Preconditioning decreases Bax expression, PMN accumulation and apoptosis in reperfused rat heart. (25/1555)

OBJECTIVE: Recent studies suggest that ischemic preconditioning (IPC) inhibits myocardial apoptosis after ischemia and reperfusion. This study tested the hypothesis that IPC reduces ischemia/reperfusion-induced myocardial apoptosis by inhibiting neutrophil (PMN) accumulation and altering expression of Bcl-2 and Bax proteins. METHODS: Eighteen rats were subjected to 30 min of left coronary artery occlusion followed by 180 min of reperfusion with IPC (5 min ischemia and 10 min of reperfusion, n = 10) or without IPC (n = 8). Myocardial apoptosis was detected histologically using the terminal transferase UTP nick end labeling (TUNEL) assay and confirmed by DNA ladder on agarose gel electrophoresis. PMN accumulation was detected immunohistochemically with anti-rat CD18 antibody (WT3) and expression of Bcl-2 and Bax proteins was analyzed using Western blot assay. RESULTS: IPC significantly decreased TUNEL positive cells (% total nuclei) in the ischemic zone from 28.6 +/- 2.8 to 3.4 +/- 0.9 (P < 0.05), consistent with the absence of DNA ladders in the IPC group. IPC significantly attenuated PMN accumulation (cells/mm2 myocardium) in the ischemic zone from 243 +/- 19 to 118 +/- 19 (P < 0.05). By regression analysis, there was a significant correlation between TUNEL positive cells and accumulated CD18 positive PMNs in the ischemic zone (r = 0.8, P < 0.001), which was shifted downward by IPC. Densitometrically, IPC significantly attenuated the ischemia/reperfusion-upregulated expression of Bax protein in the ischemic zone from 204 +/- 57% in the control group to 76 +/- 7% (P < 0.05), while the expression of Bcl-2 was not different from the non-ischemic zone in either group. CONCLUSION: These data suggest that ischemic preconditioning may reduce myocardial apoptosis by inhibiting PMN accumulation and down-regulating expression of Bax.  (+info)

p38 MAP kinase activation by Clostridium difficile toxin A mediates monocyte necrosis, IL-8 production, and enteritis. (26/1555)

Clostridium difficile toxin A causes acute neutrophil infiltration and intestinal mucosal injury. In cultured cells, toxin A inactivates Rho proteins by monoglucosylation. In monocytes, toxin A induces IL-8 production and necrosis by unknown mechanisms. We investigated the role of mitogen-activated protein (MAP) kinases in these events. In THP-1 monocytic cells, toxin A activated the 3 main MAP kinase cascades within 1 to 2 minutes. Activation of p38 was sustained, whereas stimulation of extracellular signal-regulated kinases and c-Jun NH(2)-terminal kinase was transient. Rho glucosylation became evident after 15 minutes. IL-8 gene expression was reduced by 70% by the MEK inhibitor PD98059 and abrogated by the p38 inhibitor SB203580 or by overexpression of dominant-negative mutants of the p38-activating kinases MKK3 and MKK6. SB203580 also blocked monocyte necrosis and IL-1beta release caused by toxin A but not by other toxins. Finally, in mouse ileum, SB203580 prevented toxin A-induced neutrophil recruitment by 92% and villous destruction by 90%. Thus, in monocytes exposed to toxin A, MAP kinase activation appears to precede Rho glucosylation and is required for IL-8 transcription and cell necrosis. p38 MAP kinase also mediates intestinal inflammation and mucosal damage induced by toxin A.  (+info)

Human Kaposi's sarcoma cell-mediated tumorigenesis in human immunodeficiency type 1 tat-expressing transgenic mice. (27/1555)

BACKGROUND: The human immunodeficiency virus type 1 (HIV-1) transactivator (Tat) protein has been linked to the development and course of Kaposi's sarcoma (KS) associated with acquired immunodeficiency disease syndrome (AIDS-KS). Tat is an 86-101 amino-acid protein encoded by two exons. To evaluate the growth-promoting effects of Tat in AIDS-KS in vivo, we developed transgenic mice expressing the one-exon-encoded 72 amino-acid protein (Tat(72)) and the two-exon-encoded 86 amino-acid protein (Tat(86)). METHODS: Human KS SLK cells were injected subcutaneously into CD4(+) T-cell-depleted male mice, and the tumors that formed after 3-4 weeks were recovered and analyzed for the expression of Tat protein(s), different cytokine messenger RNAs (mRNAs), and matrix metalloproteinases (MMPs). All statistical tests were two-sided. RESULTS: The average tumor weight was maximum in Tat(86) mice ( approximately 600 mg) compared with Tat(72) ( approximately 200 mg) and nontransgenic ( approximately 100 mg) mice (P<.005). Histologic examination of tumors showed spindle-shaped SLK cells with prominent infiltrates of inflammatory cells. All of the tumors from Tat mice expressed abundant Tat mRNA, suggesting that the infiltrating mouse cells actively expressed Tat. A comparison of the growth-promoting cytokines in the tumors from Tat(86)-transgenic and nontransgenic mice showed that the expression of the following cytokines was substantially increased in the tumors of the Tat(86) mice: tumor necrosis factor-alpha, interleukin 6, interleukin 8, granulocyte-macrophage colony-stimulating factor, and basic fibroblast growth factor. Furthermore, these tumors showed abundant expression of a 105-kd MMP activity associated with infiltrates of host leukocytes in the lesions. CONCLUSION: Our in vivo data clearly suggest that extracellular Tat can contribute to the growth and tumorigenesis of human KS cells.  (+info)

G-CSF and IL-8 but not GM-CSF correlate with severity of pulmonary neutrophilia in acute respiratory distress syndrome. (28/1555)

Activated neutrophils play a major role in the pathogenesis of acute respiratory distress syndrome (ARDS), and persistence of pulmonary neutrophilia is related to poor survival. Interleukin (IL)-8 is implicated in recruiting neutrophils to the lungs but it has been postulated that granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF), which can promote the survival of neutrophils by delaying apoptosis, may prolong the inflammatory response. The aim of this study was to investigate the levels of GM-CSF and G-CSF in the lungs of patients with ARDS and determine their relationship relative to IL-8 with levels of neutrophils and clinical outcome. The lungs of 31 patients with ARDS were sampled by means of bronchoalveolar lavage (BAL) and assays of the three cytokines were conducted via enzyme-linked immunosorbent assay. GM-CSF, G-CSF and IL-8 were all increased in the patients compared to healthy controls but concentrations of GM-CSF were much lower than those of G-CSF and IL-8 (GM-CSF+info)

Airway neutrophils and interleukin-17. (29/1555)

It is well known that exacerbations of obstructive airways disease such as asthma and chronic obstructive pulmonary disease are associated with an increased number of neutrophils in the airways. However, the mechanisms behind this phenomenon are poorly understood. There is in vivo experimental evidence that the number of airway neutrophils is controlled by certain T-lymphocytes, but the mediators responsible for this lymphocyte-related neutrophilia have not yet been identified. In this review, novel evidence that the T-lymphocyte-related cytokine interleukin (IL)-17 can link the activation of certain T-lymphocytes to the recruitment and activation of airway neutrophils is described. The IL-17-induced neutrophil recruitment is mediated via induced CXC chemokine release through steroid-sensitive mechanisms and is modulated by release of endogenous tachykinins. These effects of IL-17 are potentiated by other pro-inflammatory cytokines such as (IL-1beta) and tumour necrosis factor-alpha. Clinical studies are needed to evaluate whether or not targeting these mechanisms can provide a useful pharmacotherapeutical approach against exaggerated mobilization of neutrophils in obstructive airways disease.  (+info)

Transient infiltration of neutrophils into the thymus in association with apoptosis induced by whole-body X-irradiation. (30/1555)

Generally, the process of apoptosis does not cause leakage of noxious cytosolic contents and is therefore non-inflammatory. However, as previously shown, macrophages ingesting apoptotic CTLL-2 cells produced pro-inflammatory cytokines, particularly interleukin-8 (IL-8) and macrophage inflammatory protein-2 (MIP-2), a murine IL-8 homolog. This predicted that rapid and massive apoptosis may induce neutrophil accumulation in vivo. In this study, we tested this prediction by inducing apoptosis by whole-body X-irradiation in mice. After exposure to 4 Gy X-ray irradiation, mice exhibited considerable apoptosis of thymic cells, which was associated with transient infiltration of neutrophils as well as MIP-2 mRNA expression. In contrast, in p53-deficient mice in which irradiation-induced apoptosis was suppressed, as has been reported, infiltration of neutrophils into the thymus was less than that found in p53+/+ mice. Taken together, these results suggest that massive and rapid apoptosis can result in infiltration of neutrophils.  (+info)

Delayed wound healing in the absence of intercellular adhesion molecule-1 or L-selectin expression. (31/1555)

Inflammatory cells play a crucial role in wound healing, but the role of adhesion molecules including L-selectin and intercellular adhesion molecule-1 (ICAM-1) is not known in this process. We examined skin wound repair of excisional wounds in mice lacking L-selectin, ICAM-1, or both. The loss of ICAM-1 inhibited wound healing, keratinocyte migration from the edges of the wound toward the center, and granulation tissue formation. By contrast, L-selectin deficiency alone did not affect any of these parameters. However, the loss of both L-selectin and ICAM-1 resulted in inhibition of keratinocyte migration and granulation tissue formation beyond those caused by loss of ICAM-1 alone. Treatment of platelet-derived growth factor to the wounds normalized delayed wound healing in ICAM-1(-/-) mice, but not in L-selectin/ICAM-1(-/-) mice. Therefore, although ICAM-1 contributes to wound repair to a greater extent than L-selectin, a role for L-selectin was revealed in the absence of ICAM-1. The impaired wound repair was associated with reduced infiltration of neutrophils and macrophages in ICAM-1(-/-) and L-selectin/ICAM-1(-/-) mice. These results demonstrate a distinct role of ICAM-1 and L-selectin in wound healing and that the delayed wound healing in the absence of these molecules is likely because of decreased leukocyte accumulation into the wound site.  (+info)

Type 4 phosphodiesterase inhibitors attenuate respiratory syncytial virus-induced airway hyper-responsiveness and lung eosinophilia. (32/1555)

Viral respiratory infections are considered one of the triggers of exacerbations of asthma. In a model of virus-induced airway hyper-responsiveness (AHR), mice infected with human respiratory syncytial virus (RSV) were shown to develop AHR accompanied by lung eosinophilia. Inhibitors of cyclic nucleotide phosphodiesterase (PDE) have been shown to affect airway responsiveness and pulmonary allergic inflammation. In this study, we assessed the effects of type 4 PDE (PDE4) inhibitors on AHR following RSV infection and compared them with a PDE3 inhibitor. In mice infected by intranasal inoculation of RSV, treatment with the PDE4 inhibitor rolipram or Ro-20-1724 reduced both AHR and the eosinophil infiltration of the airways. In contrast, the PDE3 inhibitor, milrinone, did not influence airway responsiveness or eosinophilic inflammation. These results demonstrate that PDE4 inhibitors can modulate RSV-induced AHR and lung eosinophilia and indicate that they have a potential role in treating exacerbations of asthma triggered by viral infection.  (+info)