Zuyi Yuan

Peroxisome proliferation-activated receptor-γ ligands ameliorate experimental autoimmune myocarditis

BACKGROUNDnPeroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligands have been shown to ameliorate a variety of inflammatory conditions. The present study tested the hypothesis that PPAR-gamma ligands reduce experimental autoimmune myocarditis (EAM) associated with inhibition of the expansion and activation of T cells, as well as suppression of the expression of proinflammatory cytokines.nnnMETHODS AND RESULTSnEAM was induced in Lewis rats by immunization with porcine cardiac myosin. PPAR-gamma ligands, 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) 200 microg/kg/day i.p. and pioglitazone (PIO) 10 mg/kg/day orally, were administered for 3 weeks to rats with EAM. The results showed that enhanced PPAR-gamma expression was prominently stained in the nuclear and perinuclear regions of infiltrating inflammatory cells. Administration of PPAR-gamma ligands markedly reduced the severity of myocarditis, as shown by comparing the heart weight/body weight ratio, pericardial effusion scores, macroscopic scores and microscopic scores. PPAR-gamma ligands suppressed myocardial mRNA expression of inflammatory cytokines and the expression of interleukin (IL)-1beta protein in rats with EAM. In addition, 15d-PGJ(2) and PIO treatment suppressed the proliferative response and interferon-gamma production of T cell-enriched splenocytes from rats with EAM. Furthermore, the cytotoxic activity and myocardiogenic potential of these T cells were inhibited by 15d-PGJ(2) treatment.nnnCONCLUSIONSnPPAR-gamma may play a role in the pathophysiology of EAM. PPAR-gamma ligands ameliorate the EAM associated with suppression of the expansion and activation of myocardiogenic T cells, as well as inhibition of the expression of proinflammatory cytokines. These results suggest that PPAR-gamma ligands such as 15d-PGJ(2) and PIO may have the potential to modulate human inflammatory heart diseases such as myocarditis.

High Glucose Promotes Intracellular Lipid Accumulation in Vascular Smooth Muscle Cells by Impairing Cholesterol Influx and Efflux Balance

AIMSnHigh glucose promotes macrophage-derived foam cell formation involved in increased influx or reduced efflux of lipids. The aim of this study is to investigate the influence of hyperglycaemia on foam cell transformation of vascular smooth muscle cells (VSMCs) and possible mechanisms contributing to these effects.nnnMETHODS AND RESULTSnThe results showed that high glucose increased the expression of CD36, a regulator of lipid influx, and suppressed the expression and activity of the adenosine triphosphate-binding cassette (ABC) transporter ABCG1, a regulator of cholesterol efflux to high-density lipoprotein, in a dose- and time-dependent manner. However, cholesterol efflux to lipid-free apoAI was not impaired. VSMCs exposed to high glucose readily developed into lipid-loaded cells, as demonstrated by Oil Red O staining and cholesterol content analysis. In addition, high glucose-induced down-regulation of ABCG1 was reversed by nuclear factor-kappaB (NF-kappaB) inhibitors BAY 11-7085 and tosyl-phenylalanine chloromethyl ketone and by the antioxidant N-acetyl-L-cysteine (NAC). This reversal was accompanied by reduced cellular lipid content. Also, NAC and NF-kappaB inhibitors can effectively block the high glucose-induced activity of NF-kappaB binding to DNA and/or peroxide production.nnnCONCLUSIONnThese results suggested that hyperglycaemia-induced foam cell formation in VSMCs was related to the imbalanced lipid flux by increasing CD36-mediated modified low-density lipoprotein uptake and reducing ABCG1-regulated cellular cholesterol efflux. Moreover, this effect was associated with increased oxidative stress and activated NF-kappaB pathway signalling.

Cardioprotection from oxidative stress in the newborn heart by activation of PPARγ is mediated by catalase

Regulation of catalase (CAT) by peroxisome proliferator-activated receptor-γ (PPARγ) was investigated to determine if PPARγ activation provides cardioprotection from oxidative stress caused by hydrogen peroxide (H(2)O(2)) in an age-dependent manner. Left ventricular developed pressure (LVDP) was measured in Langendorff perfused newborn or adult rabbit hearts, exposed to 200μM H(2)O(2), with perfusion of rosiglitazone (RGZ) or pioglitazone (PGZ), PPARγ agonists. We found: (1) H(2)O(2) significantly decreased sarcomere shortening in newborn ventricular cells but not in adult cells. Lactate dehydrogenase (LDH) release occurred earlier in newborn than in adult heart, which may be due, in part, to the lower expression of CAT in newborn heart. (2) RGZ increased CAT mRNA and protein as well as activity in newborn but not in adult heart. GW9662 (PPARγ blocker) eliminated the increased CAT mRNA by RGZ. (3) In newborn heart, RGZ and PGZ treatment inhibited release of LDH in response to H(2)O(2) compared to H(2)O(2) alone. GW9662 decreased this inhibition. (4) LVDP was significantly higher in both RGZ+H(2)O(2) and PGZ+H(2)O(2) groups than in the H(2)O(2) group. Block of PPARγ abolished this effect. In contrast, there was no effect of RGZ in adult. (5) The cardioprotective effects of RGZ were abolished by inhibition of CAT. In conclusion, PPARγ activation is cardioprotective to H(2)O(2)-induced stress in the newborn heart by upregulation of catalase. These data suggest that PPARγ activation may be an effective therapy for the young cardiac patient.

Temocapril treatment ameliorates autoimmune myocarditis associated with enhanced cardiomyocyte thioredoxin expression

Thioredoxin (TRX) is a redox regulatory protein that protects cells from various stresses. Angiotensin-converting enzyme (ACE) inhibitor was reported to enhance endogenous antioxidant enzyme activities. This study was carried out to investigate whether temocapril, a novel non-sulfhydryl containing ACE inhibitor, reduces the severity of myocarditis via redox regulation mechanisms involving TRX. Western blot showed that temocapril enhanced cytosolic redox regulatory protein TRX expression, but neither mitochondrial TRX2 nor antioxidant enzymes, such as copper-zinc superoxide dismutase (Cu/Zn-SOD) or manganese superoxide dismutase (Mn-SOD) expression, was increased by the preconditioning treatment. In rats with experimental autoimmune myocarditis (EAM), the protein carbonyl content, a marker of cellular protein oxidation, was increased accompanied with enhanced TRX expression. An immunohistochemical study showed that TRX stain was enhanced in infiltrating inflammatory cells and in damaged myocytes. The severity of the myocarditis and the protein carbonyl contents were less increased in temocapril treatment (10 mg/kg/day, orally) from day 1 to day 21 in which TRX was up regulated when the inflammation started, but not in temocapril treatment from day 15-21 in which TRX was not up-regulated when the inflammation started. The results suggest that TRX and the redox state modified by TRX may play a crucial role in the pathophysiology of EAM. Temocapril ameliorates myocarditis associated with inducing TRX increase in a preconditioning manner, although the mechanism of TRX induction by temocapril remains to be elucidated.

Insulin ameliorates miR-1-induced injury in H9c2 cells under oxidative stress via Akt activation

Growing evidence indicates that aberrant upregulation of microRNA-1 (miR-1) occurs in ischemic myocardium. In addition, insulin elicits metabolism-independent cardioprotection against cardiovascular diseases. The aim of this study is to determine whether insulin ameliorates miR-1-induced injury in H9c2 cells under oxidative stress and to investigate the underlying mechanisms. By quantitative real-time RT-PCR (qRT-PCR), we show that miR-1 is upregulated in H9c2 cells after treatment with hydrogen peroxide (H2O2), and this effect is both dose- and time dependent. Furthermore, expression of miR-1 decreased significantly after insulin treatment (4.5xa0±xa00.1 vs. 3.0xa0±xa00.2, pxa0<xa00.05). To determine the potential role of miR-1 in cellular injury and gene regulation, adenovirus-mediated overexpression of miR-1 was used. Overexpression of miR-1 decreased cell viability by 28xa0±xa02xa0% (nxa0=xa06, pxa0<xa00.05) and damaged Akt activation with or without H2O2 treatment. To further investigate the effect of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway in miR-1-induced injury, H9c2 cells were pretreated with LY294002 (10xa0μM LY, a specific inhibitor of PI3K) with or without insulin (100xa0nM) and subjected to H2O2 treatment. LY pretreatment-inhibited Akt activation, lead to increased reactive oxygen species (ROS), and further decreased cell viability induced by miR-1 (nxa0=xa06, pxa0<xa00.05, nxa0=xa09–10xa0cells/group, pxa0<xa00.05 and nxa0=xa06, pxa0<xa00.05) under oxidative stress. This effect was abolished by insulin. In summary, our findings suggest that miR-1expression is sensitive to H2O2 stimulation. In addition, insulin decreases miR-1 expression and induces a marked protective effect on miR-1-induced injury under oxidative stress, which may be mediated by the Akt-mediated pathway. These results provide an important, novel clue as to the mechanism of the cardiovascular action of insulin.

Cardioprotective effects of carvedilol on acute autoimmune myocarditis.

We investigated whether carvedilol protects against experimental autoimmune myocarditis (EAM) attributing to antioxidant properties. Acute EAM was induced by porcine cardiac myosin in Lewis rats. We orally administered a vehicle, various dosages of carvedilol, metoprolol, or propranolol to rats with EAM for 3 weeks. Three β-blockers decreased heart rates to the same extent. Carvedilol, but not metoprolol or propranolol, markedly reduced the severity of myocarditis at the two different dosages. Only carvedilol decreased the myocardial protein carbonyl contents, and also decreased the myocardial thiobarbituric acid reactive substance products in rats with EAM. Accordingly, carvedilol protects against acute EAM in rats, and this superior cardioprotective effect of carvedilol to metoprolol and propranolol may be due to the antioxidant properties in addition to the hemodynamic modifications.

Beneficial effects of olmesartan, a novel angiotensin II receptor type 1 antagonist, upon acute autoimmune myocarditis.

Excess amount of cytokine produced by inflammatory stimuli contributes to the progression of myocardial damage in myocarditis. Some angiotensin II receptor type 1 antagonists are reported to inhibit proinflammatory cytokine production in vitro and in vivo. We tested the hypothesis that olmesartan, a novel angiotensin II receptor type 1 antagonist, ameliorated experimental autoimmune myocarditis (EAM) in rats attributing to the suppression of inflammatory cytokines in the heart. We orally administered olmesartan 1, 3, and 10 mg/kg/day to rats with EAM for 3 weeks. The results showed that olmesartan decreased blood pressure significantly compared with the untreated group, but markedly reduced the severity of myocarditis by comparing the heart weight/body weight ratio, pericardial effusion scores, macroscopic scores and microscopic scores. Myocardial interleukin (IL)-1β expression by western blotting and IL-1β-positive staining cells by immunohistochemistry were significantly lower in rats with EAM given olmesartan treatment compared with those of rats given vehicle. We conclude that Olmesartan ameliorates acute EAM in rats. The cardioprotection of olmesartan may be due to suppression of inflammatory cytokines dependent of the hemodynamic modifications.

17β-Estradiol Suppresses the Macrophage Foam Cell Formation Associated with SOCS3

Evidence from clinical trials and animal experiments has shown that estrogen has anti-atherosclerotic effects when administered to young women or experimental animals. The mechanisms involve the modulation of vascular inflammation, growth factor expression, and oxidative stress injured arteries. However, whether estrogen modulates the foam cell formation in plaque remains unknown. Here, we investigated the effects of 17β-estradiol (E2) on cholesterol efflux in vivo and in vitro. ApoE null mice underwent an ovariectomy at 5(th) week of age and then were treated with E2 or vehicle for the following 8 weeks. Compared with the vehicle-treated mice, the serum total cholesterol level, atherosclerotic plaque size, and lipid deposits were decreased and meanwhile ATP-binding cassette transporter A1 (ABCA1) expression in the plaque was increased in mice with E2 treatment. E2 also increased suppressor of cytokine signaling 3 (SOCS3) expression in the atherosclerotic plaques and in RAW264.7 cells. In vitro, E2 treatment reversed janus kinase/signal transducers and activators of transcription (JAK/STAT)-inhibited ABCA1 expression in RAW264.7 cells but had no effect on ABCA1 expression in SOCS3 knockdown cells. SOCS3 overexpression elevated ABCA1 expression through the inhibition of JAK2/STAT3 phosphorylation. Finally, we also found that E2 enhanced the cholesterol efflux to apoA I in RAW264.7 cells. In summary, E2 reduces atherosclerosis in ApoE null mice associated with upregulating ABCA1 expression and modulating the cholesterol efflux, which are dependent on SOCS3 upregulation. These results provide new insight into the athero-protective effects of estrogen.

Pioglitazone modulates the balance of effector and regulatory T cells in apolipoprotein E deficient mice.

BACKGROUND AND AIMSnPioglitazone (PIO) affects T cell-mediated immunity through actions of peroxisome proliferator activated receptor γ (PPARγ). Effector and regulatory T cells control the development of atherosclerosis, a chronic inflammatory disease affecting the arterial blood vessels. The aim of this study was to examine whether PIO ameliorates atherosclerosis by altering the balance of effector and regulatory T cells.nnnMETHODS AND RESULTSnTo explore the effect of PIO on early and advanced atherosclerosis, apolipoprotein E deficient (ApoE-/-) mice were fed western diet and received PIO (20 mg/kg/day) by gastric gavage at 6 or 14 weeks of age, respectively for 8 weeks. Data showed PIO markedly inhibited early fatty streak formation. Further, although the advanced fibrofatty plaque sizes were not significantly reduced, the numbers of smooth muscle cells within lesions were increased and higher collagen concentrations were produced. In general, macrophage expression in lesions was decreased. Additionally, the expression of Foxp3(+) cells was increased in lesions and spleens in mice at all PIO treatment stages, whereas the CD4(+)IFN-γ(+)/CD4(+)IL-4(+) cell ratios were reduced.nnnCONCLUSIONnPIO inhibited early atherosclerotic lesion formation and increased the stability of advanced atherosclerotic plaques in ApoE-/- mice, which was associated with altering the balance of effector and regulatory T cells.

L‐arginine ameliorates experimental autoimmune myocarditis by maintaining extracellular matrix and reducing cytotoxic activity of lymphocytes

It was previously shown that administration of the nitric oxide synthase inhibitor NG‐nitro‐l‐arginine methyl ester (l‐NAME) aggravated murine viral myocarditis by increasing myocardial virus titres. Experimental autoimmune myocarditis in mice and rats mimics human fulminant myocarditis. The effects of l‐arginine, a precursor of nitric oxide, upon heart failure in experimental autoimmune myocarditis were evaluated. Dietary l‐arginine (l‐arginine group) and l‐arginine plus NG‐nitro‐l‐arginine methyl ester (l‐arginineu2003+u2003l‐NAME group) were administered to C57BL/6 mice immunized with porcine cardiac myosin over 3u2003weeks. An untreated myocarditis group was prepared. Cardiac damage was less in the l‐arginine group compared with the other two groups, as was incidence of heart failure. In addition, extracellular matrix change was less prominent in the l‐arginine group. Plasma concentrations of nitric oxide were elevated in the l‐arginine group. Cytotoxic activities of lymphocytes were lower in l‐arginine group than in other two groups. l‐arginine treatment may be effective in preventing the development of heart failure in experimental myocarditis by maintaining extracellular matrix and reducing the cytotoxic activity of lymphocytes.