Role of calcitonin gene-related peptide (CGRP) in ovine burn and smoke inhalation injury

Metabolic and toxicological considerations regarding CGRP mAbs and CGRP antagonists to treat migraine in COVID-19 patients: a narrative review

INTRODUCTION

Migraine pharmacological therapies targeting calcitonin gene-related peptide (CGRP), including monoclonal antibodies and gepants, have shown clinical effect and optimal tolerability. Interactions between treatments of COVID-19 and CGRP-related drugs have not been reviewed.

AREAS COVERED

An overview of CGRP, a description of the characteristics of each CGRP-related drug and its response predictors, COVID-19 and its treatment, the interactions between CGRP-related drugs and COVID-19 treatment, COVID-19 and vaccination-induced headache, and the neurological consequences of Covid-19.

EXPERT OPINION

Clinicians should be careful about using gepants for COVID-19 patients, due to the potential drug interactions with drugs metabolized via CYP3A4 cytochrome. In particular, COVID-19 treatment (especially nirmatrelvir packaged with ritonavir, as Paxlovid) should be considered cautiously. It is advisable to stop or adjust the dose (10 mg atogepant when used for episodic migraine) of gepants when using Paxlovid (except for zavegepant). CGRP moncolconal antibodies (CGRP-mAbs) do not have drug - drug interactions, but a few days' interval between a COVID-19 vaccination and the use of CGRP mAbs is recommended to allow the accurate identification of the possible adverse effects, such as injection site reaction. Covid-19- and vaccination-related headache are known to occur. Whether CGRP-related drugs would be of benefit in these circumstances is not yet known.

Calcitonin Gene-Related Peptide Monoclonal Antibodies and Risk of SARS-CoV-2 Infection and Severe COVID-19 Outcomes Among Veterans With Migraine Disorder

Importance

Calcitonin gene-related peptide (CGRP), a neuropeptide involved in migraine pathophysiology, is also a key neuroimmune modulator. CGRP antagonists may help mitigate the hyperinflammatory response observed in patients with COVID-19; however, findings from the literature are contradictory, and to date, no study has investigated the safety and effectiveness of CGRP antagonists against COVID-19.

Objective

To evaluate the association between CGRP monoclonal antibody (mAb) treatment and risk of SARS-CoV-2 infection and sequela hospitalization, requiring supplemental oxygen, use of mechanical ventilation, or death.

Design, Setting, and Participants

This retrospective cohort study analyzed the electronic health records of US veterans aged 18 to 65 years who were diagnosed with migraine disorder and were at risk of COVID-19 between January 20, 2020, and May 19, 2022.

Exposure

Initiation of CGRP mAbs.

Main Outcomes and Measures

The main outcome was cumulative incidence of SARS-CoV-2 infection. Odds of 30-day hospitalization, requiring supplemental oxygen, use of mechanical ventilation, or death were secondary outcomes.

Results

Among 8 178 652 eligible person-trials (354 294 veterans), 9992 (mean [SD] age, 46.0 [9.5] years; 53.9% male) initiated CGRP mAbs and 8 168 660 (mean [SD] age, 46.6 [10.2] years; 65.7% male) did not initiate CGRP mAbs. Over a 28-month follow-up period, 1247 initiators (12.5%) and 780 575 noninitiators (9.6%) tested positive for SARS-CoV-2. After censoring persons who deviated from treatment, the incidence was 7.4 cases per 1000 person-months among initiators and 6.9 per 1000 person-months among noninitiators. The inverse probability-weighted observational analogs of intention-to-treat and per-protocol hazard ratios were 0.95 (95% CI, 0.89-1.01) and 0.93 (95% CI, 0.86-1.02), respectively. No significant differences in the likelihood of hospitalization (odds ratio [OR], 0.93; 95% CI, 0.62-1.41), requiring supplemental oxygen (OR, 0.77; 95% CI, 0.45-1.30), use of mechanical ventilation (OR, 0.85; 95% CI, 0.26-2.84), or death (OR, 0.67; 95% CI, 0.09-5.23) were observed between CGRP mAb initiators and noninitiators who tested positive for SARS-CoV-2.

Conclusions and Relevance

In this cohort study, CGRP mAb treatment was not associated with positive SARS-CoV-2 test results or risk of severe COVID-19 outcomes, suggesting that CGRP mAbs may be used for migraine prevention during the COVID-19 pandemic. Given the few events of requiring supplemental oxygen, use of mechanical ventilation, and death, replication analysis in a larger sample of patients later in the course of disease is warranted.

CGRP physiology, pharmacology, and therapeutic targets: migraine and beyond

Calcitonin gene-related peptide (CGRP) is a neuropeptide with diverse physiological functions. Its two isoforms (α and β) are widely expressed throughout the body in sensory neurons as well as in other cell types, such as motor neurons and neuroendocrine cells. CGRP acts via at least two G protein-coupled receptors that form unusual complexes with receptor activity-modifying proteins. These are the CGRP receptor and the AMY1 receptor; in rodents, additional receptors come into play. Although CGRP is known to produce many effects, the precise molecular identity of the receptor(s) that mediates CGRP effects is seldom clear. Despite the many enigmas still in CGRP biology, therapeutics that target the CGRP axis to treat or prevent migraine are a bench-to-bedside success story. This review provides a contextual background on the regulation and sites of CGRP expression and CGRP receptor pharmacology. The physiological actions of CGRP in the nervous system are discussed, along with updates on CGRP actions in the cardiovascular, pulmonary, gastrointestinal, immune, hematopoietic, and reproductive systems and metabolic effects of CGRP in muscle and adipose tissues. We cover how CGRP in these systems is associated with disease states, most notably migraine. In this context, we discuss how CGRP actions in both the peripheral and central nervous systems provide a basis for therapeutic targeting of CGRP in migraine. Finally, we highlight potentially fertile ground for the development of additional therapeutics and combinatorial strategies that could be designed to modulate CGRP signaling for migraine and other diseases.

5-HT/CGRP pathway and Sumatriptan role in Covid-19

Coronavirus disease 2019 (Covid-19) is a pandemic caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). In Covid-19, there is uncontrolled activation of immune cells with a massive release of pro-inflammatory cytokines and the development of cytokine storm. These inflammatory changes induce impairment of different organ functions, including the central nervous system (CNS), leading to acute brain injury and substantial changes in the neurotransmitters, including serotonin (5-HT) and calcitonin gene-related peptide (CGRP), which have immunomodulatory properties through modulation of central and peripheral immune responses. In Covid-19, 5-HT neurotransmitters and CGRP could contribute to abnormal and atypical vascular reactivity. Sumatriptan is a pre-synaptic 5-HT (5-HT1D and 5-HT1B) agonist and inhibits the release of CGRP. Both 5-HT and CGRP seem to be augmented in Covid-19 due to underlying activation of inflammatory signaling pathways and hyperinflammation. In virtue of its anti-inflammatory and antioxidant properties with inhibition release of 5-HT and CGRP, Sumatriptan may reduce Covid-19 hyperinflammation. Therefore, Sumatriptan might be a novel potential therapeutic strategy in managing Covid-19. In conclusion, Sumatriptan could be an effective therapeutic strategy in managing Covid-19 through modulation of 5-HT neurotransmitters and inhibiting CGRP.

Vasoactive Peptides: Role in COVID-19 Pathogenesis and Potential Use as Biomarkers and Therapeutic Targets

BACKGROUND

The ongoing outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as the latest threat to global health, causes overwhelming effects for the public healthcare systems worldwide. Of note, in addition to the respiratory complications, some patients with coronavirus disease 2019 (COVID-19) also develop serious cardiovascular injuries. Vasoactive peptides play an important role in a wide range of physiological and pathological conditions.

AIM

With the urgent need for exploring the specific therapeutic targets and biomarkers for the emerging COVID-19, the general aim of this review is to discuss the potentials of the vasoactive peptides including Angiotensin II (Ang II), vasoactive intestinal peptide (VIP), endothelin-1 (ET-1), calcitonin gene-related peptide (CGRP), natriuretic peptides, substance P (SP) and bradykinin (BK) as therapeutic targets and/or prognostic indicators for the COVID-19 pandemic.

CONCLUSION

Based on various observations some authors conclude that the assessment of vasoactive peptides shall be considered a routine part of COVID-19 patient monitoring, and they can serve as potential therapeutic targets for the disease management.

Identification of FDA approved drugs against SARS-CoV-2 RNA dependent RNA polymerase (RdRp) and 3-chymotrypsin-like protease (3CLpro), drug repurposing approach

The RNA-dependent RNA polymerase (RdRp) and 3C-like protease (3CLpro) from SARS-CoV-2 play crucial roles in the viral life cycle and are considered the most promising targets for drug discovery against SARS-CoV-2. In this study, FDA-approved drugs were screened to identify the probable anti-RdRp and 3CLpro inhibitors by molecular docking approach. The number of ligands selected from the PubChem database of NCBI for screening was 1760. Ligands were energy minimized using Open Babel. The RdRp and 3CLpro protein sequences were retrieved from the NCBI database. For Homology Modeling predictions, we used the Swiss model server. Their structure was then energetically minimized using SPDB viewer software and visualized in the CHIMERA UCSF software. Molecular dockings were performed using AutoDock Vina, and candidate drugs were selected based on binding affinity (∆G). Hydrogen bonding and hydrophobic interactions between ligands and proteins were visualized using Ligplot and the Discovery Studio Visualizer v3.0 software. Our results showed 58 drugs against RdRp, which had binding energy of − 8.5 or less, and 69 drugs to inhibit the 3CLpro enzyme with a binding energy of − 8.1 or less. Six drugs based on binding energy and number of hydrogen bonds were chosen for the next step of molecular dynamics (MD) simulations to investigate drug-protein interactions (including Nilotinib, Imatinib and dihydroergotamine for 3clpro and Lapatinib, Dexasone and Relategravir for RdRp). Except for Lapatinib, other drugs-complexes were stable during MD simulation. Raltegravir, an anti-HIV drug, was observed to be the best compound against RdRp based on docking binding energy (− 9.5 kcal/mole) and MD results. According to the MD results and binding energy, dihydroergotamine is a suitable candidate for 3clpro inhibition (− 9.6 kcal/mol). These drugs were classified into several categories, including antiviral, antibacterial, anti-inflammatory, anti-allergic, cardiovascular, anticoagulant, BPH and impotence, antipsychotic, antimigraine, anticancer, and so on. The common prescription-indications for some of these medication categories appeared somewhat in line with manifestations of COVID-19. We hope that they can be beneficial for patients with certain specific symptoms of SARS-CoV-2 infection, but they can also probably inhibit viral enzymes. We recommend further experimental evaluations in vitro and in vivo on these FDA-approved drugs to assess their potential antiviral effect on SARS-CoV-2.

CGRP Receptor Antagonism in COVID-19: Potential Cardiopulmonary Adverse Effects

Recently, the US FDA has authorized a drug repurposing trial with calcitonin gene-related peptide (CGRP) receptor antagonists to reduce lung inflammation in coronavirus 2019 (COVID-19). However, the well-established cardiopulmonary protective effects of CGRP raise concerns about the safety of antagonizing CGRP in COVID-19. Awareness regarding potential cardiopulmonary adverse effects may enable their early detection and prevent illness from worsening.

Assessment and treatment of acute toxic inhalations

PURPOSE OF REVIEW

Acute toxic inhalation exposures affect thousands of individuals worldwide each year. The acute evaluation of these inhaled exposures is often fraught with difficulty in identifying a specific agent, may involve multiple compounds, and a wide variety of responses are seen depending on the physical properties of the specific toxicant, the length of time of inhalation, and the concentration of the exposure. Recognizing key aspects of the most common acute toxic inhalations is useful in developing a diagnosis and treatment strategy.

RECENT FINDINGS

Use of sequential observations with flexible bronchoscopy has been the standard of care for assessing airway injury, and virtual bronchoscopy using computed tomographic images in a three-dimensional reconstructed image can now better identify airway narrowing. Use of [F]-fluorodeoxyglucose uptake, as measured by PET, has the potential for early recognition of delayed acute lung injury in toxic inhalation exposures. Development of a standardized respiratory injury grading system is ongoing with a recent multicenter trial nearly complete, allowing for more accurate estimates of eventual outcomes and guide levels of intensity of care for patients with acute inhalation injury. Removal from the source of exposure and airway support remain the first critical aspect of treatment, and additional therapies have been studied recently that focus on altering molecular mechanisms of acute cellular injury, expanding potential treatments beyond other pharmacotherapeutic strategies utilized previously such as mucolytics, bronchodilators, and inhaled anticoagulants.

SUMMARY

Although a prevalent source of airway injury, exposure to acute toxic inhalants is often difficult to assess and prognosticate, and challenging to treat.

Inhalation Injury in the Burned Patient

Inhalation injury causes a heterogeneous cascade of insults that increase morbidity and mortality among the burn population. Despite major advancements in burn care for the past several decades, there remains a significant burden of disease attributable to inhalation injury. For this reason, effort has been devoted to finding new therapeutic approaches to improve outcomes for patients who sustain inhalation injuries.The three major injury classes are the following: supraglottic, subglottic, and systemic. Treatment options for these three subtypes differ based on the pathophysiologic changes that each one elicits.Currently, no consensus exists for diagnosis or grading of the injury, and there are large variations in treatment worldwide, ranging from observation and conservative management to advanced therapies with nebulization of different pharmacologic agents.The main pathophysiologic change after a subglottic inhalation injury is an increase in the bronchial blood flow. An induced mucosal hyperemia leads to edema, increases mucus secretion and plasma transudation into the airways, disables the mucociliary escalator, and inactivates hypoxic vasocontriction. Collectively, these insults potentiate airway obstruction with casts formed from epithelial debris, fibrin clots, and inspissated mucus, resulting in impaired ventilation. Prompt bronchoscopic diagnosis and multimodal treatment improve outcomes. Despite the lack of globally accepted standard treatments, data exist to support the use of bronchoscopy and suctioning to remove debris, nebulized heparin for fibrin casts, nebulized N-acetylcysteine for mucus casts, and bronchodilators.Systemic effects of inhalation injury occur both indirectly from hypoxia or hypercapnia resulting from loss of pulmonary function and systemic effects of proinflammatory cytokines, as well as directly from metabolic poisons such as carbon monoxide and cyanide. Both present with nonspecific clinical symptoms including cardiovascular collapse. Carbon monoxide intoxication should be treated with oxygen and cyanide with hydroxocobalamin.Inhalation injury remains a great challenge for clinicians and an area of opportunity for scientists. Management of this concomitant injury lags behind other aspects of burn care. More clinical research is required to improve the outcome of inhalation injury.The goal of this review is to comprehensively summarize the diagnoses, treatment options, and current research.

Difficulties in modelling ARDS (2017 Grover Conference Series)

Fifty years after the first description of acute respiratory distress syndrome (ARDS), none of the many positive drug studies in animal models have been confirmed in clinical trials and translated into clinical practice. This bleak outcome of so many animal experiments shows how difficult it is to model ARDS. Lungs from patients are characterized by hyperinflammation, permeability edema, and hypoxemia; accordingly, this is what most models aim to reproduce. However, in animal models it is very easy to cause inflammation in the lungs, but difficult to cause hypoxemia. Often - and not unlike in patients - models with hypoxemia are accompanied by cardiovascular failure that necessitates fluid support and ventilation, raising the question as to the role of intensive care measures in models of ARDS. In our opinion, there are two major arguments in favor of modelling intensive care medicine in models of ARDS: (1) preventing death from shock; and (2) modelling ventilation and other ICU measures as a second hit. The preferable predictive endpoints in any model of ARDS remain unclear. At present, the best recommendation is to use endpoints that can be compared across studies (i.e. PaO₂/FiO₂ ratio, compliance, wet-to-dry weight ratio) rather than percentage data. Another important and often overlooked issue is the fact that the thermoneutral environmental temperatures for mice and rats are 30℃ and 28℃, respectively; thus, at room temperature (20-22℃) they suffer from cold stress with the associated significant metabolic changes. While, by definition, any model is an abstraction, we suggest that clinically relevant models of ARDS will have to closer recapitulate important properties of the disease while taking into account species-specific confounders.

The Role of Neurogenic Inflammation in Blood-Brain Barrier Disruption and Development of Cerebral Oedema Following Acute Central Nervous System (CNS) Injury

Acute central nervous system (CNS) injury, encompassing traumatic brain injury (TBI) and stroke, accounts for a significant burden of morbidity and mortality worldwide, largely attributable to the development of cerebral oedema and elevated intracranial pressure (ICP). Despite this, clinical treatments are limited and new therapies are urgently required to improve patient outcomes and survival. Originally characterised in peripheral tissues, such as the skin and lungs as a neurally-elicited inflammatory process that contributes to increased microvascular permeability and tissue swelling, neurogenic inflammation has now been described in acute injury to the brain where it may play a key role in the secondary injury cascades that evolve following both TBI and stroke. In particular, release of the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) appear to be critically involved. In particular, increased SP expression is observed in perivascular tissue following acute CNS injury, with the magnitude of SP release being related to both the frequency and degree of the insult. SP release is associated with profound blood-brain barrier disruption and the subsequent development of vasogenic oedema, as well as neuronal injury and poor functional outcomes. Inhibition of SP through use of a neurokinin 1 (NK1) antagonist is highly beneficial following both TBI and ischaemic stroke in pre-clinical models. The role of CGRP is more unclear, especially with respect to TBI, with both elevations and reductions in CGRP levels reported following trauma. However, a beneficial role has been delineated in stroke, given its potent vasodilatory effects. Thus, modulating neuropeptides represents a novel therapeutic target in the treatment of cerebral oedema following acute CNS injury.

Pathophysiology, research challenges, and clinical management of smoke inhalation injury

Smoke inhalation injury is a serious medical problem that increases morbidity and mortality after severe burns. However, relatively little attention has been paid to this devastating condition, and the bulk of research is limited to preclinical basic science studies. Moreover, no worldwide consensus criteria exist for its diagnosis, severity grading, and prognosis. Therapeutic approaches are highly variable depending on the country and burn centre or hospital. In this Series paper, we discuss understanding of the pathophysiology of smoke inhalation injury, the best evidence-based treatments, and challenges and future directions in diagnostics and management.

Diagnosis and management of inhalation injury: an updated review

In this article we review recent advances made in the pathophysiology, diagnosis, and treatment of inhalation injury. Historically, the diagnosis of inhalation injury has relied on nonspecific clinical exam findings and bronchoscopic evidence. The development of a grading system and the use of modalities such as chest computed tomography may allow for a more nuanced evaluation of inhalation injury and enhanced ability to prognosticate. Supportive respiratory care remains essential in managing inhalation injury. Adjuncts still lacking definitive evidence of efficacy include bronchodilators, mucolytic agents, inhaled anticoagulants, nonconventional ventilator modes, prone positioning, and extracorporeal membrane oxygenation. Recent research focusing on molecular mechanisms involved in inhalation injury has increased the number of potential therapies.

Calcitonin gene-related peptide: physiology and pathophysiology

Calcitonin gene-related peptide (CGRP) is a 37-amino acid neuropeptide. Discovered 30 years ago, it is produced as a consequence of alternative RNA processing of the calcitonin gene. CGRP has two major forms (α and β). It belongs to a group of peptides that all act on an unusual receptor family. These receptors consist of calcitonin receptor-like receptor (CLR) linked to an essential receptor activity modifying protein (RAMP) that is necessary for full functionality. CGRP is a highly potent vasodilator and, partly as a consequence, possesses protective mechanisms that are important for physiological and pathological conditions involving the cardiovascular system and wound healing. CGRP is primarily released from sensory nerves and thus is implicated in pain pathways. The proven ability of CGRP antagonists to alleviate migraine has been of most interest in terms of drug development, and knowledge to date concerning this potential therapeutic area is discussed. Other areas covered, where there is less information known on CGRP, include arthritis, skin conditions, diabetes, and obesity. It is concluded that CGRP is an important peptide in mammalian biology, but it is too early at present to know if new medicines for disease treatment will emerge from our knowledge concerning this molecule.

Multiple versus single injections of fluorescent microspheres for the determination of regional organ blood flow in septic sheep

Determination of regional blood flow by the injection of microspheres in sepsis models is crucial for the experimental evaluation of the influence of experimental treatment strategies on organ perfusion. However, multiple injections may critically increase the total quantity of microspheres, thereby restricting regional microcirculation and altering the results of blood flow measurements. This study was designed to compare the results of multiple versus single injections of microspheres in an established ovine sepsis model. Injury was induced by smoke inhalation and instillation of Pseudomonas aeruginosa into the lungs. Twenty sheep were studied for 4, 8, 12, 18, or 24 h, respectively. Microspheres were injected at the end of the study period and the animals were euthanized and organ tissues were harvested. Another four sheep were studied for 24 h and multiple microsphere injections were performed at the above indicated time points in the same animals. Tracheal blood flow significantly increased and blood flow to the pancreas and ileum significantly decreased versus baseline in both groups (P < 0.05 each). Blood flow to the ileum, renal cortex and skin did not significantly change versus baseline in both groups (P > 0.05). Blood flow was higher to the trachea in the multiple injection group at 18 h (P = 0.048) and to the ileum at 12 h (P = 0.049), and lower to the skin at 18 h (P = 0.015). In conclusion, the results indicate that multiple versus single microsphere injections induced no or negligible alterations during ovine sepsis. This finding may help reduce the quantity of animals needed in future experiments.

Administration of a peroxynitrite decomposition catalyst into the bronchial artery attenuates pulmonary dysfunction after smoke inhalation and burn injury in sheep

Reactive nitrogen species such as peroxynitrite play a significant role in burn and smoke inhalation injury. The bronchial circulation increases more than 10-fold in response to this combination injury. We hypothesized that direct delivery of low-dose WW-85, a peroxynitrite decomposition catalyst, into the bronchial artery would attenuate burn- and smoke inhalation-induced acute lung injury. In adult female sheep (n = 17), the bronchial artery was cannulated in preparation surgery. After a 5- to 7-day recovery period, sheep were subjected to a burn (40% total body surface area, third degree) and inhalation injury (48 breaths of cotton smoke, <40°C). The animals were divided into three groups following the injury: (i) WW-85 group: 1 h after injury, WW-85 (0.002 mg/kg per hour) was continuously infused into the bronchial artery, n = 5; (ii) control group: 1 h after injury, an equivalent amount of saline was injected into the bronchial artery, n = 6; (iii) sham group: no injury, no treatment, same operation and anesthesia, n = 6. All animals were mechanically ventilated and fluid resuscitated equally. In the control group, the injury induced a severe deterioration of pulmonary oxygenation and shunting and an increase in pulmonary microvascular permeability toward sham. The injury was further associated with an increase in reactive nitrogen species in lung tissues of the control group. All these alterations were significantly attenuated in the WW-85 group. We demonstrated that a low dosage of WW-85 directly administered into the bronchial artery attenuated pulmonary dysfunction to the same extent as higher systemically administered doses in previous experiments. Our data strongly suggest that local airway production of peroxynitrite contributes to pulmonary dysfunction following smoke inhalation and burn injury.

Inflammatory role of AMP-activated protein kinase signaling in an experimental model of toxic smoke inhalation injury

OBJECTIVE

The molecular mechanisms underlying lung inflammation in toxic smoke inhalation injury are unknown. We investigated the signaling pathway responsible for the induction of interleukin 8 by wood smoke extract in lung epithelial cells and lung inflammation induced by wood smoke exposure in mice.

DESIGN

A randomized, controlled study.

SETTING

A research laboratory.

INTERVENTIONS AND MAIN RESULTS

Exposure of primary human bronchial epithelial cells to wood smoke extract sequentially activated NADPH oxidase and increased intracellular reactive oxygen species level; activated AMP-activated protein kinase, extracellular signal-regulated kinase and Jun N-terminal kinase (two mitogen-activated protein kinases), and nuclear factor-κB and signal transducer and activator of transcription protein 3 (two transcription factors); and induced interleukin-8. Inhibition of NADPH oxidase activation with apocynin or siRNA targeting p47(phox ) (a subunit of NADPH oxidase) attenuated the increased intracellular reactive oxygen species level, AMP-activated protein kinase activation, and interleukin-8 induction. Removal of intracellular reactive oxygen species by N-acetyl-cysteine reduced the activation of AMP-activated protein kinase, extracellular signal-regulated kinase and Jun N-terminal kinase, and interleukin-8 induction. Prevention of AMP-activated protein kinase activation by Compound C or AMP-activated protein kinase siRNA lessened the activation of Jun N-terminal kinase, extracellular signal-regulated kinase, nuclear factor-κB, signal transducer and activator of transcription protein 3 and interleukin-8 induction. Inhibition of Jun N-terminal kinase and extracellular signal-regulated kinase activation by inhibitors reduced the activation of nuclear factor-κB and signal transducer and activator of transcription protein 3 and interleukin-8 induction. Abrogation of nuclear factor-κB and signal transducer and activator of transcription protein 3 activation by inhibitors attenuated the interleukin-8 induction. Additionally, acute exposure of mice to wood smoke promoted AMP-activated protein kinase phosphorylation and expression of macrophage inflammatory protein 2 (an interleukin-8 homolog) in lung epithelial cells and lungs and lung inflammation, all of which were reduced by Compound C treatment.

CONCLUSIONS

Interleukin-8 induction by wood smoke extract in lung epithelial cells is mediated by novel NADPH oxidase-dependent, reactive oxygen species-sensitive AMP-activated protein kinase signaling with Jun N-terminal kinase and extracellular signal-regulated kinase as the downstream kinases and nuclear factor-κB and signal transducer and activator of transcription protein 3 as the downstream transcription factors. This AMP-activated protein kinase signaling is likely important for inducing lung inflammation with toxic smoke exposure in mice.

Administration of poly(ADP-ribose) polymerase inhibitor into bronchial artery attenuates pulmonary pathophysiology after smoke inhalation and burn in an ovine model

Poly(ADP-ribose) polymerase (PARP) is well known to be an enzyme that repairs damaged DNA and also induces cell death when overactivated. It has been reported that PARP plays a significant role in burn and smoke inhalation injury, and the pathophysiology is thought to be localized in the airway during early stages of activation. Therefore, we hypothesized that local inhibition of PARP in the airway by direct delivery of low dose PJ-34 [poly(ADP-ribose) polymerase inhibitor] into the bronchial artery would attenuate burn and smoke-induced acute lung injury. The bronchial artery in sheep was cannulated in preparation for surgery. After a 5-7 day recovery period, sheep were administered a burn and inhalation injury. Adult female sheep (n=19) were divided into four groups following the injury: (1) PJ-34 group A: 1h post-injury, PJ-34 (0.003mg/kg/h, 2mL/h) was continuously injected into the bronchial artery, n=5; (2) PJ-34 group B: 1h post-injury, PJ-34 (0.03mg/kg/h, 2mL/h) was continuously injected into bronchial artery, n=4; (3) CONTROL GROUP: 1h post-injury, an equivalent amount of saline was injected into the bronchial artery, n=5; (4) Sham group: no injury, no treatment, same operation and anesthesia, n=5. After injury, all animals were placed on a ventilator and fluid resuscitated equally. Pulmonary function as evaluated by measurement of blood gas analysis, pulmonary mechanics, and pulmonary transvascular fluid flux was severely deteriorated in the control group. However, the above changes were markedly attenuated by PJ-34 infusion into the bronchial artery (P/F ratio at 24h: PJ-34 group A 398±40*, PJ-34 group B 438±41*†‡, Control 365±58*, Sham 547±47; * vs. sham [p<0.05], † vs. control [p<0.05], ‡ vs. PJ-34 group A [p<0.05]). Our data strongly suggest that local airway production of poly(ADP-ribose) polymerase contributes to pulmonary dysfunction following smoke inhalation and burn.

Direct delivery of low-dose 7-nitroindazole into the bronchial artery attenuates pulmonary pathophysiology after smoke inhalation and burn injury in an ovine model

Bronchial circulation plays a critical role in the pathophysiology of burn and smoke inhalation-induced acute lung injury. A 10-fold increase in bronchial blood flow is associated with excessive production of nitric oxide (NO) following smoke inhalation and cutaneous burn. Because an increased release of neuropeptides from the airway has been implicated in smoke inhalation injury, we hypothesized that direct delivery into the bronchial artery of low-dose 7-nitroindazole (7-NI), a specific neuronal NO synthase inhibitor, would attenuate smoke/burn-induced acute lung injury. Eighteen adult female sheep were instrumented for chronic hemodynamic monitoring 5 to 7 days before the injury. The bronchial artery was cannulated via intercostal thoracotomy, while blood flow was preserved. Acute lung injury was induced by 40% total body surface area third-degree cutaneous burn and smoke inhalation (48 breaths of cotton smoke, <40°C) under deep anesthesia. Following injury, animals (35.4 ± 1.1 kg) were divided into three groups: (a) 7-NI group: 1 h after injury, 7-NI (0.01 mg · kg · h, 2 mL · h) was continuously infused into the bronchial artery, n = 6; (b) control group: 1 h after injury, same amount of saline was injected into the bronchial artery, n = 6; (c) sham group: no injury, no treatment, same operation and anesthesia, n = 6. After injury, all animals were ventilated and fluid resuscitated according to an established protocol. The experiment was conducted for 24 h. Injury induced severe pulmonary dysfunction, which was associated with increases in lung edema formation, airway obstruction, malondialdehyde, and nitrate/nitrite. 7-Nitroindazole injection into the bronchial artery reduced the degree of lung edema formation and improved pulmonary gas exchange. The increase in malondialdehyde and nitrate/nitrite in lung tissue was attenuated by treatment. Our data strongly suggest that local airway production of NO contributes to pulmonary dysfunction following smoke inhalation and burn injury. Most mechanisms that drive this pathophysiology reside in the airway.

Beneficial effects of concomitant neuronal and inducible nitric oxide synthase inhibition in ovine burn and inhalation injury

Different isoforms of nitric oxide (NO) synthase are critically involved in the development of pulmonary failure secondary to acute lung injury. Here we tested the hypothesis that simultaneous blockade of inducible and neuronal NO synthase effectively prevents the pulmonary lesions in an ovine model of acute respiratory distress syndrome induced by combined burn and smoke inhalation injury. Chronically instrumented sheep were allocated to a sham-injured group (n = 6), an injured and untreated group (n = 6), or an injured group treated with simultaneous infusion of selective inducible and neuronal NO synthase inhibitors (n = 5). The injury was induced by 48 breaths of cotton smoke and a third-degree burn of 40% total body surface area. All sheep were mechanically ventilated and fluid resuscitated. The injury induced severe pulmonary dysfunction as indicated by decreases in PaO2/FiO2 ratio and increases in pulmonary shunt fraction, ventilatory pressures, lung lymph flow, and lung wet/dry weight ratio. The treatment fully prevented the elevations in lymph and plasma nitrate/nitrite levels, pulmonary shunting, ventilatory pressures, lung lymph flow, and wet/dry weight ratio and significantly attenuated the decline in PaO2/FiO2 ratio. In conclusion, simultaneous blockade of inducible and neuronal NO synthase exerts beneficial pulmonary effects in an ovine model of acute respiratory distress syndrome secondary to combined burn and smoke inhalation injury. This novel treatment strategy may represent a useful therapeutic adjunct for patients with these injuries.

Preclinical evaluation of epinephrine nebulization to reduce airway hyperemia and improve oxygenation after smoke inhalation injury

OBJECTIVE

Acute lung injury secondary to smoke inhalation is a major source of morbidity and mortality in burn patients. We tested the hypothesis that nebulized epinephrine would ameliorate pulmonary dysfunction secondary to acute lung injury by reducing airway hyperemia and edema formation and mediating bronchodilatation in an established, large animal model of inhalation injury.

DESIGN

Prospective, controlled, randomized trial.

SETTING

University research laboratory.

SUBJECTS

Twenty-four chronically instrumented, adult, female sheep.

INTERVENTIONS

Following baseline measurements, the animals were allocated to a sham-injured group (n = 5), an injured and saline-treated group (n = 6), or an injured group treated with 4 mg of nebulized epinephrine every 4 hrs (n = 6). Inhalation injury was induced by 48 breaths of cotton smoke. The dose of epinephrine was derived from dose finding experiments (n = 7 sheep).

MEASUREMENTS AND MAIN RESULTS

The injury induced significant increases in airway blood flows, bronchial wet/dry weight ratio, airway obstruction scores, ventilatory pressures, and lung malondialdehyde content, and contributed to severe pulmonary dysfunction as evidenced by a significant decline in Pao₂/Fio₂ ratio and increase in pulmonary shunt fraction. Nebulization of epinephrine significantly reduced tracheal and main bronchial blood flows, ventilatory pressures, and lung malondialdehyde content. The treatment was further associated with significant improvements of Pao₂/FIO₂ ratio and pulmonary shunting.

CONCLUSIONS

Nebulization of epinephrine reduces airway blood flow and attenuates pulmonary dysfunction in sheep subjected to severe smoke inhalation injury. Future studies will have to improve the understanding of the underlying pathomechanisms and identify the optimal dosing for the treatment of patients with this injury.

Review of burn injury research for the year 2009

Research in burn care for the calendar year 2009 was robust and diverse with >1400 research articles published on a wide range of topics. In this review, the authors highlight some innovative and potentially impactful research related to the overall care of burn- injured patients. The authors grouped articles according to the following categories: critical care, infection, inhalation injury, epidemiology, psychology, wound characterization and treatment, nutrition and metabolism, pain and itch management, burn reconstruction, and rehabilitation. They found that the holistic nature of burn care is reflected in the diverse research performed in 2009 throughout the world and that this research has provided important evidence that has improved or will improve burn care overall.

Beneficial pulmonary effects of a metalloporphyrinic peroxynitrite decomposition catalyst in burn and smoke inhalation injury

During acute lung injury, nitric oxide (NO) exerts cytotoxic effects by reacting with superoxide radicals, yielding the reactive nitrogen species peroxynitrite (ONOO(-)). ONOO(-) exerts cytotoxic effects, among others, by nitrating/nitrosating proteins and lipids, by activating the nuclear repair enzyme poly(ADP-ribose) polymerase and inducing VEGF. Here we tested the effect of the ONOO(-) decomposition catalyst INO-4885 on the development of lung injury in chronically instrumented sheep with combined burn and smoke inhalation injury. The animals were randomized to a sham-injured group (n = 7), an injured control group [48 breaths of cotton smoke, 3rd-degree burn of 40% total body surface area (n = 7)], or an injured group treated with INO-4885 (n = 6). All sheep were mechanically ventilated and fluid-resuscitated according to the Parkland formula. The injury-related increases in the abundance of 3-nitrotyrosine, a marker of protein nitration by ONOO(-), were prevented by INO-4885, providing evidence for the neutralization of ONOO(-) action by the compound. Burn and smoke injury induced a significant drop in arterial Po(2)-to-inspired O(2) fraction ratio and significant increases in pulmonary shunt fraction, lung lymph flow, lung wet-to-dry weight ratio, and ventilatory pressures; all these changes were significantly attenuated by INO-4885 treatment. In addition, the increases in IL-8, VEGF, and poly(ADP-ribose) in lung tissue were significantly attenuated by the ONOO(-) decomposition catalyst. In conclusion, the current study suggests that ONOO(-) plays a crucial role in the pathogenesis of pulmonary microvascular hyperpermeability and pulmonary dysfunction following burn and smoke inhalation injury in sheep. Administration of an ONOO(-) decomposition catalyst may represent a potential treatment option for this injury.

Molecular biological effects of selective neuronal nitric oxide synthase inhibition in ovine lung injury

Neuronal nitric oxide synthase is critically involved in the pathogenesis of acute lung injury resulting from combined burn and smoke inhalation injury. We hypothesized that 7-nitroindazole, a selective neuronal nitric oxide synthase inhibitor, blocks central molecular mechanisms involved in the pathophysiology of this double-hit insult. Twenty-five adult ewes were surgically prepared and randomly allocated to 1) an uninjured, untreated sham group (n = 7), 2) an injured control group with no treatment (n = 7), 3) an injury group treated with 7-nitroindazole from 1-h postinjury to the remainder of the 24-h study period (n = 7), or 4) a sham-operated group subjected only to 7-nitroindazole to judge the effects in health. The combination injury was associated with twofold increased activity of neuronal nitric oxide synthase and oxidative/nitrosative stress, as indicated by significant increases in plasma nitrate/nitrite concentrations, 3-nitrotyrosine (an indicator of peroxynitrite formation), and malondialdehyde lung tissue content. The presence of systemic inflammation was evidenced by twofold, sixfold, and threefold increases in poly(ADP-ribose) polymerase, IL-8, and myeloperoxidase lung tissue concentrations, respectively (each P < 0.05 vs. sham). These molecular changes were linked to tissue damage, airway obstruction, and pulmonary shunting with deteriorated gas exchange. 7-Nitroindazole blocked, or at least attenuated, all these pathological changes. Our findings suggest 1) that nitric oxide formation derived from increased neuronal nitric oxide synthase activity represents a pivotal reactive agent in the patho-physiology of combined burn and smoke inhalation injury and 2) that selective neuronal nitric oxide synthase inhibition represents a goal-directed approach to attenuate the degree of injury.