr of reperfusion. In the infarcted heart, scar contraction and chamber dilation continued for at least 28 days after reperfusion; infarct maturation was associated with marked thinning of the scar, accompanied by volume loss and rapid clearance of cellular elements. Echocardiographic measurements of end-diastolic dimensions correlated well with morphometric assessment of dilative remodeling in perfusion-fixed hearts. Hemodynamic monitoring was used to quantitatively assess systolic and diastolic function; the severity of diastolic dysfunction following myocardial infarction correlated with cardiomyocyte hypertrophy and infarct collagen content. Expression of molecular mediators of inflammation and cellular infiltration needs to be investigated during the first 72 hr, whereas assessment of dilative remodeling requires measurement of geometric parameters for at least four weeks after the acute event. Rapid initiation and resolution of the inflammatory response, accelerated scar maturation, and extensive infarct volume loss are important characteristics of infarct healing in mice.     

阿魏酸对糖尿病小鼠心肌病变的影响及其机制

目的：研究阿魏酸对高脂饮食结合小剂量链脲佐菌素（STZ）诱导的2型糖尿病小鼠心肌病变的影响,探讨其可能的作用机制。方法：雄性ICR小鼠20只,高糖高脂饮食连续6周,STZ （30 mg/kg）腹腔注射连续5d后,隔9d测空腹血糖（FBG）,超过11.1 mmol/L视为糖尿病造模成功。将此20只小鼠随机分为模型组、阿魏酸组（200 mg/kg,i.g.）,每组10只;另取10只正常小鼠为对照组;连续给药8周。末次给药后,测定FBG、称体重、全心重和左心室重,计算心脏质量指数（HMI）和左室质量指数（LVMI）;测定超氧化物歧化酶（SOD）活力、丙二醛（MDA）含量;Masson染色观察左心室纤维增生情况;免疫组化法测定心肌组织转化生长因子-β1（TGF-β1）、Ⅲ型胶原蛋白表达。结果：与模型组小鼠比较,阿魏酸组小鼠HMI、LVMI减小（（P<0.01,P<0.05）,心肌组织SOD活力升高、MDA含量下降（P<0.05）;心肌胶原纤维沉积减少,间质纤维化改善;免疫组化显示心肌组织TGF-β1和Ⅲ型胶原蛋白表达减少（P<0.01,P<0.05）。结论：阿魏酸对糖尿病小鼠心肌病变具有保护作用,可能与抗氧化及抑制TGF-β1蛋白表达,减少Ⅲ型胶原蛋白沉积有关。     

A novel reciprocal loop between microRNA-21 and TGFβRIII is involved in cardiac fibrosis

Cardiac fibrosis is characterized by aberrant proliferation of cardiac fibroblasts and exaggerated deposition of extracellular matrix (ECM) in the myocardial interstitial, and ultimately impairs cardiac function. It is still controversial whether microRNA-21 (miR-21) participates in the process of cardiac fibrosis. Our previous study confirmed that transforming growth factor beta receptor III (TGFβRIII) is a negative regulator of TGF-β pathway. Here, we aimed to decipher the relationship between miR-21 and TGFβRIII in the pathogenic process of myocardial fibrosis. We found that TGF-β1 and miR-21 were up-regulated, whereas TGFβRIII was down-regulated in the border zone of mouse hearts in response to myocardial infarction. After transfection of miR-21 into cardiac fibroblasts, TGFβRIII expression was markedly reduced and collagen content was increased. And, luciferase results confirmed that TGFβRIII was a target of miR-21. It suggests that up-regulation of miR-21 could increase the collagen content and at least in part through inhibiting TGFβRIII. Conversely, we also confirmed that overexpression of TGFβRIII could inhibit the expression of miR-21 and reduce collagen production in fibroblasts. Further studies showed that overexpression of TGFβRIII could also deactivate TGF-β1 pathway by decreasing the expression of TGF-β1 and phosphorylated-Smad3 (p-Smad3). TGF-β1 has been proven as a positive regulator of miR-21. Taken together, we found a novel reciprocal loop between miR-21 and TGFβRIII in cardiac fibrosis caused by myocardial infarction in mice, and targeting this pathway could be a new strategy for the prevention and treatment of myocardial remodeling.     

Sex differences in platelet thromboxane and arterial prostacyclin production in control and n-6 fatty acid supplemented rats

Sex differences in eicosanoid production in platelets and vessel walls have been studied in control and n-6 fatty acid supplemented rats. In platelet rich plasma (PRP) of control female rats, arachidonic acid (AA) levels in phospholipids (PL), thromboxane B₂ (TxB₂) formation following collagen stimulation and aggregatory responses to collagen were higher than in PRP of male rats. 6 keto PGF_1α release from PRP-perfused isolated aortas were the same for both sexes, but the antiaggregatory activity of the wall was higher in males than in females, in association with a greater sensitivity of male platelets to prostacyclin.The administration of n-6 fatty acid supplements increased AA level in PL, TxB₂ production and aggregation only in male platelets. Production of 6 keto PGF_1α and the antiaggregatory activity of aortic walls were reduced after dietary treatment in males, but biochemical and functional parameters were not correlated in females.The results indicate complex sex-related differences in fatty acid metabolism and eicosanoid production, and in responses to n-6 dietary fatty acids in platelets and the vascular system in the rat.     

Deficiency of Capn4 Gene Inhibits Nuclear Factor-κB (NF-κB) Protein Signaling/Inflammation and Reduces Remodeling after Myocardial Infarction

Calpain has been implicated in acute myocardial injury after myocardial infarction (MI). However, the causal relationship between calpain and post-MI myocardial remodeling has not been fully understood. This study examined whether deletion of Capn4, essential for calpain-1 and calpain-2 activities, reduces myocardial remodeling and dysfunction following MI, and if yes, whether these effects of Capn4 deletion are associated with NF-κB signaling and inflammatory responses in the MI heart. A novel mouse model with cardiomyocyte-specific deletion of Capn4 (Capn4-ko) was employed. MI was induced by left coronary artery ligation. Deficiency of Capn4 dramatically reduced the protein levels and activities of calpain-1 and calpain-2 in the Capn4-ko heart. In vivo cardiac function was relatively improved in Capn4-ko mice at 7 and 30 days after MI when compared with their wild-type littermates. Deletion of Capn4 reduced apoptosis, limited infarct expansion, prevented left ventricle dilation, and reduced mortality in Capn4-ko mice. Furthermore, cardiomyocyte cross-sectional areas and myocardial collagen deposition were significantly attenuated in Capn4-ko mice, which were accompanied by down-regulation of hypertrophic genes and profibrotic genes. These effects of Capn4 knock-out correlated with restoration of IκB protein and inhibition of NF-κB activation, leading to suppression of proinflammatory cytokine expression and inflammatory cell infiltration in the Capn4-ko heart after MI. In conclusion, deficiency of Capn4 reduces adverse myocardial remodeling and myocardial dysfunction after MI. These effects of Capn4 deletion may be mediated through prevention of IκB degradation and NF-κB activation, resulting in inhibition of inflammatory responses.