INDUCIBLE NITRIC OXIDE SYNTHASE INHIBITOR REVERSES EXACERBATING EFFECTS OF HYPERTONIC SALINE ON LUNG INJURY IN BURN

Parecoxib reduces systemic inflammation and acute lung injury in burned animals with delayed fluid resuscitation

Burn injuries result in the release of proinflammatory mediators causing both local and systemic inflammation. Multiple organ dysfunctions secondary to systemic inflammation after severe burn contribute to adverse outcome, with the lungs being the first organ to fail. In this study, we evaluate the anti-inflammatory effects of Parecoxib, a parenteral COX-2 inhibitor, in a delayed fluid resuscitation burned rat model. Anaesthetized Sprague Dawley rats were inflicted with 45% total body surface area full-thickness scald burns and subsequently subjected to delayed resuscitation with Hartmann's solution. Parecoxib (0.1, 1.0, and 10 mg/kg) was delivered intramuscularly 20 min after injury followed by 12 h interval and the rats were sacrificed at 6 h, 24 h, and 48 h. Burn rats developed elevated blood cytokines, transaminase, creatinine, and increased lung MPO levels. Animals treated with 1 mg/kg Parecoxib showed significantly reduced plasma level of CINC-1, IL-6, PGEM, and lung MPO. Treatment of 1 mg/kg Parecoxib is shown to mitigate systemic and lung inflammation without significantly affecting other organs. At present, no specific therapeutic agent is available to attenuate the systemic inflammatory response secondary to burn injury. The results suggest that Parecoxib may have the potential to be used both as an analgesic and ameliorate the effects of lung injury following burn.

Similar effects of hypertonic saline and mannitol on the inflammation of the blood-brain barrier microcirculation after brain injury in a mouse model

BACKGROUND

There has been substantial debate regarding the efficacy of hypertonic saline (HTS) versus mannitol (MTL) in treating moderate and severe traumatic brain injury (TBI). HTS blunts polymorphonuclear neutrophil (PMN) and endothelial cell (EC) activation and reduces tissue edema after resuscitated shock in systemic microvascular beds. MTL also modulates PMN activation markers. It remains unknown if either of these osmotherapies exert similar anti-inflammatory effects along the blood-brain barrier (BBB). We hypothesized that HTS, as compared with MTL, would more greatly reduce PMN-EC interactions, thereby reducing BBB permeability and tissue edema after simulated TBI.

METHODS

CD1 male mice (25-30 g) underwent craniotomy and window placement for observation of in vivo PMN-EC interactions in pial venules using intravital video microscopy. TBI was simulated through local suffusion of the brain surface with interleukin 1β (100 ng/0.1 mL). Animals were randomized to receive a single, equiosmolar, intravenous dose of 20% MTL or 5% HTS after injury. Live microcirculatory footage was obtained every 15 minutes for 2 hours, after which fluorescent-labeled albumin was administered to assess microvascular permeability. PMN rolling and adhesion and macromolecular leakage were analyzed offline by a blinded observer and postmortem brain and lung edema assessed by wet-to-dry ratios. Student's t test and Mann-Whitney U test determined significance (p ≤ 0.05).

RESULTS

Neither osmotherapy resulted in significant differences in PMN rolling or adhesion; however, both trended higher in HTS. Similarly, vessel permeability did not differ between groups but also trended higher with HTS. In contrast, brain and lung edema was greater in MTL than HTS as compared with controls (p = 0.05).

CONCLUSION

MTL and HTS have indistinguishable effects on PMN-EC interactions in the brain after simulated TBI. Additional studies are needed to determine if either osmotherapy has more subtle effects on BBB PMN-EC interactions after injury exerting a potential clinical advantage.

Hypertonic saline resuscitation of hemorrhagic shock does not decrease in vivo neutrophil interactions with endothelium in the blood-brain microcirculation

BACKGROUND

Resuscitation of hemorrhagic shock with isotonic crystalloids has been shown to activate polymorphonuclear neutrophils (PMNs). Although hypertonic saline (HTS) can reduce PMN activation and interactions with endothelial cells (EC) in systemic microvascular beds, no data exist demonstrating that the same occurs in the unique blood-brain barrier microcirculation. We hypothesized that resuscitation of hemorrhagic shock with HTS would blunt brain in vivo PMN-EC interactions.

METHODS

Wistar rats (250-350 g) underwent craniotomy and placement of a window for live intravital viewing of pial vessels. Twenty animals were bled to a mean arterial pressure of 30 mm Hg to 35 mm Hg for 1 hour and resuscitated with shed blood and either 5% HTS (6 mL/kg) or Ringer's lactate (RL) (2× shed blood volume). Circulating rhodamine-6G-labeled PMN in pial venules were captured by videomicroscopy at baseline (preshock), end of the shock period, after resuscitation, and every 15 minutes to 30 minutes for 2 hours. Hemodynamics and arterial gases were monitored. Off-line footage analysis allowed comparisons of PMN-EC interactions between groups.

RESULTS

Animals in both groups developed significant metabolic acidosis (p < 0.01) after hemorrhage, but postresuscitation blood pressures were similar at all time points. Crystalloid resuscitation volumes were 10× greater in RL than HTS animals (p < 0.001). For all time points, we did not observe the expected reduction in PMN rolling and adhesion in HTS animals, instead noted trends of consistently lower interactions in RL counterparts.

CONCLUSIONS

In contradistinction to studies evaluating the systemic microcirculation, HTS may activate PMN-EC crosstalk in the blood-brain microcirculation. Further studies are needed to analyze whether this effect is due to the unique nature of the blood-brain interface.

Estrogen augments the protection of hypertonic saline treatment from mesenteric ischemia-reperfusion injury

Either estrogen or hypertonic saline (HTS) administration can decrease lung inflammation after ischemia-reperfusion. The present study investigated whether combined treatment with estrogen and HTS could provide further protection from mesenteric ischemia-reperfusion (MSIR) injury. Male C3H/HeOuJ mice were randomly segregated into the following groups: sham-operated (sham), vehicle treatment followed by MSIR (vehicle treated), estrogen treatment followed by MSIR (estrogen treated), HTS treatment and MSIR (HTS treated), and combined treatment of estrogen plus HTS and MSIR (combined treated). In MSIR, mice were subjected to mesenteric ischemia for 60 min followed by reperfusion for 30 min. The histology of the lung and the gut was obtained. Lung injury was evaluated by lung edema and myeloperoxidase (MPO) activity; lung protein expression of macrophage migration inhibitory factor (MIF), toll-like receptor-4 (TLR4), phosphorylated inhibitory κBα (p-IκBα), and inducible nitric oxide synthetase (iNOS) were assayed. Survival analysis was monitored after MSIR for 120 min. Compared with those in the sham-treated group, the lung water ratio, MPO activity, and expressions of MIF, TLR4, p-IκBα, and iNOS were significantly increased in the vehicle-treated group. Diminished MIF, TLR4, p-IκBα, and iNOS expressions were found in the estrogen-treated group, whereas suppression of p-IκBα and iNOS was found in the HTS-treated group. Treatment with estrogen or HTS decreased the lung water and MPO activity. The combined treatment of estrogen and HTS further significantly diminished p-IκBα and iNOS expression, lung edema, and MPO activity and improved the inflammation of the lung and the morphology of the gut in histology compared with the results of a single treatment of estrogen or HTS. Survival analysis showed significantly increased survival in the combination-treated group compared with survival in the HTS-treated group. In conclusion, compared with single-agent use, treatment combining estrogen and HTS further decreases lung p-IκBα and iNOS expressions, as well as the degree of lung injury. These effects may result in better rates of survival from MSIR injury.

Magnolol attenuates the lung injury in hypertonic saline treatment from mesenteric ischemia reperfusion through diminishing iNOS

BACKGROUND

Hypertonic saline (HTS) administration can decrease the inflammation following ischemia reperfusion. Magnolol is a potent antioxidant. The present study investigated whether combined treatment of magnolol and HTS could provide further protection in mesenteric ischemia reperfusion injury.

METHODS

Male C3H/HeOuJ mice were randomly segregated into the following groups: sham-operated (sham), vehicle treatment and mesenteric ischemia reperfusion (MSIR) (vehicle-treated), magnolol treatment and MSIR (magnolol-treated), HTS treatment and MSIR (HTS-treated), as well as co-administration of magnolol plus HTS and MSIR (combined-treated). In MSIR, mice were subjected to mesenteric ischemia for 60 min followed by reperfusion for 30 min. Lung injury was evaluated by lung edema (water ratio) and myeloperoxide (MPO) activity; RNA expression of inducible nitric oxide synthetase (iNOS), TNF-α, and IL-6 were assayed by real time RT-PCR. The formation of peroxynitrite in plasma was assayed by the peroxynitrite-dependent oxidation of dihydrorhodamine 123 (DHR 123) to rhodamine.

RESULTS

Compared with those in the sham-treated group, lung edema and MPO activity, expressions of iNOS, TNF-α and IL-6, and plasma peroxynitrite were significantly increased in the vehicle-treated group. Significant attenuations of these parameters were found in the magnolol-treated or HTS-treated animals. Combined treatment of magnolol and HTS further suppressed the lung edema, iNOS, and TNF-α expressions, and plasma peroxynitrite, compared with the results of a single treatment of magnolol or HTS.

CONCLUSIONS

Compared with single-agent use, co-administration of magnolol and HTS further decreases iNOS expression and plasma peroxynitrite as well as the degree of lung injury from MISR. These results may provide another treatment measure for post-injury immunomodulation.

Mechanistic aspects of inducible nitric oxide synthase-induced lung injury in burn trauma

INTRODUCTION

Although the beneficial effects of inducible nitric oxide synthase (iNOS) inhibition in acute lung injury secondary to cutaneous burn and smoke inhalation were previously demonstrated, the mechanistic aspects are not completely understood. The objective of the present study is to describe the mechanism(s) underlying these favourable effects. We hypothesised that iNOS inhibition prevents formation of excessive reactive nitrogen species and attenuates the activation of poly(ADP) (poly(adenosine diphosphate)) ribose polymerase, thus mitigating the severity of acute lung injury in sheep subjected to combined burn and smoke inhalation.

METHODS

Adult ewes were chronically instrumented for a 24-h study and allocated to groups: sham: not injured, not treated, n = 6; control: injured, not treated, n = 6; and BBS-2: injured treated with iNOS dimerisation inhibitor BBS-2, n = 6. Control and BBS-2 groups received 40% total body surface area 3rd-degree cutaneous burn and cotton smoke insufflation into the lungs under isoflurane anaesthesia.

RESULTS

Treatment with iNOS inhibitor BBS-2 significantly improved pulmonary gas exchange (partial pressure of oxygen in the blood/fraction of inspired oxygen (PaO₂/FiO₂) 409 ± 43 mmHg vs. 233 ± 50 mmHg in controls, p < 0.05) and reduced airway pressures (peak pressure 20 ± 1 cm H₂O vs. 28 ± 2 cm H₂O in controls, p < 0.05) and lung water content (lung wet-to-dry ratio 4.1 ± 0.3 vs. 5.2 ± 0.2 in controls, p < 0.05) 24h after the burn and smoke injury. BBS-2 significantly reduced the increases in lung lymph nitrite/nitrate (10 ± 3 μM vs. 26 ± 6 μM in controls, p < 0.05) and 3-nitrotyrosine (109 ± 11 (densitometry value) vs. 151 ± 18 in controls, p < 0.05). Burn/smoke-induced increases in lung tissue nitrite/nitrate, poly(ADP)ribose polymerase, nuclear factor-κB (NF-κB) activity, myeloperoxidase activity and malondialdehyde formation and interleukin (IL)-8 expression were also attenuated with BBS-2.

CONCLUSIONS

The results provide strong evidence that BBS-2 ameliorated acute lung injury by inhibiting the inducible nitric oxide synthase/reactive nitrogen species/poly(ADP-ribose) polymerase (iNOS/RNS/PARP) pathway.

Activated protein C modulates chemokine response and tissue injury in experimental sepsis

The protein C (PC) pathway plays an important role in vascular function, and acquired deficiency during sepsis is associated with increased mortality. We have explored the role of PC suppression in modulating early inflammatory events in a model of polymicrobial sepsis. We show that increased levels of organ damage and dysfunction are associated with decreased levels of endogenous PC. Notably, animals with low PC had correspondingly high levels of pulmonary iNOS expression, which correlated with chemokines KC/Gro and MIP2, previously shown to predict outcome in this model. Treatment with activated protein C (aPC) not only reduced the pathology score, leukocyte infiltration and markers of organ dysfunction, but also suppressed the induction of iNOS, and the chemokine response (including KC/Gro, MIP2, IP-10, RANTES, GCP-2 and lymphotactin), and increased apoA1. aPC treatment also suppressed the induction of VEGF, a marker recently suggested to play a pathophysiological role in sepsis. These data demonstrate a clear link between low protein C and degree of organ damage and dysfunction in sepsis, as well as the early reversal with aPC treatment. Moreover, our data show a direct role of aPC in broadly modulating monocyte and T-cell chemokines following systemic inflammatory response.

Role of protein C in renal dysfunction after polymicrobial sepsis

Protein C (PC) plays an important role in vascular function, and acquired deficiency during sepsis is associated with increased mortality in both animal models and in clinical studies. This study explored the consequences of PC suppression on the kidney in a cecal ligation and puncture model of polymicrobial sepsis. This study shows that a rapid drop in PC after sepsis is strongly associated with an increase in blood urea nitrogen, renal pathology, and expression of known markers of renal injury, including neutrophil gelatinase-associated lipocalin, CXCL1, and CXCL2. The endothelial PC receptor, which is required for the anti-inflammatory and antiapoptotic activity of activated PC (APC), was significantly increased after cecal ligation and puncture as well as in the microvasculature of human kidneys after injury. Treatment of septic animals with APC reduced blood urea nitrogen, renal pathology, and chemokine expression and dramatically reduced the induction of inducible nitric oxide synthase and caspase-3 activation in the kidney. The data demonstrate a clear link between acquired PC deficiency and renal dysfunction in sepsis and suggest a compensatory upregulation of the signaling receptor. Moreover, these data suggest that APC treatment may be effective in reducing inflammatory and apoptotic insult during sepsis-induced acute renal failure.

Rosiglitazone, a peroxisome proliferator-activated receptor-gamma agonist, reduces acute lung injury in endotoxemic rats

OBJECTIVE

Rosiglitazone, a potent agonist of peroxisome proliferator-activated receptor (PPAR)-gamma, exerts anti-inflammatory effects in vitro and in vivo. This study was designated to determine the effects of rosiglitazone on endotoxin-induced acute lung injury in rats.

DESIGN

Prospective, experimental study.

SETTING

University research laboratory.

SUBJECTS

Thirty-six male Wistar rats.

INTERVENTIONS

All the animals were randomly assigned to one of six groups (n = 6 per group) and were given either lipopolysaccharide (6 mg/kg intravenously) or saline, pretreated with rosiglitazone (0.3 mg/kg intravenously) or vehicle (10% dimethyl sulphoxide) 30 mins before lipopolysaccharide. The selective PPAR-gamma antagonist GW9662 (0.3 mg/kg intravenously) or its vehicle (10% dimethyl sulphoxide) was given 20 mins before rosiglitazone.

MEASUREMENTS AND MAIN RESULTS

Endotoxemia for 4 hrs induced evident lung histologic injury and edema, both of which were significantly attenuated by rosiglitazone pretreatment. The protective effects of rosiglitazone were correlated with the reduction by 71% of the increase of myeloperoxidase activity and the reduction by 84% of the increase of malondialdehyde in the lung tissue. The pulmonary hyperproduction of nitric oxide was reduced by 82% of the increase related to lipopolysaccharide challenge. Pretreatment with rosiglitazone also markedly suppressed lipopolysaccharide-induced expression of inducible nitric oxide synthase messenger RNA and protein in the lung, as demonstrated by reverse transcription-polymerase chain reaction or Western blot analysis. Immunohistochemical analysis revealed that rosiglitazone inhibited the formation of nitrotyrosine, a marker for peroxynitrite reactivity, in the lung tissue. In addition, the specific PPAR-gamma antagonist GW9662 antagonized the effects of rosiglitazone.

CONCLUSIONS

This study provides evidence, for the first time, that the PPAR-gamma agonist rosiglitazone significantly reduces endotoxin-induced acute lung injury in rats.

Flurbiprofen and HCT1026 protect mice against acute pancreatitis-associated lung injury

Impaired lung function in severe acute pancreatitis is the primary cause of morbidity and mortality in this condition. Flurbiprofen is a powerful nonsteroidal anti-inflammatory drug (NSAID). However, administration of this drug is associated with severe gastrointestinal side effects. The NO-releasing derivative of flubiprofen (nitroflurbiprofen, HCT1026) has recently been developed by the addition of a nitroxybutyl moiety to the flurbiprofen structure. This modification does not interfere with the anti-inflammatory activity of the drug but markedly reduces its ability to induce gastric injury. The effects of treatment with flurbiprofen and HCT1026 on the severity of pancreatitis and the associated lung injury were investigated in a mouse model. Acute pancreatitis was induced in mice by hourly intraperitoneal injections of cerulein. Flurbiprofen and HCT1026 were administered either 30 min before or 1 h after starting cerulein injections, and the severity of acute pancreatitis and associated lung injury were assessed. The severity of acute pancreatitis was determined by hyperamylasemia, neutrophil sequestration in the pancreas (pancreatic MPO activity), and pancreatic acinar cell injury/necrosis on histological examination of pancreas sections. The severity of acute pancreatitis-associated lung injury was assessed by neutrophil sequestration in the lungs (lung MPO activity) and by histological examination of lung sections. HCT1026 and flurbiprofen, given prophylactically as well as therapeutically, significantly reduced lung inflammation without having any significant effect on pancreatic injury. These results suggest the usefulness of flurbiprofen as well as HCT1026 as potential treatments for pancreatitis-associated lung injury.