Burn Injury Group Research Articles

Expression of microRNA-126 in myocardial tissue of rats in the early stage of severe burn injury and its relation with myocardial damage

To observe the changes in the expressions of microRNA-126 in myocardial tissue and cardiac troponin I (cTnI) in serum of rats in the early stage of severe burn injury with analysis of their relationship, and to validate the relationship between microRNA-126 and myocardial damage in cellular level. (1) Forty-eight SD rats were divided into sham injury group (n=8, without fluid therapy after sham injury) and burn injury group (n=40, inflicted with 30% TBSA full-thickness scald on the back, hereinafter referred to as burn, and received intraperitoneally injection of lactic acid Ringer's solution) according to the random number table. Blood was collected from abdominal aorta of rats in sham injury group at post injury hour (PIH) 1, and then these 8 rats were sacrificed for obtaining left ventricular tissue. Blood was respectively collected from abdominal aorta of 8 rats in burn injury group at PIH 3, 6, 12, 24, and 48, and then they were sacrificed and the left ventricular tissue was obtained at each time point. The expression of microRNA-126 in myocardial tissue was assessed by real-time fluorescent quantitative RT-PCR. Serum level of cTnI was assessed by ELISA. (2) Rat myocardial cell line H9C2 was divided into normal control group (NC, routinely cultured), stimulation group (S), negative transfection+stimulation group (NT+S), and transfection+stimulation group (T+S) according to the random number table. Cells in S group were treated with hypoxia for 24 h after being cultured with DMEM containing 10% burn serum obtained from rats in burn injury group at PIH 6 in experiment (1). Cells in NT+S group and T+S group were respectively transfected with the negative control of microRNA mimics and microRNA-126 mimics for 24 h, and then were given the same treatment as that of S group. The expression of microRNA-126 in myocardial cells was determined by real-time fluorescent quantitative RT-PCR (with the sample number of 3). Cell counting kit 8 was used to examine the vitality of myocardial cell (with the sample number of 4, denoted as absorbance value). Apoptotic rate of myocardial cells was determined by flow cytometer (with the sample number of 3). Data were processed with one-way analysis of variance and LSD-t test. The relationship between microRNA-126 expression in myocardial tissue and serum level of cTnI of rats was assessed by linear correlation analysis. (1) Compared with that of sham injury group at PIH 1, the expression levels of microRNA-126 in myocardial tissue of rats in burn injury group at PIH 3, 6, 12, 24, and 48 were significantly decreased (with t values from 5.68 to 9.79, P values below 0.01), reaching its nadir at PIH 24 (0.40 ± 0.08). Compared with that of sham injury group at PIH 1, the serum levels of cTnI of rats in burn injury group at PIH 3, 6, 12, 24, and 48 were significantly increased (with t values from 6.68 to 12.79, P values below 0.01), peaking at PIH 12 [(1 035 ± 177) pg/mL]. A significant negative correlation between the expression level of microRNA-126 in myocardial tissue and serum level of cTnI was observed in rats of burn injury group at each time point (r=-0.797, P<0.001). (2) Compared with those of NC group, the microRNA-126 expression levels in myocardial cells of S group and T+S group were respectively decreased and increased (with t values respectively 4.57 and 5.73, P<0.05 or P<0.01), the cell vitality levels were obviously decreased (with t values respectively 14.88 and 6.48, P values below 0.01), and the apoptotic rates were significantly increased (with t values respectively 13.82 and 6.96, P values below 0.01). Compared with that in NT+S group, the microRNA-126 expression level in myocardial cells of T+S group was significantly increased (t=6.77, P<0.01), the cell vitality level was obviously increased (t=8.23, P<0.001), and the apoptotic rate was significantly decreased (t=6.14, P<0.001). Expression level of microRNA-126 in myocardial tissue of rat was decreased in the early stage of severe burn injury. It may participate in regulating myocardial damage and play a protective role.

Fat Grafting in Burn Scar Alleviates Neuropathic Pain via Anti-Inflammation Effect in Scar and Spinal Cord.

Burn-induced neuropathic pain is complex, and fat grafting has reportedly improved neuropathic pain. However, the mechanism of fat grafting in improving neuropathic pain is unclear. Previous investigations have found that neuroinflammation causes neuropathic pain, and anti-inflammatory targeting may provide potential therapeutic opportunities in neuropathic pain. We hypothesized that fat grafting in burn scars improves the neuropathic pain through anti-inflammation. Burn-induced scar pain was confirmed using a mechanical response test 4 weeks after burn injuries, and autologous fat grafting in the scar area was performed simultaneously. After 4 weeks, the animals were sacrificed, and specimens were collected for the inflammation test, including COX-2, iNOS, and nNOS in the injured skin and spinal cord dorsal horns through immunohistochemistry and Western assays. Furthermore, pro-inflammatory cytokines (IL-1 β and TNF-α) in the spinal cord were collected. Double immunofluorescent staining images for measuring p-IκB, p-NFκB, p-JNK, and TUNEL as well as Western blots of AKT, Bax/Bcl-2 for the inflammatory process, and apoptosis were analyzed. Fat grafting significantly reduced COX2, nNOS, and iNOS in the skin and spinal cord dorsal horns, as well as IL-1β and TNF-α, compared with the burn group. Moreover, regarding the anti-inflammatory effect, the apoptosis cells in the spinal cord significantly decreased after the fat grafting in the burn injury group. Fat grafting was effective in treating burn-induced neuropathic pain through the alleviation of neuroinflammation and ameliorated spinal neuronal apoptosis.

The effects of bromelain on angiogenesis, nitric oxide, and matrix metalloproteinase-3 and -9 in rats exposed to electrical burn injury

Abstract This study was aimed to investigate the effects of bromelain on angiogenesis, nitric oxide, and matrix metalloproteinase-3 and -9 in rats exposed to 1200 mV electrical burn injury. Thirty-five, male Wistar albino rats was divided into five groups (n = 7 each), including control (untreated) group; electrical burn injury (EI) group; electrical burn injury + 21.25 mg/kg BW bromelain group (EIB1); electrical burn injury + 42.50 mg/kg BW bromelain group (EIB2); and electrical burn injury + 85.00 mg/kg BW bromelain group (EIB3). Rat models of electrical burns done by providing electricity in rats that had been anesthetized, a voltage of 1200 mV and strong currents 15 mA for 10 s. The VEFG, NO, and MMP-9 levels were significantly greater in the EI group compared to the untreated group. Out of the 21.25 mg/kg BW, 42.50 mg/kg BW, and 85 mg/kg BW doses of Bromelain extract, only the lowest doses prevented EI-induced increase in NO and MMP-9 level (P

Endothelial progenitor cells lowering effect and compensative mechanism in electrical burn injury models of rat

This study aimed to investigate the effects of electrical injury on vascular damage and on matrix metalloproteinase (MMPs) levels. Thirty male Wistar albino rats were divided into five groups (n = 6), including a control group (untreated group), a 600 mv electrical burn injury group, a 900 mv electrical burn injury group, a 1200 mv electrical burn injury group, and a 1500 mv electrical burn injury group. Endothelial progenitor cells (EPCs) and circulating endothelial cells (CECs) were analyzed using flow cytometry. The levels of MMP-9, MMP-3, nitric oxide (NO), vascular endothelial growth factor (VEGF), and vascular cell adhesion molecule (VCAM) were assayed using an enzyme linked immunosorbent assay. Levels of EPCs were significantly lower in all electrical burn injury groups compared with the control group (p < 0.05). The levels of NO and VEGF were significantly increased in all electrical burn injury groups compared with the control group (p < 0.05). The levels of MMP-9 were significantly higher in the 1200 mv electrical burn injury group compared with the control group or the 900 mv electrical burn injury group (p < 0.05). There were no significant differences in MMP-3, VCAM, and CECs levels between groups (p > 0.05). This electrical burn injury model shows a significant decrease in endothelial progenitor cells and an increase in VEGF, NO, and MMP-9 as the compensating mechanism.

Beneficial effects of Morus alba and Azadirachta indica leaf extract based combination cream in scalding type burn injury in rats

Background: The present study was designed to evaluate the potential of a combination cream of aqueous extracts of leaves of Morus alba (MA) and Azadirachta indica (AI) in scalding type burn wound injury in rats. Methods: Plant material was successively extracted and aqueous extracts were selected. Three extract based cream formulations viz. 20% w/w(MA), 20% w/w (AI), and combination cream containing 10%+10% w/w (MA+AI) were prepared. Cream base and standard anti-burn cream containing silver sulfadiazine were also used for comparison. Scalding type burn was given by pouring water at 90°C on a shaved dorsal area of 20 mm 2 . Deep second-degree burn injury was produced which was evaluated for next 21 days for a percentage of wound contraction and period of epithelialization. On 21 st day, animals were sacrificed and histopathological slides were prepared using hematoxylin-eosin staining. Burned tissue was also screened for levels of oxidative stress using thiobarbituric acid reactive substances (TBARS) and glutathione (GSH) estimation. Results: There was a significant increase in the percentage of wound contraction and significant decrease in period of epithelialization in MA, AI, and MA+AI combination cream treated group as compared with control group. However, most significant results were obtained with MA+AI combination cream. Histologically, MA+AI cream treatment resulted in almost complete re-epithelialization and restructuring of the wound tissue. There was a significant rise in TBARS and decrease in GSH levels in burn injury group which was reversed to a major extent by the application of combination cream. Conclusions: The results indicate toward the possible role of free radical scavenging potential of extracts in the Burn wound tissue healing.

A Novel Model of Burn-Blast Combined Injury and Its Phasic Changes of Blood Coagulation in Rats

Burn-blast combined injury has a complex pathological process that may cause adverse complications and difficulties in treatment. This study aims to establish a standard animal model of severe burn-blast combined injury in rats and also to investigate early phasic changes of blood coagulation. By using 54 Wistar rats, distance from explosion source (Hexogen) and size of burned body surface area were determined to induce severe burn-blast combined injury. Thereafter, 256 rats were randomly divided into four groups (n = 64): blast injury group, burn injury group, burn-blast combined injury group, and sham injury group. Gross anatomy and pathological changes in lungs were investigated at 3, 24, 72, and 168 h, respectively. Blood was also collected for analyzing coagulation parameters as prothrombin time, activated partial thromboplastin time, and plasma levels of fibrinogen, D-dimer, antithrombin III, and α2-antiplasmin from 0 to 168 h after injury. Severe burn-blast combined injury was induced by inflicting rats with a moderate blast injury when placing rats 75 cm away from explosion source and a full-thickness burn injury of 25% total body surface area. The rats with burn-blast combined injury had more severe lung injuries when compared with the other three groups. Pathological examination in the BBL group showed diffused alveolar hemorrhage, fluid filling, alveolar atelectasis, rupture and hyperplasia of partial alveolar septum, emphysema-like change, reduced capillary bed, and infiltration of extensive polymorphonuclear cells after injury. The blood of combined injured rats was in a hypercoagulable state within 24 h, shortly restored from 24 to 48 h, and rehypercoagulated from 48 to 72 h after injury. A secondary excessively fibrinolytic function was also found thereafter. The rat model of burn-blast combined injury was successfully established by simulating real explosion characteristics. Rats with burn-blast combined injuries suffered from more severe lung injuries and abnormal coagulation and fibrinolytic function than those induced by a burn injury or a blast injury component. Hence, a time-dependent treatment strategy on coagulation function should be emphasized in clinical therapy of burn-blast combined injury.

Effect of Lidocaine on Reducing Injury in a Rat Electrical Burn Model

Electrical injuries induce progressive tissue loss. We evaluated the effect of lidocaine on tissue necrosis after electrical burn injuries. Forty-two male Wistar albino rats (250-300 g) were divided into 3 groups [Group A (n=6), control group without an electrical burn injury; and Groups B (n=18) and C (n=18), electrical burn injury groups without and with lidocaine therapy, respectively]. Three separate analyses were performed at different time points on 6 of 18 rats from Groups B and C at each time point. Electrical burns were induced by applying 220 V AC between the left upper and right lower extremities for 10 seconds. Myeloperoxidase and malondialdehyde levels were measured in skin and muscle biopsy specimens after the first hour, fresh and dry weight differences in the amputated extremities were calculated after 24 hours, and live and necrotic tissue areas were measured at 7 days after burn injury. We found that lidocaine reduced edema, the number of neutrophils, and neutrophil damage in tissues. We conclude that lidocaine decreased the amount of necrotic tissue caused by electric injury.

Fucoidin, a neutrophil rolling inhibitor, reduces damage in a rat electrical burn injury model

Background Electrical injuries induce progressive tissue loss caused by free oxygen radicals released from neutrophil aggregates. Fucoidin, a potent inhibitor of L-selectin function, reduces the aggregation of neutrophils. The aim of this study was to evaluate the effect of fucoidin on tissue damage in rat electrical burn injury model. Methods Forty-two male Wistar albino rats (250–300 g) were divided into 3 groups (Group A ( n = 6), control group without electrical burn injury; Groups B ( n = 18) and C ( n = 18), electrical burn injury groups without and with fucoidin therapy, respectively). Three separate analyses were performed at different time points on 6 out of 18 mice from Group B and C at each time point. Biochemistry (myeloperoxidase and malondialdehyde levels) and histopathology (number of neutrophils) of the skin and muscle biopsies at 1st hour; tissue edema (ratio of wet weight/dry weight of extremities) at 24th hour; and necrotic areas at 7th day after electrical injury were evaluated. The electrical burn was induced by exposing rats to 220 V AC between their left upper extremity and right lower extremity for 10 s. Fucoidin was administered as 25 mg/kg intravenous bolus injection at 15 min after electrical burn injury. Results Myeloperoxidase and malondialdehyde levels, number of neutrophils, tissue edema, and necrotic area were significantly less in fucoidin-applied rats than the group without fucoidin therapy. Conclusions Fucoidin inhibits tissue damage induced by electrical burn injury in rats by reducing necrotic area, edema and number of neutrophils.

Hydrogen-Rich Saline Protects Against Acute Lung Injury Induced by Extensive Burn in Rat Model

Hydrogen has been reported to selectively quench detrimental reactive oxygen species, particularly hydroxyl radical, and to prevent myocardial or hepatic ischemia/reperfusion injury in multiple models. The aim of this study is to investigate whether hydrogen protects against severe burn-induced acute lung injury in rats. Rats were divided into four groups: sham plus normal saline, burn injury plus normal saline, burn injury plus hydrogen-rich saline, and burn injury plus edaravone. Animals were given full-thickness burn wounds (30% TBSA) using boiling water, except the sham group that was treated with room temperature water. The rats in hydrogen group received 5 ml/kg of hydrogen-rich saline, sham and burn controls obtained the same amount of saline, and the edaravone group was treated with 9 mg/kg of edaravone in saline. Lactated Ringer's solution was given at 6 hours postburn. The lungs were harvested 12 hours postburn for laboratory investigations. Severe burns with delayed resuscitation rapidly caused lung edema and impaired oxygenation in rats. These dysfunctions were ameliorated by administration of hydrogen-rich saline or edaravone. When compared with the burn injury plus normal saline group, hydrogen-rich saline or edaravone group significantly attenuated the pulmonary oxidative products, such as malondialdehyde, carbonyl, and 8-hydroxy-2'-deoxyguanosine. Furthermore, administration of hydrogen-rich saline or edaravone dramatically reduced the pulmonary levels of pulmonary inflammation mediators and myeloperoxidase. Intraperitoneal administration of hydrogen-rich saline improves pulmonary function by reducing oxidative stress and inflammatory response in severe burn-induced acute lung injury.

Early head injury and attention deficit hyperactivity disorder: retrospective cohort study

. Keenan H. T., Hall G. C. &amp; Marshall S.W. ( 2008 ) , 337 , a1984 . DOI:10.1136/bmj.a1984 . Objective To explore the hypothesis that medically attended head injury in young children may be causal in the later development of attention deficit hyperactivity disorder.Design Retrospective cohort study.Setting Health improvement network database (1988–2003), a longitudinal UK general practice dataset.Participants All children registered in the database from birth until their 10th birthday.Main outcome measures Risk of a child with a head injury before age 2 developing attention deficit hyperactivity disorder before age 10 compared with children with a burn injury before age 2 and children with neither a burn nor a head injury.Results Of the 62 088 children who comprised the cohort, 2782 (4.5%) had a head injury and 1116 (1.8%) had a burn injury. The risk of diagnosis of attention deficit hyperactivity disorder before 10 years of age after adjustment for sex, prematurity, socio‐economic status and practice identification number was similar in the head injury (relative risk 1.9, 95% confidence interval 1.5 to 2.5) and burn injury groups (1.7, 1.2 to 2.5) compared with all other children.Discussion Medically attended head injury before 2 years of age does not seem to be causal in the development of attention deficit hyperactivity disorder. Medically attended injury before 2 years of age may be a marker for subsequent diagnosis of attention deficit hyperactivity disorder.

Pulmonary changes in a mouse model of combined burn and smoke inhalation-induced injury

The morbidity and mortality of burn victims increase when burn injury is combined with smoke inhalation. The goal of the present study was to develop a murine model of burn and smoke inhalation injury to more precisely reveal the mechanistic aspects of these pathological changes. The burn injury mouse group received a 40% total body surface area third-degree burn alone, the smoke inhalation injury mouse group received two 30-s exposures of cotton smoke alone, and the combined burn and smoke inhalation injury mouse group received both the burn and the smoke inhalation injury. Animal survival was monitored for 120 h. Survival rates in the burn injury group, the smoke inhalation injury group, and the combined injury group were 70%, 60%, and 30%, respectively. Mice that received combined burn and smoke injury developed greater lung damage as evidenced by histological changes (septal thickening and interstitial edema) and higher lung water content. These mice also displayed more severely impaired pulmonary gas exchange [arterial PO2 (PaO2)/inspired O2 fraction (FiO2)<200]. Lung myeloperoxidase activity was significantly higher in burn and smoke-injured animals compared with the other three experimental groups. Plasma NO2-/NO3-, lung inducible nitric oxide synthase (iNOS) activity, and iNOS mRNA increased with injury; however, the burn and smoke injury group exhibited a higher response. Severity of burn and smoke inhalation injury was associated with more pronounced production of nitric oxide and accumulation of activated leukocytes in lung tissue. The murine model of burn and smoke inhalation injury allows us to better understand pathophysiological mechanisms underlying cardiopulmonary morbidity secondary to burn and smoke inhalation injury.

Early head injury and attention deficit hyperactivity disorder: retrospective cohort study

Objective To explore the hypothesis that medically attended head injury in young children may be causal in the later development of attention deficit hyperactivity disorder.Design Retrospective cohort study.Setting Health improvement...

SKIN NITRIC OXIDE AND ITS METABOLITES ARE INCREASE IN NON-BURNED SKIN AFTER THERMAL INJURIES

Local and systemic inflammation can lead to progression of burn wounds, converting second- to third-degree wounds or extending the burn to adjacent areas. Previous studies have suggested that the skin is an important site of production of nitric oxide (NO), synthesized by inducible nitric oxide synthase (iNOS) activation after injury. NO increases in burned wounds, but its formation in noninjured skin has not been investigated. We hypothesized that after severe burns, NO and cytotoxic peroxynitrite would increase in noninjured skin. We also tested the hypothesis that BBS-2, a specific inhibitor of iNOS, would impair NO formation after burn. Thirteen female sheep were randomized into burn injury and smoke inhalation (n = 5, group 1), burn and smoke treated with BBS-2 (n = 3, group 2), and sham (saline treatment, no injury) (n = 5, group 3). All the animals, including the sham-injury group, were mechanically ventilated for 48 h. Samples of nonburned skin and plasma were collected from each animal, and levels of NO and its metabolites were evaluated using a NO chemiluminescent detector. Nitrotyrosine and iNOS expression were determined in the skin by Immunoperoxidase staining, and scoring of masked slides (epidermis, hair follicles, vessels, glands, and stroma) was performed. Skin NO and metabolites significantly increased in the burn and smoke injury group, and this was inhibited by BBS-2. Nitrotyrosine expression also increased significantly in the skin of burned animals. BBS-2 prevented the increase of NOx but not the increase of nitrotyrosine expression in skin. Plasma levels of NO increased in burned animals when compared with sham, but this increase was not significant. The increase of NO and its metabolites after burn in noninjured skin is followed by a significant increase in peroxynitrite, a potent cytotoxic mediator.

The Changes of Serum Amino Acids after Major Burn and Smoke Inhalation Injuries in Rats

Objective: The mortality rate of patients with cutaneous combined burns with smoke inhalation injury is reported to be much higher than that of patients with either injury alone. Patients with such combined injury need a more intensive and aggressive nutrition supply to help them survive. The present study was designed to test amino acid flux in cases of combined injury (smoke inhalation injury and cutaneous burns). The purpose was to understand the amino acids flux after such combined injury. Methods: Adult male rats were divided 3 groups, non-injury control, smoke inhalation injury and smoke inhalation injury plus cutaneous burns groups. Rats received smoke inhlalation injury with/without major cutaneous thermal injury (40%BSA). Blood was taken from the tail and storaged along with plasma daily for 5 days. Four different amino acids, glutamate, glutamine, arginine and methionine were tested by HPLC and statistically analyzed. Results: Our preliminary results showed that smoke inhalation injury alone did not cause a significant change in amino acids flux during the first 5 days after injury, and the only increase in arginine was observed on the 3rd day after injury (↑ 27~30%, p＞0.05, non-significant). In the cutaneous burn plus smoke inhalation injury group, all four amino acids decreased immediately and significantly. Conclusions: These results suggest that the four non-essential amino acids (glutamine, glutamate, methionine and arginine) are all conditionally essential amino acids in this combined injury (cutaneous burn plus inhalation injuries). However, in the simple smoke inhalation injury group, the amino acids supply was not as important, at least, in the first 5 days after injury.

Heat Stress-Induced Modulation of Host Defense Against Toxoplasma gondii Infection in Mice

This study examined the effects of burn injury on murine immune response against Toxoplasma gondii infection. Male C57BL/6 mice were divided into 3 groups: T. gondii infection (group T), burn injury (group B), and burn injury followed by T. gondii infection (group BT). The survival of group BT was significantly lower than those of group B and group T. Parasite abundance in the tissues was determined by quantitative competitive-polymerase chain reaction. Group BT exhibited significantly higher numbers of T. gondii than group T. Antibody production against T.g.HSP30 in group BT was significantly lower than that in group T, whereas no significant difference was observed in SAG1-specific antibody production. Delayed-type hypersensitivity (DTH) specific for 2,4-dinitrofluorobenzene (DNFB) of both group B and group BT was significantly lower than that of group T. One week after infection, serum interferon-gamma (IFN-gamma) and interleukin (IL)-10 levels in group BT were significantly lower, whereas serum IL-6 levels were significantly higher than in group T Serum TNF-alpha levels in both group T and group BT were elevated at 1 wk after infection, although there was no significant difference between them. Serum IFN-gamma, IL-10, and TNF-alpha levels in group B were not elevated during the experimental term. In conclusion, the impaired antigen-specific antibody production and DTH response, together with the modulated patterns of cytokine responses, seemed to be strongly involved in the development of burn-induced immunosuppression and the consequent increased susceptibility to T. gondii infection in mice.

SKIN NITRIC OXIDE AND ITS METABOLITES ARE INCREASED IN NONBURNED SKIN AFTER THERMAL INJURIES

Local and systemic inflammation can lead to progression of burn wounds, converting second- to third-degree wounds or extending the burn to adjacent areas. Previous studies have suggested that the skin is an important site of production of nitric oxide (NO), synthesized by inducible nitric oxide synthase (iNOS) activation after injury. NO increases in burned wounds, but its formation in noninjured skin has not been investigated. We hypothesized that after severe burns, NO and cytotoxic peroxynitrite would increase in noninjured skin. We also tested the hypothesis that BBS-2, a specific inhibitor of iNOS, would impair NO formation after burn. Thirteen female sheep were randomized into burn injury and smoke inhalation (n = 5, group 1), burn and smoke treated with BBS-2 (n = 3, group 2), and sham (saline treatment, no injury) (n = 5, group 3). All the animals, including the sham-injury group, were mechanically ventilated for 48 h. Samples of nonburned skin and plasma were collected from each animal, and levels of NO and its metabolites were evaluated using a NO chemiluminescent detector. Nitrotyrosine and iNOS expression were determined in the skin by Immunoperoxidase staining, and scoring of masked slides (epidermis, hair follicles, vessels, glands, and stroma) was performed. Skin NO and metabolites significantly increased in the burn and smoke injury group, and this was inhibited by BBS-2. Nitrotyrosine expression also increased significantly in the skin of burned animals. BBS-2 prevented the increase of NOx but not the increase of nitrotyrosine expression in skin. Plasma levels of NO increased in burned animals when compared with sham, but this increase was not significant. The increase of NO and its metabolites after burn in noninjured skin is followed by a significant increase in peroxynitrite, a potent cytotoxic mediator.

D-Tubocurarine Accentuates the Burn-Induced Upregulation of Nicotinic Acetylcholine Receptors at the Muscle Membrane

BACKGROUND Increases in acetylcholine receptors (AChRs) at the muscle membrane, induced by burn injury, have been associated with a hyperkalemic response to succinylcholine and resistance to d-tubocurarine-like drugs. Muscle relaxants often are administered to burn-injured patients in the intensive care unit to facilitate mechanical ventilation. This study in rats tested whether continuous administration of d-tubocurarine in subparalytic doses exaggerates the upregulation of AChRs induced by burn trauma. Subparalytic doses were used to avoid the confounding effects of immobilization. METHODS Three days after an approximate 50% body surface area burn or sham injury, the animals received an infusion of 3.03 +/- 0.05 micrograms/h of d-tubocurarine or equal volume of saline directly to the left gastrocnemius muscle via catheter connected to a subcutaneously implanted osmotic pump. After 7 days of d-tubocurarine or saline infusion, the AChRs were quantitated using 125I-alpha-bungarotoxin. The AChRs on the d-tubocurarine or saline-infused left gastrocnemius were compared to the contralateral gastrocnemius in the same group. The right or left gastrocnemius AChRs were compared to the ipsilateral muscles between groups. These intra- and intergroup comparisons allowed the delineation of the effects of catheter irritation, burns, or d-tubocurarine on AChRs. RESULTS Daily examination of the withdrawal response to toe-pinch revealed no evidence of paralysis. Weight loss in the burn-injury animals receiving d-tubocurarine or saline was similar, confirming that the infusion of d-tubocurarine did not impair the mobility of the animals to move and feed. The plasma d-tubocurarine concentration after 7 days of infusion was 26.0 +/- 12 ng/ml (mean +/- SE). Regardless of burn or sham injury or of d-tubocurarine or saline infusion, the concentration of AChRs on the left was consistently greater than in the contralateral right gastrocnemius muscles within the same group, indicating that manipulation of the area alone can result in upregulation of AChRs. The AChRs in the right gastrocnemius of burn-injured animals were greater than those in the same muscle of sham-injured animals, regardless of saline (7.24 +/- 0.9 vs. 5.7 +/- 0.5 fmoles/mg protein, P = 0.06) or d-tubocurarine (7.3 +/- 0.4 vs. 5.7 +/- 0.5, P < 0.05) infusion to the burn-injury groups. AChRs in the left gastrocnemius of burn-injury animals receiving d-tubocurarine were significantly greater than those in burn- or sham-injury animals receiving saline (13.9 +/- 1.1 vs. 9.8 +/- 1.2 and 7.1 +/- 0.5 fmoles/mg protein, respectively, P < 0.05). CONCLUSIONS Burn-induced upregulation of AChRs is accentuated by infusion of subparalytic doses of d-tubocurarine. Concomitant administration of d-tubocurarine to burn-injured patients may result in further exaggeration of the aberrant responses to neuromuscular relaxants.

Oxygen Free Radicals Contribute to Postburn Cardiac Cell Membrane Dysfunction

This study evaluated the contribution of O2free radicals to changes in cardiac function after burn injury. Full-thickness scald burns comprising 42% of the total body surface area were produced in rats. Mean arterial pressure, heart rate, pH, cardiac transmembrane potential (Ling Gerard electrode, Em), myocardial ATP, creatine phosphate (CP), glucose 6-phosphate, and lactate were measured enzymatically 24 hr postburn in four groups: Group 1, sham burn controls,N= 12; Group 2, untreated burn injury,N= 14; Group 3,N= 10, burn injury resuscitated with Ringer's lactate (Parkland formula); Group 4, burns pretreated with oral allopurinol (10 mg/kg) for 5 days before burn injury,N= 11.In vitrocardiac contractile function was assessed 24 hr after burn injury in additional animals (N= 8) from each of the four experimental groups. Untreated burn injury caused hypotension, bradycardia, depolarization of the cardiac cell membrane (Em fell from 78.5 ± 0.4 to 66.8 ± 0.4,P< 0.05), and left ventricular contractile depression despite no significant fall in cardiac ATP content. In contrast, cardiac tissue CP fell and myocardial tissue lactate rose. Allopurinol pretreatment oblated burn-induced hypotension, bradycardia, and cardiac cell membrane depolarization and improved cardiac contractile function despite no fluid resuscitation from burn injury. In contrast, aggressive fluid resuscitation from burn injury (Group 3) repolarized cardiac cell membrane but did not reverse burn-induced cardiac contractile deficits. These data suggest that xanthine oxidase-mediated free radical production contributes, in part, to postburn alterations in cardiac function.

D-Tubocurarine accentuates the burn-induced upregulation of nicotinic acetylcholine receptors at the muscle membrane.

Increases in acetylcholine receptors (AChRs) at the muscle membrane, induced by burn injury, have been associated with a hyperkalemic response to succinylcholine and resistance to d-tubocurarine-like drugs. Muscle relaxants often are administered to burn-injured patients in the intensive care unit to facilitate mechanical ventilation. This study in rats tested whether continuous administration of d-tubocurarine in subparalytic doses exaggerates the upregulation of AChRs induced by burn trauma. Subparalytic doses were used to avoid the confounding effects of immobilization. Three days after an approximate 50% body surface area burn or sham injury, the animals received an infusion of 3.03 +/- 0.05 micrograms/h of d-tubocurarine or equal volume of saline directly to the left gastrocnemius muscle via catheter connected to a subcutaneously implanted osmotic pump. After 7 days of d-tubocurarine or saline infusion, the AChRs were quantitated using 125I-alpha-bungarotoxin. The AChRs on the d-tubocurarine or saline-infused left gastrocnemius were compared to the contralateral gastrocnemius in the same group. The right or left gastrocnemius AChRs were compared to the ipsilateral muscles between groups. These intra- and intergroup comparisons allowed the delineation of the effects of catheter irritation, burns, or d-tubocurarine on AChRs. Daily examination of the withdrawal response to toe-pinch revealed no evidence of paralysis. Weight loss in the burn-injury animals receiving d-tubocurarine or saline was similar, confirming that the infusion of d-tubocurarine did not impair the mobility of the animals to move and feed. The plasma d-tubocurarine concentration after 7 days of infusion was 26.0 +/- 12 ng/ml (mean +/- SE). Regardless of burn or sham injury or of d-tubocurarine or saline infusion, the concentration of AChRs on the left was consistently greater than in the contralateral right gastrocnemius muscles within the same group, indicating that manipulation of the area alone can result in upregulation of AChRs. The AChRs in the right gastrocnemius of burn-injured animals were greater than those in the same muscle of sham-injured animals, regardless of saline (7.24 +/- 0.9 vs. 5.7 +/- 0.5 fmoles/mg protein, P = 0.06) or d-tubocurarine (7.3 +/- 0.4 vs. 5.7 +/- 0.5, P < 0.05) infusion to the burn-injury groups. AChRs in the left gastrocnemius of burn-injury animals receiving d-tubocurarine were significantly greater than those in burn- or sham-injury animals receiving saline (13.9 +/- 1.1 vs. 9.8 +/- 1.2 and 7.1 +/- 0.5 fmoles/mg protein, respectively, P < 0.05). Burn-induced upregulation of AChRs is accentuated by infusion of subparalytic doses of d-tubocurarine. Concomitant administration of d-tubocurarine to burn-injured patients may result in further exaggeration of the aberrant responses to neuromuscular relaxants.

Chronic Ethanol Intake and Burn Injury

Chronic ethanol (EtOH) intake and injury are both associated with increased susceptibility to infection in the host. This study examined the immune and gastrointestinal alterations induced by chronic EtOH intake and injury, and compared the effects of enteral and intravenous administration of EtOH. Rats received 20% EtOH daily for 14 days by gavage [oral (PO)] or superior vena cava [intravenous (i.v.)] infusion. Mean blood EtOH concentrations at 90 minutes after administration were 95.3 mg/dL (PO) and 94.4 mg/dL (i.v.). An additional group of animals underwent a 30% total body surface area full-thickness burn injury 4 hours after the final dose of EtOH or normal saline on experimental day 14. All animals were killed 4 days after burn injury. Nonadherent splenic lymphocytes were tested for mitogenic responses to the T-cell mitogens concanavalin A (ConA) and phytohemagglutinin (PHA), and the B-cell mitogens lipopolysaccharide (LPS) and pokeweed. Quantitative bacterial cultures of mesenteric lymph nodes and liver were also performed. Alterations of intestinal mucosa were determined by measurement of ileal mucosal weight, DNA, protein, and diamine oxidase content. Circulating plasma endotoxin concentrations were also measured. Chronic PO-EtOH intake induced a significant impairment in mitogenic response to T-cell mitogens, with a fourfold reduction in ConA and a twofold reduction in PHA response (p < 0.05 by analysis of variance) and increased bacterial translocation (70% vs. 10%). Chronic EtOH administered by the i.v. route did not reduce mitogenic response to any of the mitogens studied. Histologic examination of ileal segments demonstrated that chronic PO-EtOH administration was associated with significant mucosal disruption and exfoliation. Chronic administration of PO-EtOH prior to burn injury induced a significant impairment in spleen mitogenic response to ConA, PHA, and LPS when compared with all other burn injury groups. Chronic administration of EtOH by the i.v. route prior to burn injury did not alter splenic mitogenesis. In addition, chronic PO-EtOH prior to burn injury increased bacterial translocation rates (80% vs. 33%) and prevented the normal intestinal reparative response to burn injury (demonstrated by a significant reduction in ileal mucosal weight, DNA, and diamine oxidase content). Enteral but not i.v. administration of EtOH induced significant immunologic dysfunction (demonstrated by altered spleen mitogenic response) and gastrointestinal dysfunction (demonstrated by depressed ileal mucosal weight, DNA, and diamine oxidase content, and increased bacterial translocation rates). In addition, the administration of chronic enteral EtOH prior to injury resulted in significant immune suppression and impaired the host's ability for normal intestinal repair. These results suggest that this EtOH-induced reduction in immunocompetence may be gut-mediated and that the administration of alcohol prior to injury may result in a synergistic alteration of gut and immune integrity.