Role In Organ Injury Research Articles

Dexmedetomidine alleviates pulmonary fibrosis through the ADORA2B-Mediated MAPK signaling pathway

BackgroundIdiopathic pulmonary fibrosis (IPF) is a chronically progressive fibrotic pulmonary disease characterized by an uncertain etiology, a poor prognosis, and a paucity of efficacious treatment options. Dexmedetomidine (Dex), an anesthetic-sparing alpha-2 adrenoceptor (α2AR) agonist, plays a crucial role in organ injury and fibrosis. However, the underlying mechanisms of IPF remain unknown.MethodsIn our study, the role of Dex in murine pulmonary fibrosis models was determined by Dex injection intraperitoneally in vivo. Fibroblast activation and myofibroblast differentiation were assessed after Dex treatment in vitro. The activation of MAPK pathway and the expression of Adenosine A2B receptor (ADORA2B) were examined in lung myofibroblasts. Moreover, the role of ADORA2B in Dex suppressing myofibroblast differentiation and pulmonary fibrosis was determined using the ADORA2B agonist BAY60-6583.ResultsThe results revealed that Dex could inhibit Bleo-induced pulmonary fibrosis in mice. In vitro studies revealed that Dex suppressed TGF-β-mediated MAPK pathway activation and myofibroblast differentiation. Furthermore, Dex inhibits myofibroblast differentiation and pulmonary fibrosis via downregulating ADORA2B expression.ConclusionsOur findings suggest Dex as a potential therapeutic agent for pulmonary fibrosis. Dex may alleviate lung fibrosis and myofibroblast differentiation through the ADORA2B-mediated MAPK signaling pathway.

A non-canonical vitamin K cycle is a potent ferroptosis suppressor

Ferroptosis, a non-apoptotic form of cell death marked by iron-dependent lipid peroxidation1, has a key role in organ injury, degenerative disease and vulnerability of therapy-resistant cancers2. Although substantial progress has been made in understanding the molecular processes relevant to ferroptosis, additional cell-extrinsic and cell-intrinsic processes that determine cell sensitivity toward ferroptosis remain unknown. Here we show that the fully reduced forms of vitamin K—a group of naphthoquinones that includes menaquinone and phylloquinone3—confer a strong anti-ferroptotic function, in addition to the conventional function linked to blood clotting by acting as a cofactor for γ-glutamyl carboxylase. Ferroptosis suppressor protein 1 (FSP1), a NAD(P)H-ubiquinone reductase and the second mainstay of ferroptosis control after glutathione peroxidase-44,5, was found to efficiently reduce vitamin K to its hydroquinone, a potent radical-trapping antioxidant and inhibitor of (phospho)lipid peroxidation. The FSP1-mediated reduction of vitamin K was also responsible for the antidotal effect of vitamin K against warfarin poisoning. It follows that FSP1 is the enzyme mediating warfarin-resistant vitamin K reduction in the canonical vitamin K cycle6. The FSP1-dependent non-canonical vitamin K cycle can act to protect cells against detrimental lipid peroxidation and ferroptosis.

Methylation-dependent antioxidant-redox imbalance regulates hypertensive kidney injury in aging

The prevalence of hypertension increases with age, and oxidative stress is a major contributing factor to the pathogenesis of hypertension-induced kidney damage in aging. The nicotinamide adenine dinucleotide phosphate (NADPH) family is one of the major sources of reactive oxygen species (ROS) generation, and several NADPH oxidase isoforms are highly expressed in the kidney. Although epigenetic protein modification plays a role in organ injury, the methylation of the oxidant-antioxidant defense system and their role in hypertension-induced kidney damage in aging remains underexplored. The present study investigated the role of NADPH oxidase 4, superoxide dismutases (SODs), catalase, and NOS in Ang-II induced kidney damage in aging. Wild type (WT, C57BL/6J) mice aged 12–14 and 75–78 weeks were used and treated with or without Ang-II (1000 ng/kg/min) for 4 weeks with control mice receiving saline. Aged mice with or without Ang-II exhibited higher mean BP, lower renal blood flow, and decreased renal vascular density compared to young mice. While superoxide, 4-HNE, p22phox, Nox4, iNOS were increased in the aged kidney, the expression of eNOS, MnSOD, CuSOD, catalase, Sirt1, and -3 as well as the ratio of GSH/GSSG, and activities of SODs and catalase were decreased compared to young control mice. The changes further deteriorated with Ang-II treatment. In Ang-II treated aged mice, the expressions of DNMTs were increased and associated with increased methylation of SODs, Sirt1, and Nox4. We conclude that hypermethylation of antioxidant enzymes in the aged kidney during hypertension worsens redox imbalance leading to kidney damage.

Methane-rich saline protects against concanavalin A-induced autoimmune hepatitis in mice through anti-inflammatory and anti-oxidative pathways

Methane is a common gas which has been reported to play a protective role in organ injury and presents an anti-inflammatory property. However, its effects on Concanavalin A (Con A)-induced autoimmune hepatitis (AIH) remain unknown. Thus, the aim of this study was to investigate the effects of methane on Con A-induced autoimmune hepatitis in mice and its underlying mechanism. Autoimmune hepatitis was induced by Con A (15 mg/kg) in healthy C57BL/6 mice and methane-rich saline (MS) (20 ml/kg) was intraperitoneally injected 30 min after the challenge with Con A. We found that methane treatment significantly reduced the elevated serum aminotransferase levels and ameliorated liver pathological damage. Furthermore, methane treatment obviously suppressed the secretion of proinflammatory cytokines including tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-6 (IL-6) and interleukin-1β (IL-1β) and increased anti-inflammatory cytokine interleukin-10 (IL-10). Moreover, we found that the levels of malondialdehyde (MDA) and 8-hydroxy-2ʹ-deoxyguanosine (8-OHdG) were highly increased while the activities of superoxide dismutase (SOD) and catalase (CAT) were decreased in liver with the injection of Con A, which was reversed by methane. Also, the data demonstrated that the phosphorylated IκB, NF-κB and P38 MAPK in liver were significantly down-regulated by methane. These results suggested that methane protected liver against Con A-induced injury through anti-inflammatory and anti-oxidative pathways.

Pyruvate alleviates lipid peroxidation and multiple-organ dysfunction in rats with hemorrhagic shock

ObjectivePyruvate can reduce lipid peroxidation, which plays a critical role in organ injury, in various models. However, it is not fully understood if this inhibition occurs in resuscitation of hemorrhagic shock (HS). This study examines effects of pyruvate Ringer solution (PR) in this respect in rats. MethodsRats, subjected to 45% blood loss, were randomly allocated to the 3 groups (n = 18): HS with no fluid resuscitation (group NR), HS resuscitated with lactated Ringer solution (LR) (group LR), and HS resuscitated with PR (group PR). Mean arterial pressure, plasma levels of thiobarbituric acid reactive substances (TBARS), and superoxide dismutase were measured at various time points until 360 minutes after hemorrhage. Visceral organs were harvested at the end for evaluations of the TBARS, antioxidant enzyme, and tissue water content. Other 54 rats with identical procedures without sampling were documented for 24-hour survival rates (n = 18) after fluid resuscitation. ResultsPyruvate Ringer solution significantly increased mean arterial pressure and decreased blood TBARS levels after lethal HS. It also reduced TBARS concentrations and glutathione peroxidase activities but significantly enhanced glutathione reductase activities in most organs and greatly improved the ratios of reduced glutathione over oxidized glutathione in various organs in group PR, compared to group LR. Furthermore, PR significantly improved various organ function and water contents relative to LR. Group PR showed a more than 2-fold higher 24-hour survival rate of group LR. ConclusionsPyruvate Ringer solution alleviated organ edema and injury and prompted survival partially through inhibition of lipid peroxidation in various organs in severe HS rats.

Inhibition of the Kupffer Cell and Neutralization of IL-10 Increase the Expression of Chemokines in the Lung in a Rat Peritonitis Model

Elimination of Kupffer cells (KCs) exacerbated acute lung injury and mortality by inhibiting serum interleukin (IL)-10 levels in a rat peritonitis model. Since infiltrating inflammatory cells play a pivotal role in organ injury, the specific purpose of this study was to determine whether elimination of the KC and systemic IL-10 affect the expression of inflammatory mediators and the number of infiltrating inflammatory cells in the lung in the peritonitis model. Rats were given saline or gadolinium chloride (GdCl(3)), a KC toxicant, 24 h before cecal ligation and puncture (CLP). Tissue and serum samples were harvested after CLP, and the expression of inflammatory mediators was investigated. In another set of experiments, anti-rat IL-10 antibodies (anti-IL-10 Abs) were injected immediately after CLP to investigate the effects of immunoneutralization of endogenous IL-10. Serum levels of proinflammatory cytokines and chemokines were significantly greater in the GdCl(3) group than the control group after CLP. Furthermore, expression inflammatory mediators, as well as the number of infiltrating inflammatory cells in the lung were significantly greater in the GdCl(3) group than the control group. Alternatively, serum levels of inflammatory cytokines and chemokines, and the number of infiltrating inflammatory cells into the lung also increased significantly in rats treated with anti-IL-10 Abs compared with IgG after CLP. Thus, depletion of KCs and neutralization of IL-10 increased the expression of chemokines and the number of infiltrating inflammatory cells in the lung, leading to exacerbated acute lung injury in sepsis.

Coagulation Activation and Organ Dysfunction Following Cardiac Surgery

Cardiac surgery with cardiopulmonary bypass (CPB) is associated with major inflammatory triggers that cause marked activation of the microcirculation. This inflammatory response is associated with significant organ dysfunction. How this response causes organ dysfunction is not well understood; consequently, few interventions exist to prevent or treat it. In other acute inflammatory conditions, such as sepsis, increased coagulation activation in the microcirculation may be a cause of organ injury. We documented the association between coagulation activation and organ dysfunction to investigate whether coagulation activation also plays a role in organ injury following cardiac surgery with CPB. Prospective study of 30 patients undergoing cardiac surgery with CPB. Prothrombin fragment (PTF) 1 + 2 and plasminogen activator inhibitor (PAI) activity were measured, and levels correlated with postoperative measures of organ function including the left-ventricular stroke work index, the Pao(2)/fraction of inspired oxygen (Fio(2)) ratio, and creatinine levels. PTF levels increased eightfold (p < 0.05), and PAI activity increased threefold (p < 0.05) over the first 4 h after CPB. PTF levels were correlated with deteriorations in the left-ventricular stroke work index (p = 0.04), the Pao(2)/Fio(2) ratio (p = 0.02), and creatinine levels (p = 0.02). Levels of coagulation activation are associated with markers of postoperative organ dysfunction. Additional studies are warranted to investigate whether strategies that limit coagulation activation are associated with reductions in postoperative organ dysfunction.

Membrane structural changes support the involvement of mitochondria in the bile salt-induced apoptosis of rat hepatocytes.

The accumulation of toxic bile salts within the hepatocyte plays a key role in organ injury during liver disease. Deoxycholate (DC) and glycochenodeoxycholate (GCDC) induce apoptosis in vitro and in vivo, perhaps through direct perturbation of mitochondrial membrane structure and function. In contrast, ursodeoxycholate (UDC) and its taurine-conjugated form (TUDC) appear to be protective. We show here that hydrophobic bile salts induced apoptosis in cultured rat hepatocytes, without modulating the expression of pro-apoptotic Bax protein, and caused cytochrome c release in isolated mitochondria. Co-incubation with UDC and TUDC prevented cell death and efflux of mitochondrial factors. Using spin-labelling techniques and EPR spectroscopy analysis of isolated rat liver mitochondria, we found significant structural changes at the membrane-water surface in mitochondria exposed to hydrophobic bile salts, including modified lipid polarity and fluidity, altered protein order and increased oxidative injury. UDC, TUDC and cyclosporin A almost completely abrogated DC- and GCDC-induced membrane perturbations. We conclude that the toxicity of hydrophobic bile salts to hepatocytes is mediated by cytochrome c release, through a mechanism associated with marked direct effects on mitochondrial membrane lipid polarity and fluidity, protein order and redox status, without modulation of pro-apoptotic Bax expression. UDC and TUDC can directly suppress disruption of mitochondrial membrane structure, which may represent an important mechanism of hepatoprotection by these bile salts.

Altered Leukocyte Immunophenotypes in Septic Shock: Studies of HLA-DR, CD11b, CD14, and IL-2R Expression

To evaluate the role of cellular activation markers and functional surface molecules in sepsis, specific immunophenotypes on peripheral blood leukocytes were studied in 40 subjects consisting of the following: (1) patients with septic shock; (2) patients with sepsis; (3) critically ill nonseptic patients; and (4) normal control subjects. These assays included phagocyte adhesion molecule CD11b expression, monocyte receptors HLA-DR and CD14, and lymphocyte activation markers IL-2R and HLA-DR. Patients with septic shock and sepsis had significantly increased neutrophil CD11b expression compared with normal subjects. Neutrophil HLA-DR expression did not significantly differ between groups. Monocytes from septic shock patients had significantly less HLA-DR expression than normal subjects and there was a trend toward a lower proportion of gated monocytes that expressed CD14 in septic shock patients. Septic shock patients had no significant increases in IL-2R or HLA-DR expression on CD3 lymphocytes compared with control subjects, but they had significantly lower numbers of total, CD3, CD4, and CD8 lymphocytes and a higher prevalence of anergy. Septic shock patients manifested an increase in neutrophil CD11b expression that may play a role in organ injury. In contrast, a more specific decrease in monocyte expression of functional antigens is also observed in patients with septic shock that may have implications for immunologic defense mechanisms.

Pentoxifylline attenuates neutrophil activation in experimental endotoxemia in chimpanzees.

Costimulation of neutrophils and cytokines may play an important role in organ injury in sepsis. Pentoxifylline inhibits various neutrophil functions in vitro, and attenuates endotoxin-induced production of TNF in both in vitro and in vivo models. To assess the effect of pentoxifylline on neutrophil activation in endotoxemia, nine adult chimpanzees (Pan troglodytes) were i.v. injected with saline (n = 2), Escherichia coli endotoxin (4 ng/kg; n = 4), or E. coli endotoxin (4 ng/kg) in combination with pentoxifylline (500 mg/3 h, starting 30 min before the endotoxin injection; n = 3). Serial blood samples were obtained for measurements of leukocyte counts and the granulocytic proteinases elastase complexed with alpha 1-antitrypsin and lactoferrin, and cytokines during the next 5 h. No changes were observed in the saline-treated chimpanzees. Endotoxin induced a marked leukocytosis and neutrophilia, which were slightly reduced by pentoxifylline. In contrast, pentoxifylline almost completely prevented endotoxin-induced neutrophil degranulation: peak elastase-alpha 1-antitrypsin was 164 +/- 21 ng/ml (mean +/- SE) after endotoxin alone, vs 71 +/- 7 ng/ml after endotoxin with pentoxifylline (t = 3 h; p < 0.05); peak lactoferrin was 329 +/- 15 and 182 +/- 5 ng/ml, respectively (t = 5 h; p < 0.05). Pentoxifylline also inhibited the endotoxin-induced release of TNF (271 +/- 26 vs 55 +/- 23 pg/ml at t = 1.5 h; p < 0.05) and IL-6 (225 +/- 42 vs 73 +/- 25 pg/ml at t = 2 h; p < 0.05). IL-8 release was not significantly inhibited by pentoxifylline. In none of the animals activation of the C system could be detected. We conclude that pentoxifylline attenuates neutrophil activation in endotoxemia in chimpanzees, probably in part by inhibiting the release of TNF.