Elevated cyclic adenosine monophosphate ameliorates ischemia-reperfusion injury in rat cardiac allografts

Activation of endogenous anti-inflammatory mediator cyclic AMP attenuates acute pyelonephritis in mice induced by uropathogenic Escherichia coli

The pathogenesis of pyelonephritis caused by uropathogenic Escherichia coli (UPEC) is not well understood. Here, we show that besides UPEC virulence, the severity of the host innate immune response and invasion of renal epithelial cells are important pathogenic factors. Activation of endogenous anti-inflammatory mediator cAMP significantly attenuated acute pyelonephritis in mice induced by UPEC. Administration of forskolin (a potent elevator of intracellular cAMP) reduced kidney infection (ie, bacterial load, tissue destruction); this was associated with attenuated local inflammation, as evidenced by the reduction of renal production of proinflammatory mediators, renal infiltration of inflammatory cells, and renal myeloperoxidase activity. In primary cell culture systems, forskolin not only down-regulated UPEC-stimulated production of proinflammatory mediators by renal tubular epithelial cells and inflammatory cells (eg, monocyte/macrophages) but also reduced bacterial internalization by renal tubular epithelial cells. Our findings clearly indicate that activation of endogenous anti-inflammatory mediator cAMP is beneficial for controlling UPEC-mediated acute pyelonephritis in mice. The beneficial effect can be explained at least in part by limiting excessive inflammatory responses through acting on both renal tubular epithelial cells and inflammatory cells and by inhibiting bacteria invasion of renal tubular epithelial cells.

Abscisic acid ameliorates atherosclerosis by suppressing macrophage and CD4+ T cell recruitment into the aortic wall

Abscisic acid (ABA) is a natural phytohormone which improves insulin sensitivity and reduces adipose tissue inflammation when supplemented into diets of obese mice. The objective of this study was to investigate the mechanisms by which ABA prevents or ameliorates atherosclerosis. apolipoprotein E-deficient (ApoE(-/-)) mice were fed high-fat diets with or without ABA for 84 days. Systolic blood pressure was assessed on Days 0, 28, 56 and 72. Gene expression, immune cell infiltration and histological lesions were evaluated in the aortic root wall. Human aortic endothelial cells were used to examine the effect of ABA on 3',5'-cyclic adenosine monophosphate (cAMP) and nitric oxide (NO) production in vitro. We report that ABA-treated mice had significantly improved systolic blood pressure and decreased accumulation of F4/80(+)CD11b(+) macrophages and CD4(+) T cells in aortic root walls. At the molecular level, ABA significantly enhanced aortic endothelial nitric oxide synthase (eNOS) and tended to suppress aortic vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1) expression and plasma MCP-1 concentrations. ABA also caused a dose-dependent increase in intracellular concentrations of cAMP and NO and up-regulated eNOS mRNA expression in human aortic endothelial cells. This is the first report showing that ABA prevents or ameliorates atherosclerosis-induced hypertension, immune cell recruitment into the aortic root wall and up-regulates aortic eNOS expression in ApoE(-/-) mice.

Microarray-based Gene Expression Profiling of Retransplanted Rat Cardiac Allografts That Develop Cardiac Allograft Vasculopathy

We studied the expression of 9,906 genes in retransplanted rat cardiac allografts that developed cardiac allograft vasculopathy (CAV) with the use of DNA microarray and real-time reverse transcriptase-polymerase chain reaction. Although only a slight difference in the timing of the retransplantation induced the later development of CAV, 1,067 genes were differentially expressed in the allografts 1 day after retransplantation. Thus, the development of CAV was determined by a robust difference in gene expression soon after retransplantation, controlled by a slight difference in retransplantation timing. In contrast, only 26 genes showed significant upregulation in the later phase of CAV development, and the time-course of the induction of 16 genes was associated with CAV progression. Of these genes, 8 were induced in 2 different aortic allograft combinations, and the time-course of the induction was correlated with the development of transplant vasculopathy. Microarray-based gene expression profiling has the potential to elucidate the mechanism of experimental chronic cardiac allograft rejection.

Tissue factor mediates inflammation

The role of tissue factor (TF) in inflammation is mediated by blood coagulation. TF initiates the extrinsic blood coagulation that proceeds as an extracellular signaling cascade by a series of active serine proteases: FVIIa, FXa, and thrombin (FIIa) for fibrin clot production in the presence of phospholipids and Ca2+. TF upregulation resulting from its enhanced exposure to clotting factor FVII/FVIIa often manifests not only hypercoagulable but also inflammatory state. Coagulant mediators (FVIIa, FXa, and FIIa) are proinflammatory, which are largely transmitted by protease-activated receptors (PAR) to elicit inflammation including the expression of tissue necrosis factor, interleukins, adhesion molecules (MCP-1, ICAM-1, VCAM-1, selectins, etc.), and growth factors (VEGF, PDGF, bFGF, etc.). In addition, fibrin, and its fragments are also able to promote inflammation. In the event of TF hypercoagulability accompanied by the elevations in clotting signals including fibrin overproduction, the inflammatory consequence could be enormous. Antagonism to coagulation-dependent inflammation includes (1) TF downregulation, (2) anti-coagulation, and (3) PAR blockade. TF downregulation and anti-coagulation prevent and limit the proceeding of coagulation cascade in the generation of proinflammatory coagulant signals, while PAR antagonists block the transmission of such signals. These approaches are of significance in interrupting the coagulation-inflammation cycle in contribution to not only anti-inflammation but also anti-thrombosis for cardioprotection.

Superoxide Dismutase Mimetic M40401 Reduces Ischemia-Reperfusion Injury and Graft Coronary Artery Disease in Rodent Cardiac Allografts

BACKGROUND

The oxidative stress associated with ischemia-reperfusion (I/R) of cardiac allografts leads to production of injurious cytokines and expression of proinflammatory adhesion molecules. This is one of the most important alloantigen-independent factors associated with graft coronary artery disease (GCAD). M40401 is a newly developed cell permeable superoxide dismutase mimetic, which has been shown to scavenge superoxide anion with highly specific and enhanced catalytic activity. We hypothesized that M40401 would exert a protective effect in I/R injury of cardiac allografts and ameliorate the progression of GCAD.

METHODS

Recipient ACI rats were pretreated with M40401 or vehicle control. PVG donor hearts were heterotopically transplanted into the abdomen of ACI recipients. Cardiac allografts were analyzed for adhesion molecule mRNA expression and tumor necrosis factor-alpha expression after 4 hr of reperfusion. Neutrophil infiltration was detected by myeloperoxidase activity. Intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and endothelial leukocyte adhesion molecule-1 mRNA were detected by reverse-transcriptase polymerase chain reaction. Immunohistochemical analysis of adhesion molecule expression was also performed. Additional grafts were procured 90 days after transplantation and assessed for the development of GCAD by computer-assisted image analysis.

RESULTS

In the M40401-treated group, adhesion molecule expression was significantly less than in the vehicle control group. Treated grafts also had lower myeloperoxidase activity and tumor necrosis factor-alpha concentration compared with controls. Neointimal proliferation and intima to media ratios in M40401-treated allografts were significantly decreased compared with controls.

CONCLUSIONS

Selective removal of superoxide anion by M40401 results in inhibition of I/R injury. Furthermore, M40401 treatment decreases the development of oxidative stress-associated GCAD. This treatment strategy may have broad cardioprotective applications for all cardiac operations in addition to cardiac transplantation.