Xiaoliang Gan

Propofol prevents lung injury after intestinal ischemia–reperfusion by inhibiting the interaction between mast cell activation and oxidative stress

AIMS Both mast cells and oxidative stress are involved in acute lung injury (ALI) induced by intestinal ischemia-reperfusion (IIR). The aim of this study was to investigate whether propofol could improve IIR-induced ALI through inhibiting their interaction. MAIN METHODS Repetitive, brief IIR or IIR+compound 48/80 was performed in adult Sprague-Dawley rats pretreated with saline, apocynin or propofol. And their lungs were excised for histology, ELISA and protein-expression measurements 2h after reperfusion. KEY FINDINGS Rats pretreated with saline developed critical ALI 2h after IIR. We found significant elevations in lung injury scores, lung wet/dry ratio and gp91phox, p47phox, intercellular cell adhesion molecule-1 protein expressions and higher level of malondialdehyde, interleukin-6 contents, and myeloperoxidase activities, as well as significant reductions in superoxide dismutase activities, accompanied with increases in mast cell degranulation evidenced by significant increases in mast cell counts, β-hexosaminidase concentrations, and tryptase expression. And the lung injury was aggravated in the presence of compound 48/80. However, pretreated with propofol and apocynin not only ameliorated the IIR-mediated pulmonary changes beyond the biochemical changes but also reversed the changes that were aggravated by compound 48/80. SIGNIFICANCE Propofol protects against IIR-mediated ALI, most likely by inhibiting the interaction between oxidative stress and mast cell degranulation.

Mast cells activation contribute to small intestinal ischemia reperfusion induced acute lung injury in rats

BACKGROUND Small intestinal ischemia-reperfusion (IIR) injury may lead to severe local and remote tissue injury, especially acute lung injury (ALI). Mast cell activation plays an important role in IIR injury. It is unknown whether IIR mediates lung injury via mast cell activation. METHODS Adult SD rats were randomized into sham operated group (S), sole IIR group (IIR) in which rats were subjected to 75 min of superior mesenteric artery occlusion followed by 4h reperfusion, or IIR being respectively treated with the mast cell stabilizer Cromolyn Sodium (IIR+CS group), with the tryptase antagonist Protamine (IIR+P group), with the histamine receptor antagonist Ketotifen (IIR+K group), or with the mast cell degranulator Compound 48/80 (IIR+CP group). The above agents were, respectively, administrated intravenously 5 min before reperfusion. At the end of experiment, lung tissue was obtained for histologic assessment and assays for protein expressions of tryptase and mast cell protease 7(MCP7). Pulmonary mast cell number and levels of histamine, TNF-α and IL-8 were quantified. RESULTS IIR resulted in lung injury evidenced as significant increases in lung histological scores (P<0.05 IIR vs. S), accompanied with concomitant increases of mast cell counts and elevations in TNF-α and IL-8 concentrations and reductions in histamine levels (all P<0.05 IIR vs. S). IIR also increased lung tissue tryptase and MCP7 protein expressions (all P<0.05, IIR vs. S). Cromolyn Sodium, Ketotifen and Protamine significantly reduced whilst Compound 48/80 aggravated IIR mediated ALI and the above biochemical changes (P<0.05). CONCLUSIONS Mast cells activation play a critical role in IIR mediated ALI.

Propofol Attenuates Small Intestinal Ischemia Reperfusion Injury through Inhibiting NADPH Oxidase Mediated Mast Cell Activation

Both oxidative stress and mast cell (MC) degranulation participate in the process of small intestinal ischemia reperfusion (IIR) injury, and oxidative stress induces MC degranulation. Propofol, an anesthetic with antioxidant property, can attenuate IIR injury. We postulated that propofol can protect against IIR injury by inhibiting oxidative stress subsequent from NADPH oxidase mediated MC activation. Cultured RBL-2H3 cells were pretreated with antioxidant N-acetylcysteine (NAC) or propofol and subjected to hydrogen peroxide (H2O2) stimulation without or with MC degranulator compound 48/80 (CP). H2O2 significantly increased cells degranulation, which was abolished by NAC or propofol. MC degranulation by CP further aggravated H2O2 induced cell degranulation of small intestinal epithelial cell, IEC-6 cells, stimulated by tryptase. Rats subjected to IIR showed significant increases in cellular injury and elevations of NADPH oxidase subunits p47phox and gp91phox protein expression, increases of the specific lipid peroxidation product 15-F2t-Isoprostane and interleukin-6, and reductions in superoxide dismutase activity with concomitant enhancements in tryptase and β-hexosaminidase. MC degranulation by CP further aggravated IIR injury. And all these changes were attenuated by NAC or propofol pretreatment, which also abrogated CP-mediated exacerbation of IIR injury. It is concluded that pretreatment of propofol confers protection against IIR injury by suppressing NADPH oxidase mediated MC activation.

Antioxidant N-acetylcysteine attenuates the reduction of Brg1 protein expression in the myocardium of type 1 diabetic rats.

Brahma-related gene 1 (Brg1) is a key gene in inducing the expression of important endogenous antioxidant enzymes, including heme oxygenase-1 (HO-1) which is central to cardioprotection, while cardiac HO-1 expression is reduced in diabetes. It is unknown whether or not cardiac Brg1 expression is reduced in diabetes. We hypothesize that cardiac Brg1 expression is reduced in diabetes which can be restored by antioxidant treatment with N-acetylcysteine (NAC). Control (C) and streptozotocin-induced diabetic (D) rats were treated with NAC in drinking water or placebo for 4 weeks. Plasma and cardiac free15-F2t-isoprostane in diabetic rats were increased, accompanied with increased plasma levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin 6 (IL-6), while cardiac Brg1, p-STAT3 and HO-1 protein expression levels were significantly decreased. Left ventricle weight/body weight ratio was higher, while the peak velocities of early (E) and late (A) flow ratio was lower in diabetic than in C rats. NAC normalized tissue and plasma levels of 15-F2t-isoprostane, significantly increased cardiac Brg1, HO-1 and p-STAT3 protein expression levels and reduced TNF-alpha and IL-6, resulting in improved cardiac function. In conclusion, myocardial Brg1 is reduced in diabetes and enhancement of cardiac Brg1 expression may represent a novel mechanism whereby NAC confers cardioprotection.

The Mechanism of Sevoflurane Preconditioning-Induced Protections against Small Intestinal Ischemia Reperfusion Injury Is Independent of Mast Cell in Rats

The study aimed to investigate whether sevoflurane preconditioning can protect against small intestinal ischemia reperfusion (IIR) injury and to explore whether mast cell (MC) is involved in the protections provided by sevoflurane preconditioning. Sprague-Dawley rats exposed to sevoflurane or treated with MC stabilizer cromolyn sodium (CS) were subjected to 75-minute superior mesenteric artery occlusion followed by 2-hour reperfusion in the presence or absence of MC degranulator compound 48/80 (CP). Small intestinal ischemia reperfusion resulted in severe intestinal injury as demonstrated by significant elevations in intestinal injury scores and p47phox and gp91phox, ICAM-1 protein expressions and malondialdehyde and IL-6 contents, and MPO activities as well as significant reductions in SOD activities, accompanied with concomitant increases in mast cell degranulation evidenced by significant increases in MC counts, tryptase expression, and β-hexosaminidase concentrations, and those alterations were further upregulated in the presence of CP. Sevoflurane preconditioning dramatically attenuated the previous IIR-induced alterations except MC counts, tryptase, and β-hexosaminidase which were significantly reduced by CS treatment. Furthermore, CP exacerbated IIR injury was abrogated by CS but not by sevoflurane preconditioning. The data collectively indicate that sevoflurane preconditioning confers protections against IIR injury, and MC is not involved in the protective process.

Histamine at low concentrations aggravates rat liver BRL-3A cell injury induced by hypoxia/reoxygenation through histamine H2 receptor in vitro.

AIM Histamine released from mast cell degranulation participates in the pathogenesis of ischemia/reperfusion injury. The purpose of our study was to define the role of histamine in hypoxia/reoxygenation mediated liver cell injury and to elucidate the underlying mechanism in vitro. METHODS Histamine alone or in combination with H1 receptor antagonist (pyrilamine), H2 receptor antagonist (cimetidine) or H3/4 receptor antagonist (thioperamide) at different concentrations before hypoxia was added to rat liver BRL-3A cell which was subjected to 24h hypoxia followed by 4h reoxygenation. Cell proliferation, apoptosis and the changes of ultrastructure were assessed, and MDA contents, SOD activities and ALT levels were quantified as well. RESULTS Histamine (from 10(-3) to 10(-9) M) did not affect the growth of BRL-3A cells without hypoxia treatment. However, histamine 10(-8)M significantly lowered the growth of BRL-3A cells challenged by hypoxia/reoxygenation, accompanied with concomitant elevations in MDA contents and decreases in SOD activities, all these changes were blocked by cimetidine, not by pyrilamine or thioperamide. However, histamine (above 10(-6) M) did not show exacerbating effects in BRL-3A cell subjected to hypoxia/reoxygenation. CONCLUSION Histamine at low concentrations (10(-7)-10(-9) M) aggravates hypoxia/reoxygenation mediated BRL-3A damage through histamine H2 receptor.

Inhibiting tryptase after ischemia limits small intestinal ischemia-reperfusion injury through protease-activated receptor 2 in rats.

BACKGROUND Mast cell activation plays a key role in the process of small intestinal ischemia-reperfusion (IIR) injury; however, the precise role of tryptase released from mast cell on IIR injury remains poorly understood. The aim of this study was to determine the protective role against IIR injury by using tryptase inhibitor protamine after ischemia and to explore the underlying mechanism. METHODS Adult Sprague-Dawley rats were randomized into sham-operated group (S), sole IIR group (IIR) in which rats were subjected to 75-minute superior mesenteric artery occlusion followed by 4-hour reperfusion, or IIR being respectively treated with mast cell stabilizer cromolyn sodium (CS group), with the mast cell degranulator compound 48/80 (CP group), or with protamine (P group). The previously mentioned agents were, respectively, administered intravenously 5 minutes before reperfusion. The intestine tissue was obtained for histologic assessment and assays for protein expressions of tryptase and mast cell protease 7 and protease-activated receptor 2 (PAR-2). The intestine mast cell number and levels of tumor necrosis factor &kgr; and interleukin 8 were quantified. RESULTS IIR resulted in intestinal injury evidenced as significant increases in Chiu’s scores, accompanied with concomitant increases of mast cell counts and intestinal tryptase and mast cell protease 7 protein expressions. IIR also increased intestinal PAR-2 expressions, tumor necrosis factor &kgr;, and interleukin 8 levels. Cromolyn sodium and protamine significantly reduced the responses to IIR injury while compound 48/80 further aggravated the previously mentioned biochemical changes. CONCLUSION Tryptase releasing from mast cell activation participates in IIR injury through PAR-2, and inhibiting tryptase after ischemia provides promising benefits in limiting IIR injury.

Pivotal role of mast cell carboxypeptidase A in mediating protection against small intestinal ischemia-reperfusion injury in rats after ischemic preconditioning

AIM OF THE STUDY Mast cell (MC) degranulation contributes to the protection mediated by ischemic preconditioning (IPC); however, the precise mechanisms underlying this protection remain largely unknown. Mast cell carboxypeptidase A (MC-CPA) is released solely from MCs and plays a critical role in degrading toxins and endothelin 1 (ET-1). The present study sought to explore whether MC-CPA is involved in the process of IPC in a rodent model of small intestinal ischemia reperfusion (IIR) injury. MATERIALS AND METHODS IIR injuries were induced in Sprague-Dawley rats by clamping the superior mesenteric artery for 60 min followed by reperfusion for 2 h. One cycle of 10 min intestinal ischemia and 10 min of reperfusion was used in the IPC group, and the MC stabilizer cromolyn sodium and MC potato carboxypeptidase inhibitor were administered before the start of IPC. At the end of experiment, intestine tissue was obtained for assays of the MC-CPA3, tumor necrosis factor-α, interleukin-6, and ET-1 contents and myeloperoxidase activities. Intestinal histologic injury scores and MC degranulation were assessed. Apoptosis indices and cleaved caspase- 3 protein expressions were quantified. RESULTS IIR resulted in severe injury, as evidenced by significant increases in injury scores and MC-CPA3, tumor necrosis factor-α, interleukin-6, and ET-1 contents that were accompanied with concomitant elevations in cleaved caspase 3 expression, apoptosis indices, and myeloperoxidase activities. IPC induced a significant increase in MC-CPA3, induced MC degranulation, and attenuated IIR injury by downregulating IIR-induced biochemical changes, whereas cromolyn sodium and potato carboxypeptidase inhibitor abolished the IPC-mediated changes. CONCLUSIONS These data suggest that IPC protected against IIR injury via the MC degranulation-mediated release of MC-CPA.

Time-course analysis of counts and degranulation of mast cells during early intestinal ischemia-reperfusion injury in mice

Findings of previous studies have revealed that intestinal mucosal mast cells (IMMCs) are involved in small intestinal ischemia‑reperfusion injury (IIRI). However, time-course changes of mast cell counts and mast cell function in this process remain unclear. The present study aimed to observe the number of IMMCs and to investigate the correlation between their activation and small intestine injury at various time points during the period of small intestinal ischemia reperfusion (IIR). Healthy male Kunming mice were randomly divided into five groups, and were subjected to occlusion of the superior mesenteric artery (SMA) for 30 min and followed by reperfusion for 1, 3, 6 and 12 h. By contrast, the SMA was isolated but not clamped in the baseline group. Chius scores were assessed by light microscopy, tryptase protein and MCP7 protein expression in the intestine were quantified, and mast cell counts and levels of histamine and TNF-α in the intestine were measured. The results showed that IIR induced severe intestine injury within 12 h as demonstrated by Chius scores that was greatly increased as compared to the baseline group, accompanied by increased mast cell counts, histamine and TNF-α levels. However, the Chius scores were reduced in the IIR 12 h group compared with the IIR 1 h, IIR 3 h and IIR 6 h groups, with concomitant decreased mast cell counts, histamine and TNF-α levels. The tryptase and MCP7 protein expression was markedly increased in the IIR 1 h and IIR 3 h groups as compared with the baseline group, whereas this expression was gradually decreased at 6 and 12 h after reperfusion. The results of the present study suggest that IIR results in severe mucosal destruction within 6 h after reperfusion, associated with mast cell activation and substantial increases in the mast cell counts.

Lipopolysaccharide effects on the proliferation of NRK52E cells via alternations in gap-junction function.

BACKGROUND Gap junctions regulate proper kidney function by facilitating intercellular communication, vascular conduction, and tubular purinergic signaling. However, no clear relationship has been described between gap-junction function and acute kidney injury induced by the endotoxin lipopolysaccharide (LPS). METHODS Normal rat kidney epithelial cells (NRK52E cells) were seeded at high and low densities to promote or impede gap-junction formation, respectively, and establish distinctive levels of intercellular communication in culture. Cells were then challenged with LPS at various concentrations (10–1,000 ng/mL). LPS-induced formation and function of gap junctions were assessed by measuring changes in cell proliferation and colony-forming rates, fluorescent dye transmission to adjacent cells, expression levels of connexin43, and repositioning of confluent cells in response to the gap junction inhibitor oleamide or agonist retinoic acid. RESULTS The cell proliferation rate and colony-forming rate of high- and low-density NRK52E cells were decreased upon LPS challenge, in a dose-dependent manner. The colony-forming rate of confluent high-density cells was significantly lower than that of low-density cells. Oleamide treatment raised the LPS-induced colony-forming rate of high-density cells, whereas retinoic acid decreased the rate. Neither oleamide nor retinoic acid significantly affected the LPS-induced colony-forming rate of low-density cells. Fluorescence transmission of high-density cells was reduced by LPS challenge, in a dose-dependent manner, but inclusion of retinoic acid increased the LPS-induced transmission of fluorescence. LPS challenge of either high- or low-density NRK52E cells resulted in down-regulated connexin43 expression. CONCLUSION Gap-junction function plays an important role in concentration-dependent cytotoxic effect of LPS on normal rat kidney cells in vitro.