Mechanisms of acute lung injury/acute respiratory distress syndrome

Vitamin C: Rationale for Its Use in Sepsis-Induced Acute Respiratory Distress Syndrome (ARDS)

Acute respiratory distress syndrome (ARDS) is a life-threatening event that occurs in patients suffering from bacterial, fungal, or viral sepsis. Research performed over the last five decades showed that ARDS is a consequence of severe unrestrained systemic inflammation, which leads to injury of the lung's microvasculature and alveolar epithelium. ARDS leads to acute hypoxic/hypercapnic respiratory failure and death in a significant number of patients hospitalized in intensive care units worldwide. Basic and clinical research performed during the time since ARDS was first described has been unable to construct a pharmacological agent that will combat the inflammatory fire leading to ARDS. In-depth studies of the molecular pharmacology of vitamin C indicate that it can serve as a potent anti-inflammatory agent capable of attenuating the pathobiological events that lead to acute injury of the lungs and other body organs. This analysis of vitamin C's role in the treatment of ARDS includes a focused systematic review of the literature relevant to the molecular physiology of vitamin C and to the past performance of clinical trials using the agent.

Arabincoside B isolated from Caralluma arabica as a potential anti-pneumonitis in LPS mice model

Acute lung injury (ALI) is a life-threatening condition usually associated with poor therapeutic outcomes and a high mortality rate. Since 2019, the situation has worsened due to the COVID-19 pandemic. ALI had approximately 40% of deaths before COVID-19, mainly due to the dysfunction of the blood-gas barrier that led to lung edema, failure of gas exchange, and dyspnea. Many strategies have been taken to mitigate the disease condition, such as diuretics, surfactants, antioxidants, glucocorticoids, heparin, and ventilators with concomitant sedatives. However, until now, there is no available effective therapy for ALI. Thus, we are presenting a new compound termed Arabincoside B (AR-B), recently isolated from Caralluma arabica, to be tested in such conditions. For that, the lipopolysaccharide (LPS) mice model was used to investigate the capability of the AR-B compound to control the ALI compared to standard dexamethasone. The results showed that AR-B had a significant effect on retrieving ALI. A further mechanistic study carried out in the serum, lung homogenate, histological, and immunohistochemistry sections revealed that the AR-B either in 50 mg/kg or 75 mg/kg dose inhibited pro-inflammatory cytokines such as IL-6, IL-13, NF-κB, TNFα, and NO and stimulated regulatory cytokines IL-10. Moreover, AR-B showed a considerable potential to protect the pulmonary tissue against oxidative stress by decreasing MDA and increasing catalase and Nrf2. Also, the AR-B exhibited an anti-apoptotic effect on the lung epithelium, confirmed by reducing COX and BAX expression and upregulating Bcl-2 expression. These results pave its clinical application for ALI.

Sex Hormones and Lung Inflammation

Inflammation is a characteristic marker in numerous lung disorders. Several immune cells, such as macrophages, dendritic cells, eosinophils, as well as T and B lymphocytes, synthetize and release cytokines involved in the inflammatory process. Gender differences in the incidence and severity of inflammatory lung ailments including asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis (PF), lung cancer (LC), and infectious related illnesses have been reported. Moreover, the effects of sex hormones on both androgens and estrogens, such as testosterone (TES) and 17β-estradiol (E2), driving characteristic inflammatory patterns in those lung inflammatory diseases have been investigated. In general, androgens seem to display anti-inflammatory actions, whereas estrogens produce pro-inflammatory effects. For instance, androgens regulate negatively inflammation in asthma by targeting type 2 innate lymphoid cells (ILC2s) and T-helper (Th)-2 cells to attenuate interleukin (IL)-17A-mediated responses and leukotriene (LT) biosynthesis pathway. Estrogens may promote neutrophilic inflammation in subjects with asthma and COPD. Moreover, the activation of estrogen receptors might induce tumorigenesis. In this chapter, we summarize the most recent advances in the functional roles and associated signaling pathways of inflammatory cellular responses in asthma, COPD, PF, LC, and newly occurring COVID-19 disease. We also meticulously deliberate the influence of sex steroids on the development and progress of these common and severe lung diseases.

Loss of Nucleobindin-2/Nesfatin-1 increases lipopolysaccharide-induced murine acute lung inflammation

NUCB2/nesfatin-1 is expressed in variety of tissues. Treatment with nesfatin-1 reduces inflammation in rat models of subarachnoid hemorrhage-induced oxidative brain damage and traumatic brain injury as well as myocardial injury. There is only one study showing anti-inflammatory actions of nesfatin-1 on acute lung inflammation. To more precisely determine the role of NUCB2/nesfatin-1 in acute lung inflammation, we conducted a study using NUCB2/nesfatin-1 knockout (NKO) mice as well as neutrophils isolated from the bone marrows of WT and NKO mice. Our findings suggest that the absence of NUCB2/nesfatin-1 significantly increases the accumulation of adherent neutrophils by approximately 3 times compared with WT within LPS-treated lungs. Integrating this with observations from both BALF and neutrophil cytokine expression, we propose that although neutrophils lacking NUCB2/nesfatin-1 individually secrete less pro-inflammatory cytokines compared with stimulated WT cells, the result of knocking out NUCB2/nesfatin-1 is net pro-inflammatory. No change was found in NUCB2/nesfatin-1 mRNA or protein expression comparing WT LPS and PBS-treated samples. Taken together, our results show that NUCB2/nesfatin-1 is constitutively expressed in mouse lungs and neutrophils and demonstrates anti-inflammatory properties in mouse lungs during acute lung injury, by inhibiting adherent neutrophil accumulation and inflammatory cytokine expression.

Supplementation of Adiantum capillus-veneris Modulates Alveolar Apoptosis under Hypoxia Condition in Wistar Rats Exposed to Exercise

Background and Objectives: Several studies have reported that some conditions such as exercise and hypoxia induce DNA damage and dysfunction and apoptosis. Some plant foods contain numerous bioactive compounds and anti-inflammatory properties that can help fight DNA damage. Therefore, the current study evaluated the effect of supplementation of Adiantum capillus-veneris (ACV) extract on Bax/B-cell lymphoma 2 (Bcl-2) ratio apoptotic index and remodeling of pulmonary alveolar epithelial cells in lung tissue of healthy Wistar rats during stressful conditions (hypoxia). Materials and Methods: Twenty-seven Wistar male rats (four-week old, 72 ± 9 g) were randomly assigned into three groups: normoxic, sedentary, and not-supplemented (NG, n = 9); exercise and hypoxia and not-supplemented (HE, n = 9); and exercise and hypoxia and supplemented group (HS, n = 9). The NG remained sedentary in the normoxia environment for nine weeks. The HE group participated in a high-intensity (IT) program for six weeks, then remained sedentary in the hypoxia environment for three weeks. The low-pressure chamber simulated a ~2800 M altitude 24 h/d. HS participated in IT, then entered and remained sedentary in the hypoxia environment for three weeks, and they consumed 500 mg per kg of body weight ACV extract. Results: The Bax/Bcl-2 ratio of the HE group increased significantly (+50.27%, p ≤ 0.05), the average number of type I pneumocytes was reduced significantly (−18.85%, p ≤ 0.05), and the average number of type II pneumocytes was increased significantly (+14.69%, p ≤ 0.05). Also, after three weeks of consuming the ACV extract, the HS group in comparison with the HE group had their Bax/Bcl-2 ratio reduced significantly (−24.27%, p ≤ 0.05), the average number of type I pneumocytes increased significantly (+10.15%, p ≤ 0.05), and the average number of type II pneumocytes reduced significantly (−7.18%, p ≤ 0.05). Conclusion: The findings show that after three weeks of hypoxia following six weeks of high-intensity interval training in Wistar rats, the Bax/Bcl-2 ratio and the number of type II pneumocytes were increased and the number of type I pneumocytes was reduced significantly. These results strongly suggest that an apoptosis state was induced in the lung parenchyma, and consuming ACV extract modulated this state.

Targeting Cytokines as Evolving Treatment Strategies in Chronic Inflammatory Airway Diseases

Cytokines are key players in the initiation and propagation of inflammation in chronic inflammatory airway diseases such as chronic obstructive pulmonary disease (COPD), bronchiectasis and allergic asthma. This makes them attractive targets for specific novel anti-inflammatory treatment strategies. Recently, both interleukin-1 (IL-1) and IL-6 have been associated with negative health outcomes, mortality and a pro-inflammatory phenotype in COPD. IL-6 in COPD was shown to correlate negatively with lung function, and IL-1beta was induced by cigarette smoke in the bronchial epithelium, causing airway inflammation. Furthermore, IL-8 has been shown to be a pro-inflammatory marker in bronchiectasis, COPD and allergic asthma. Clinical trials using specific cytokine blockade therapies are currently emerging and have contributed to reduce exacerbations and steroid use in COPD. Here, we present a review of the current understanding of the roles of cytokines in the pathophysiology of chronic inflammatory airway diseases. Furthermore, outcomes of clinical trials in cytokine blockade as novel treatment strategies for selected patient populations with those diseases will be discussed.

Epidemiology, drug resistance, and pathophysiology of Plasmodium vivax malaria

Malaria, caused by the protozoan parasites of the genus Plasmodium, is a major health problem in many countries of the world. Five parasite species namely, Plasmodium falciparum, P. vivax, P. malariae, P. ovale, and P. knowlesi, cause malaria in humans. Of these, P. falciparum and P. vivax are the most prevalent and account for the majority of the global malaria cases. In most areas of Africa, P. vivax infection is essentially absent because of the inherited lack of Duffy antigen receptor for chemokines on the surface of red blood cells that is involved in the parasite invasion of erythrocytes. Therefore, in Africa, most malaria infections are by P. falciparum and the highest burden of P. vivax infection is in Southeast Asia and South America. Plasmodium falciparum is the most virulent and as such, it is responsible for the majority of malarial mortality, particularly in Africa. Although, P. vivax infection has long been considered to be benign, recent studies have reported life-threatening consequences, including acute respiratory distress syndrome, cerebral malaria, multi-organ failure, dyserythropoiesis and anaemia. Despite exhibiting low parasite biomass in infected people due to parasite's specificity to infect only reticulocytes, P. vivax infection triggers higher inflammatory responses and exacerbated clinical symptoms than P. falciparum, such as fever and chills. Another characteristic feature of P. vivax infection, compared to P. falciparum infection, is persistence of the parasite as dormant liver-stage hypnozoites, causing recurrent episodes of malaria. This review article summarizes the published information on P. vivax epidemiology, drug resistance and pathophysiology.

Protective Effect of Dexmedetomidine on Endotoxin-Induced Acute Lung Injury in Rats

BACKGROUND The purpose of this study was to investigate whether DEX exerts protective mechanisms in rats with acute lung injury (ALI) induced by the endotoxin lipopolysaccharide (LPS). The mortality rate of ALI is extremely high. DEX, an a2 adrenergic receptor agonist, has potent anti-inflammatory and organ-protective effects in addition to its sedative and analgesic properties. We sought to elucidate whether DEX can attenuate acute lung injury. MATERIAL AND METHODS Forty-eight Wister rats were randomly divided into 4 groups (n=12, per group): the normal saline control (NS) group, receiving tail-vein injection of 0.9% normal saline (5 mL/kg); the LPS (L) group, receiving tail-vein injection of LPS (8 mg/kg); the LPS+DEX (L+D) group, receiving tail-vein injection of LPS (8 mg/kg), 0.5h before treated with DEX (50 ug/kg); and the DEX+LPS (D+L) group, receiving tail-vein injection of LPS (8 mg/kg) 0.5 h after being treated with DEX (50 ug/kg). Then, we measured the wet‑to‑dry weight ratio of lung tissue, the ALI pathology score, and HE staining of lung tissue, and assessed the Oxygen Tension index. RESULTS The present study revealed that LPS‑induced rats exhibited significant lung injury, characterized by the deterioration of histopathology, ALI Pathology Score, wet‑to‑dry weight ratio, and Oxygen Tension index (MBP, PaO2, PaCO2, PH, HCO3-, and Lac), which were attenuated by DEX treatment. CONCLUSIONS Collectively, the present results demonstrate elucidate the molecular mechanisms by which DEX ameliorates LPS‑induced ALI.

Plasmodium vivax Biology: Insights Provided by Genomics, Transcriptomics and Proteomics

During the last decade, the vast omics field has revolutionized biological research, especially the genomics, transcriptomics and proteomics branches, as technological tools become available to the field researcher and allow difficult question-driven studies to be addressed. Parasitology has greatly benefited from next generation sequencing (NGS) projects, which have resulted in a broadened comprehension of basic parasite molecular biology, ecology and epidemiology. Malariology is one example where application of this technology has greatly contributed to a better understanding of Plasmodium spp. biology and host-parasite interactions. Among the several parasite species that cause human malaria, the neglected Plasmodium vivax presents great research challenges, as in vitro culturing is not yet feasible and functional assays are heavily limited. Therefore, there are gaps in our P. vivax biology knowledge that affect decisions for control policies aiming to eradicate vivax malaria in the near future. In this review, we provide a snapshot of key discoveries already achieved in P. vivax sequencing projects, focusing on developments, hurdles, and limitations currently faced by the research community, as well as perspectives on future vivax malaria research.

Acute Limb Ischemia-Much More Than Just a Lack of Oxygen

Acute ischemia of an extremity occurs in several stages, a lack of oxygen being the primary contributor of the event. Although underlying patho-mechanisms are similar, it is important to determine whether it is an acute or chronic event. Healthy tissue does not contain enlarged collaterals, which are formed in chronically malperfused tissue and can maintain a minimum supply despite occlusion. The underlying processes for enhanced collateral blood flow are sprouting vessels from pre-existing vessels (via angiogenesis) and a lumen extension of arterioles (via arteriogenesis). While disturbed flow patterns with associated local low shear stress upregulate angiogenesis promoting genes, elevated shear stress may trigger arteriogenesis due to increased blood volume. In case of an acute ischemia, especially during the reperfusion phase, fluid transfer occurs into the tissue while the vascular bed is simultaneously reduced and no longer reacts to vaso-relaxing factors such as nitric oxide. This process results in an exacerbative cycle, in which increased peripheral resistance leads to an additional lack of oxygen. This whole process is accompanied by an inundation of inflammatory cells, which amplify the inflammatory response by cytokine release. However, an extremity is an individual-specific composition of different tissues, so these processes may vary dramatically between patients. The image is more uniform when broken down to the single cell stage. Because each cell is dependent on energy produced from aerobic respiration, an event of acute hypoxia can be a life-threatening situation. Aerobic processes responsible for yielding adenosine triphosphate (ATP), such as the electron transport chain and oxidative phosphorylation in the mitochondria, suffer first, thus disrupting the integrity of cellular respiration. One consequence of this is irreparable damage of the cell membrane due to an imbalance of electrolytes. The eventual increase in net fluid influx associated with a decrease in intracellular pH is considered an end-stage event. Due to the lack of ATP, individual cell organelles can no longer sustain their activity, thus initiating the cascade pathways of apoptosis via the release of cytokines such as the BCL2 associated X protein (BAX). As ischemia may lead to direct necrosis, inflammatory processes are further aggravated. In the case of reperfusion, the flow of nascent oxygen will cause additional damage to the cell, further initiating apoptosis in additional surrounding cells. In particular, free oxygen radicals are formed, causing severe damage to cell membranes and desoxyribonucleic acid (DNA). However, the increased tissue stress caused by this process may be transient, as radical scavengers may attenuate the damage. Taking the above into final consideration, it is clearly elucidated that acute ischemia and subsequent reperfusion is a process that leads to acute tissue damage combined with end-organ loss of function, a condition that is difficult to counteract.

In vitro and in vivo inhibitory effects of 6-hydroxyrubiadin on lipopolysaccharide-induced inflammation

Inflammation is a defensive response against a multitude of harmful stimuli and stress conditions such as tissue injury, and is one of the most common pathological processes of human diseases. 6-Hydroxyrubiadin, an anthraquinone isolated from Rubia cordifolia L., exhibits several bioactive properties. The aim of this study was to evaluate whether 6-hydroxyrubiadin can reduce the production of pro-inflammatory cytokines and ameliorate acute lung injury (ALI) in a mouse model. In this study, we demonstrated that 6-hydroxyrubiadin suppressed lipopolysaccharide (LPS)-induced nuclear factor-kappa B activation as well as the phosphorylation of c-Jun N-terminal kinase in RAW 264.7 macrophages. In addition, we also showed that 6-hydroxyrubiadin inhibited the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 in phorbol myristate acetate (PMA)-primed U937 and RAW 264.7 cells. Furthermore, 6-hydroxyrubiadin treatment reduced the production of these cytokines in vivo and attenuated the severity of LPS-induced ALI. Thus, these results suggested that 6-hydroxyrubiadin may be a potential therapeutic candidate for the treatment of inflammation and inflammatory diseases.

Lung Inflammation Associated With Clinical Acute Necrotizing Pancreatitis in Dogs

Although dogs with acute necrotizing pancreatitis (ANP) can develop respiratory complications, there are no data describing lung injury in clinical cases of ANP in dogs. Therefore, we conducted a study to characterize lung injury and determine if pulmonary intravascular macrophages (PIMs) are induced in dogs with ANP ( n = 21) compared with control dogs ( n = 6). Two pathologists independently graded histologic sections of pancreas from clinical cases to characterize the severity of ANP (total scores of 3–10) compared with controls showing histologically normal pancreas (total scores of 0). Based on histological grading, lungs from dogs with ANP showed inflammation (median score, 1.5; range, 0–3), but the scores did not differ statistically from the control lungs (median score, 0.5; range, 0–2). A grid intersects-counting method showed an increase in the numbers of MAC387-positive alveolar septal mononuclear phagocyte profiles in lungs of dogs with ANP (ratio median, 0.0243; range, 0.0093–0.0734, with 2 outliers at 0.1523 and 0.1978) compared with controls (ratio median, 0.0019; range, 0.0017–0.0031; P < .0001). Only dogs with ANP showed labeling for von Willebrand factor in alveolar septal capillary endothelial cells, septal inflammatory cells, and alveolar macrophages. Toll-like receptor 4 and interleukin 6 were variably expressed in alveolar macrophages and septal inflammatory cells in lungs from both ANP and control dogs. Inducible nitric oxide synthase was detected in alveolar macrophages of dogs with ANP only. These data show that dogs with ANP have lung inflammation, including the recruitment of PIMs and expression of inflammatory mediators.

Regulatory effect of cytokine-induced neutrophil chemoattractant, epithelial neutrophil-activating peptide 78 and pyrrolidine dithiocarbamate on pulmonary neutrophil aggregation mediated by nuclear factor-κB in lipopolysaccharide-induced acute respiratory distress syndrome mice

In the present study, the regulatory effect of cytokine-induced neutrophil chemoattractant (CINC) and epithelial neutrophil-activating peptide 78 (ENA-78) on pulmonary neutrophil (PMN) accumulation in lipopolysaccharide (LPS)-induced acute respiratory distress syndrome (ARDS) mice, and the therapeutic effect of pyrrolidine dithiocarbamate (PDTC), was investigated. BALB/c mice were divided into control, LPS and PDTC + LPS groups using a random number table. The phosphorylation of nuclear factor-κB (NF-κB) was detected using a western blot, and the mRNA expression levels of CINC were evaluated using reverse transcription-quantitative polymerase chain reaction. The expression of NF-κB, CINC and ENA-78 was detected using immunohistochemistry. The production of interleukin (IL)-8 and IL-10 in serum and broncho-alveolar lavage fluid (BALF) was analyzed using an enzyme-linked immunosorbent assay. The total number of leukocytes and proportion of PMNs in BALF was also determined. Following injection with LPS (20 mg/kg), the expression levels of p-NF-κB, CINC and ENA-78 were increased in lung tissue, and the expression levels of IL-8, IL-10 and the number of PMNs increased in serum and BALF. However, in comparison with the LPS group, the degree of lung injury was reduced in ARDS mice that were treated with PDTC. In addition, the expression level of p-NF-κB and the production of chemokines in lung tissue decreased in ARDS mice that were treated with PDTC, and the number of PMNs in BALF also decreased. In conclusion, the results of the present study suggest that the LPS-induced phosphorylation of NF-κB may result in the synthesis and release of CINC and ENA-78, which induce the accumulation of PMNs in the lung. Therefore, PDTC may be used to reduce the production of chemokines and cytokines, thereby decreasing the activation of PMNs in lung tissue and reducing the damage of lung tissue in ARDS.

Hesperetin attenuates ventilator-induced acute lung injury through inhibition of NF-κB-mediated inflammation

Hesperetin, a major bioflavonoid in sweet oranges and lemons, has been reported to have anti-inflammatory properties. However, the effect of hesperetin on ventilator-induced acute lung injury has not been studied. In present study, we investigated the protective effect of hesperetin on ventilator-induced acute lung injury in rats. Rats were orally administered hesperetin (10, 20, or 40mg/kg) two hour before acute lung injury was induced by mechanical ventilation. Rats were then randomly divided into six groups: the lung protective ventilation group (n=20, LV group), injurious ventilation group (n=20, HV group), vehicle-treated injurious ventilation group (n=20, LV+vehicle group), hesperetin (10mg/kg)-treated acute lung injury group (n=20, HV+Hsp (10mg)), hesperetin (20mg/kg)-treated acute lung injury group (n=20, HV+Hsp (20mg)), and hesperetin (40mg/kg)-treated acute lung injury group (n=20, HV+Hsp (40mg)). The lung tissues and bronchoalveolar lavage fluid were isolated for subsequent measurements. Treatment with hesperetin dramatically improved the histology of lung tissue, and reduced the wet/dry ratio, myeloperoxidase activity, protein concentration, and production of tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-1β, and MIP-2 in the bronchoalveolar lavage fluid of rats with ventilator-induced acute lung injury. Additionally, our study indicated that this protective effect of hesperetin results from its ability to increase the expression of peroxisome proliferator-activated receptor (PPAR)-γ and inhibit the activation of the nuclear factor (NF)-κB pathway. These results suggest that hesperetin may be a potential novel therapeutic candidate for protection against ventilator-induced acute lung injury.

Proteomic profiles in acute respiratory distress syndrome differentiates survivors from non-survivors

Acute Respiratory Distress Syndrome (ARDS) continues to have a high mortality. Currently, there are no biomarkers that provide reliable prognostic information to guide clinical management or stratify risk among clinical trial participants. The objective of this study was to probe the bronchoalveolar lavage fluid (BALF) proteome to identify proteins that differentiate survivors from non-survivors of ARDS. Patients were divided into early-phase (1 to 7 days) and late-phase (8 to 35 days) groups based on time after initiation of mechanical ventilation for ARDS (Day 1). Isobaric tags for absolute and relative quantitation (iTRAQ) with LC MS/MS was performed on pooled BALF enriched for medium and low abundance proteins from early-phase survivors (n = 7), early-phase non-survivors (n = 8), and late-phase survivors (n = 7). Of the 724 proteins identified at a global false discovery rate of 1%, quantitative information was available for 499. In early-phase ARDS, proteins more abundant in survivors mapped to ontologies indicating a coordinated compensatory response to injury and stress. These included coagulation and fibrinolysis; immune system activation; and cation and iron homeostasis. Proteins more abundant in early-phase non-survivors participate in carbohydrate catabolism and collagen synthesis, with no activation of compensatory responses. The compensatory immune activation and ion homeostatic response seen in early-phase survivors transitioned to cell migration and actin filament based processes in late-phase survivors, revealing dynamic changes in the BALF proteome as the lung heals. Early phase proteins differentiating survivors from non-survivors are candidate biomarkers for predicting survival in ARDS.

Obesity and nutrition in acute respiratory distress syndrome

This article discusses obesity, its contribution to clinical outcomes, and the current literature on nutrition. More than one third of Americans are obese. Literature suggests that, among critically ill patients, the relationship between obesity and outcomes is complex. Obese patients may be at greater risk of developing acute respiratory distress syndrome (ARDS) than normal weight patients. Although obesity may confer greater morbidity in intensive care, it seems to decrease mortality. ARDS is a catabolic state; patients demonstrate a profound inflammatory response, multiple organ dysfunction, and hypermetabolism, often with malnutrition. The concept of pharmaconutrition has emerged.

The role of leptin in the development of pulmonary neutrophilia in infection and acute lung injury

OBJECTIVES

One of the hallmarks of severe pneumonia and associated acute lung injury is neutrophil recruitment to the lung. Leptin is thought to be up-regulated in the lung following injury and to exert diverse effects on leukocytes, influencing both chemotaxis and survival. We hypothesized that pulmonary leptin contributes directly to the development of pulmonary neutrophilia during pneumonia and acute lung injury.

DESIGN

Controlled human and murine in vivo and ex vivo experimental studies.

SETTING

Research laboratory of a university hospital.

SUBJECTS

Healthy human volunteers and subjects hospitalized with bacterial and H1N1 pneumonia. C57Bl/6 and db/db mice were also used.

INTERVENTIONS

Lung samples from patients and mice with either bacterial or H1N1 pneumonia and associated acute lung injury were immunostained for leptin. Human bronchoalveolar lavage samples obtained after lipopolysaccharide-induced lung injury were assayed for leptin. C57Bl/6 mice were examined after oropharyngeal aspiration of recombinant leptin alone or in combination with Escherichia coli- or Klebsiella pneumoniae-induced pneumonia. Leptin-resistant (db/db) mice were also examined using the E. coli model. Bronchoalveolar lavage neutrophilia and cytokine levels were measured. Leptin-induced chemotaxis was examined in human blood- and murine marrow-derived neutrophils in vitro.

MEASUREMENTS AND MAIN RESULTS

Injured human and murine lung tissue showed leptin induction compared to normal lung, as did human bronchoalveolar lavage following lipopolysaccharide instillation. Bronchoalveolar lavage neutrophilia in uninjured and infected mice was increased and lung bacterial load decreased by airway leptin administration, whereas bronchoalveolar lavage neutrophilia in infected leptin-resistant mice was decreased. In sterile lung injury by lipopolysaccharide, leptin also appeared to decrease airspace neutrophil apoptosis. Both human and murine neutrophils migrated toward leptin in vitro, and this required intact signaling through the Janus Kinase 2/phosphatidylinositol-4,5-bisphosphate 3-kinase pathway.

CONCLUSIONS

We demonstrate that pulmonary leptin is induced in injured human and murine lungs and that this cytokine is effective in driving alveolar airspace neutrophilia. This action appears to be caused by direct effects of leptin on neutrophils.

Paraquat poisoning induces TNF-α-dependent iNOS/NO mediated hyporesponsiveness of the aorta to vasoconstrictors in rats

Paraquat is a toxic herbicide that may induce acute lung injury, circulatory failure and death. The present work aimed at investigating whether there is systemic inflammation and vascular dysfunction after paraquat exposure and whether these parameters were related. There was neutrophilia and accumulation of neutrophils in lung and bronchoalveolar lavage of animals given paraquat. This was associated with an increase in serum levels of TNF-α. In rats given paraquat, the relaxant response of aortic rings to acetylcholine was not modified but the contractile response to phenylephrine was greatly reduced. Endothelium removal or treatment with non-selective (L-NAME) or selective (L-NIL) inhibitors of inducible nitric oxide synthase (iNOS) restored contraction of aortas. There was greater production of nitric oxide (NO), which was restored to basal level by L-NIL, and greater expression of iNOS in endothelial cells, as seen by Western blot analyses and confocal microscopy. Blockade of TNF-α reduced pulmonary and systemic inflammation and vascular dysfunction. Together, our results clearly show that paraquat causes pulmonary and systemic inflammation, and vascular dysfunction in rats. Vascular dysfunction is TNF-α dependent, associated with enhanced expression of iNOS in aortic endothelial cells and greater NO production, which accounts for the decreased responsiveness of aortas to vasoconstrictors. Blockers of TNF-α may be useful in patients with paraquat poisoning.

Plasmodium vivax: clinical spectrum, risk factors and pathogenesis

Vivax malaria was historically described as 'benign tertian malaria' because individual clinical episodes were less likely to cause severe illness than Plasmodium falciparum. Despite this, Plasmodium vivax was, and remains, responsible for major morbidity and significant mortality in vivax-endemic areas. Single infections causing febrile illness in otherwise healthy individuals rarely progress to severe disease. Nevertheless, in the presence of co-morbidities, P. vivax can cause severe illness and fatal outcomes. Recurrent or chronic infections in endemic areas can cause severe anaemia and malnutrition, particularly in early childhood. Other severe manifestations include acute lung injury, acute kidney injury and uncommonly, coma. Multiorgan failure and shock are described but further studies are needed to investigate the role of bacterial and other co-infections in these syndromes. In pregnancy, P. vivax infection can cause maternal anaemia, miscarriage, low birth weight and congenital malaria. Compared to P. falciparum, P. vivax has a greater capacity to elicit an inflammatory response, resulting in a lower pyrogenic threshold. Conversely, cytoadherence of P. vivax to endothelial cells is less frequent and parasite sequestration is not thought to be a significant cause of severe illness in vivax malaria. With a predilection for young red cells, P. vivax does not result in the high parasite biomass associated with severe disease in P. falciparum, but a four to fivefold greater removal of uninfected red cells from the circulation relative to P. falciparum is associated with a similar risk of severe anaemia. Mechanisms underlying the pathogenesis of severe vivax syndromes remain incompletely understood.

Statins as a novel therapeutic strategy in acute lung injury

Acute lung injury (ALI) is a devastating clinical condition associated with pulmonary and systemic inflammation and characterized by incompetence of the pulmonary microvascular barrier culminating in noncardiogenic pulmonary edema. An understanding of the mechanisms underlying endothelial barrier dysfunction in ALI has been facilitated by study of the effects of statins in relevant cellular and animals models. Many of the pleotropic properties of these drugs, including direct effects on endothelial cell (EC) cytoskeletal rearrangement, NADPH oxidase, and nitric oxide activity, as well as effects on differential EC gene expression, are relevant to the pathobiology of ALI and suggest a potential therapeutic role for statins in this context. Moreover, results from preclinical studies and observations in relevant patient populations support the protective potential of statins in ALI, paving the way now for definitive clinical trials.

Biomarkers in acute lung injury

Acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) result in high permeability pulmonary edema causing hypoxic respiratory failure with high morbidity and mortality. As the population ages, the incidence of ALI is expected to rise. Over the last decade, several studies have identified biomarkers in plasma and bronchoalveolar lavage fluid providing important insights into the mechanisms involved in the pathophysiology of ALI. Several biomarkers have been validated in subjects from the large, multicenter ARDS clinical trials network. Despite these studies, no single or group of biomarkers has made it into routine clinical practice. New high throughput "omics" techniques promise improved understanding of the biologic processes in the pathogenesis in ALI and possibly new biomarkers that predict disease and outcomes. In this article, we review the current knowledge on biomarkers in ALI.

Obesity is associated with neutrophil dysfunction and attenuation of murine acute lung injury

Although obesity is implicated in numerous health complications leading to increased mortality, the relationship between obesity and outcomes for critically ill patients appears paradoxical. Recent studies have reported better outcomes and lower levels of inflammatory cytokines in obese patients with acute lung injury (ALI)/acute respiratory distress syndrome, suggesting that obesity may ameliorate the effects of this disease. We investigated the effects of obesity in leptin-resistant db/db obese and diet-induced obese mice using an inhaled LPS model of ALI. Obesity-associated effects on neutrophil chemoattractant response were examined in bone marrow neutrophils using chemotaxis and adoptive transfer; neutrophil surface levels of chemokine receptor CXCR2 were determined by flow cytometry. Airspace neutrophilia, capillary leak, and plasma IL-6 were all decreased in obese relative to lean mice in established lung injury (24 h). No difference in airspace inflammatory cytokine levels was found between obese and lean mice in both obesity models during the early phase of neutrophil recruitment (2-6 h), but early airspace neutrophilia was reduced in db/db obese mice. Neutrophils from uninjured obese mice demonstrated diminished chemotaxis to the chemokine keratinocyte cytokine compared with lean control mice, and adoptive transfer of obese mouse neutrophils into injured lean mice revealed a defect in airspace migration of these cells. Possibly contributing to this defect, neutrophil CXCR2 expression was significantly lower in obese db/db mice, and a similar but nonsignificant decrease was seen in diet-induced obese mice. ALI is attenuated in obese mice, and this blunted response is in part attributable to an obesity-associated abnormal neutrophil chemoattractant response.

Lung and brainstem cytokine levels are associated with breathing pattern changes in a rodent model of acute lung injury

Acute lung injury evokes a pulmonary inflammatory response and changes in the breathing pattern. The inflammatory response has a centrally mediated component which depends on the vagi. We hypothesize that the central inflammatory response, complimentary to the pulmonary inflammatory response, is expressed in the nuclei tractus solitarii (nTS) and that the expression of cytokines in the nTS is associated with breathing pattern changes. Adult, male Sprague-Dawley rats (n=12) received intratracheal instillation of either bleomycin (3units in 120μl of saline) or saline (120μl). Respiratory pattern changed by 24h. At 48h, bronchoalveolar lavage fluid and lung tissue had increased IL-1β and TNF-α levels, but not IL-6. No changes in these cytokines were noted in serum. Immunocytochemical analysis of the brainstem indicated increased expression of IL-1β in the nTS commissural subnucleus that was localized to neurons. We conclude that breathing pattern changes in acute lung injury were associated with increased levels of IL-1β in brainstem areas which integrate cardio-respiratory sensory input.

Immunodetection of occult eosinophils in lung tissue biopsies may help predict survival in acute lung injury

BACKGROUND

Acute lung injury (ALI) is a serious respiratory disorder for which therapy is primarily supportive once infection is excluded. Surgical lung biopsy may rule out other diagnoses, but has not been generally useful for therapy decisions or prognosis in this setting. Importantly, tissue and peripheral blood eosinophilia, the hallmarks of steroid-responsive acute eosinophilic pneumonia, are not commonly linked with ALI. We hypothesized that occult eosinophilic pneumonia may explain better outcomes for some patients with ALI.

METHODS

Immunohistochemistry using a novel monoclonal antibody recognizing eosinophil peroxidase (EPX-mAb) was used to assess intrapulmonary eosinophil accumulation/degranulation. Lung biopsies from ALI patients (n = 20) were identified following review of a pathology database; 45% of which (i.e., 9/20) displayed classical diffuse alveolar damage (ALI-DAD). Controls were obtained from uninvolved tissue in patients undergoing lobectomy for lung cancer (n = 10). Serial biopsy sections were stained with hematoxylin and eosin (H&E) and subjected to EPX-mAb immunohistochemistry.

RESULTS

EPX-mAb immunohistochemistry provided a >40-fold increased sensitivity to detect eosinophils in the lung relative to H&E stained sections. This increased sensitivity led to the identification of higher numbers of eosinophils in ALI patients compared with controls; differences using H&E staining alone were not significant. Clinical assessments showed that lung infiltrating eosinophil numbers were higher in ALI patients that survived hospitalization compared with non-survivors. A similar conclusion was reached quantifying eosinophil degranulation in each biopsy.

CONCLUSION

The enhanced sensitivity of EPX-mAb immunohistochemistry uniquely identified eosinophil accumulation/degranulation in patients with ALI relative to controls. More importantly, this method was a prognostic indicator of patient survival. These observations suggest that EPX-mAb immunohistochemistry may represent a diagnostic biomarker identifying a subset of ALI patients with improved clinical outcomes.

Race/ethnicity and acute respiratory distress syndrome: a National Trauma Data Bank study

BACKGROUND

A study in the general population has shown a higher acute respiratory distress syndrome (ARDS) mortality among blacks. We studied whether black blunt-trauma patients experience different ARDS incidence, ARDS-associated mortality, or ARDS case fatality rates.

METHODS

National Trauma Data Bank (NTDB) extracts of blunt-trauma patients with Injury Severity Score (ISS) greater than 16 and length of stay greater than 3 days were used for this study. ARDS incidence, ARDS-associated mortality, and ARDS case fatality rates were calculated for Caucasians, blacks, and Hispanics, and compared using chi2. In order to adjust for confounders (age, gender, comorbidities, hypotension, and injury severity) multiple logistic regression models were built for the 3 outcomes. Odd ratios (ORs) and 95% confidence intervals (CIs) were calculated. A p < .05 was used for all statistics.

RESULTS

Among the 96350 patients studied, ARDS incidence, ARDS-associated mortality, and ARDS case fatality rates were 0.92%, 0.18%, and 19.1%, respectively. Differences among racial/ethnic groups were found between blacks and Caucasians for ARDS incidence (0.70% vs. 0.93%) and between Hispanic and Caucasians for ARDS-associated mortality (0.27% vs. 0.17%). Multiple logistic regression models adjusting for confounders, using Caucasian race/ethnicity as a reference, revealed a protective effect of black race/ethnicity for ARDS incidence (OR, 0.73; 95% CI, 0.58-0.91). Hispanics, but not blacks, experienced higher odds of adjusted ARDS-associated mortality (OR, 1.76; 95% CI, 1.15-2.62) and ARDS case fatality (OR, 1.92; 95% CI, 1.17-3.09).

CONCLUSIONS

Black race/ethnicity is not associated with ARDS mortality among blunt-trauma patients. Black race/ethnicity seems to have a protective effect in relation to ARDS incidence. Hispanic ethnicity was associated with a higher mortality and case fatality rates for ARDS.

The paradox of the neutrophil's role in tissue injury

The neutrophil is an essential component of the innate immune system, and its function is vital to human life. Its production increases in response to virtually all forms of inflammation, and subsequently, it can accumulate in blood and tissue to varying degrees. Although its participation in the inflammatory response is often salutary by nature of its normal interaction with vascular endothelium and its capability to enter tissues and respond to chemotactic gradients and to phagocytize and kill microrganisms, it can contribute to processes that impair vascular integrity and blood flow. The mechanisms that the neutrophil uses to kill microorganisms also have the potential to injure normal tissue under special circumstances. Its paradoxical role in the pathophysiology of disease is particularly, but not exclusively, notable in seven circumstances: 1) diabetic retinopathy, 2) sickle cell disease, 3) TRALI, 4) ARDS, 5) renal microvasculopathy, 6) stroke, and 7) acute coronary artery syndrome. The activated neutrophil's capability to become adhesive to endothelium, to generate highly ROS, and to secrete proteases gives it the potential to induce local vascular and tissue injury. In this review, we summarize the evidence for its role as a mediator of tissue injury in these seven conditions, making it or its products potential therapeutic targets.

Assessment of lung inflammation with 18F-FDG PET during acute lung injury

OBJECTIVE

The purpose of this review is to describe the current experimental and clinical data regarding the fundamentals and applications of (18)F-FDG PET during acute lung injury (ALI) and acute respiratory distress syndrome (ARDS).

CONCLUSION

Lung inflammation is a key feature of ALI. During ALI, FDG PET can be used to monitor lung neutrophils, which are essential cells in the pathophysiologic mechanisms of ALI. Pulmonary FDG kinetics are altered during experimental and human ALI and are associated with regional lung dysfunction, histologic abnormalities, and prognosis. FDG PET may be a valuable noninvasive method for gaining comprehensive understanding of the mechanisms of ALI/ARDS and for evaluating therapeutic interventions.

The pathologist's approach to acute lung injury

CONTEXT

Acute lung injury and acute respiratory distress syndrome are significant causes of pulmonary morbidity and are frequently fatal. These 2 entities have precise definitions from a clinical standpoint. Histologically, cases from patients with clinical acute lung injury typically exhibit diffuse alveolar damage, but other histologic patterns may occasionally be encountered such as acute fibrinous and organizing pneumonia, acute eosinophilic pneumonia, and diffuse hemorrhage with capillaritis.

OBJECTIVE

To review the diagnostic criteria for various histologic patterns associated with a clinical presentation of acute lung injury and to provide diagnostic aids and discuss the differential diagnosis.

DATA SOURCES

The review is drawn from pertinent peer-reviewed literature and the author's personal experience.

CONCLUSIONS

Acute lung injury remains a significant cause of morbidity and mortality. The pathologist should be aware of histologic patterns of lung disease other than diffuse alveolar damage, which are associated with a clinical presentation of acute lung injury. Identification of these alternative histologic findings, as well as identification of potential etiologic agents, especially infection, may impact patient treatment and disease outcome.

T cell pathways involving CTLA4 contribute to a model of acute lung injury

Acute lung injury (ALI) is a frequent pulmonary complication in critically ill patients. We characterized a murine model of LPS-induced ALI, focusing on Th cells. Following LPS administration, bronchoalveolar lavage lymphocytes, neutrophils, IL-6, TNF-alpha, and albumin were increased. Analysis of LPS-induced T cells revealed increased Th cell-associated cytokines (IL-17A, -17F, and -22), as well as increased expression of CD69 (a cell activation marker), Foxp3, and CTLA4 in CD4(+) T cells. Administration of anti-CTLA4 Ab decreased LPS-induced bronchoalveolar lavage albumin and IL-17A, while increasing CD4(+)Foxp3(+) cell number and Foxp3 expression in CD4(+)Foxp3(+) cells. These data suggest that pulmonary LPS administration promotes CD4(+) T cells and that T cell pathways involving CTLA4 contribute to ALI.

[Acute respiratory failure concomitant with serious disease or injury]

BACKGROUND

Acute respiratory failure has an annual incidence of 20-75/100,000 and is the most common reason for admittance to an intensive care unit. A common cause is acute inflammatory changes in lung tissue. The article reviews clinical, etiological, pathophysiological and therapeutic aspects of acute respiratory failure, with an emphasis on failure secondary to proinflammatory processes.

MATERIAL AND METHODS

This paper is not based on a comprehensive literature review, but on the clinical and scientific experience of the author, literature from a private archive and a limited Medline search.

RESULTS

Acute respiratory failure can be precipitated by agents and/or trauma that damage the lungs directly. Serious infections and tissue damage located in other parts of the body can also cause respiratory failure. In these cases, the blood transports activated blood cells and proinflammatory agents to the lungs where they induce secondary tissue inflammation. The resulting respiratory failure is often serious. Mortality is in the range 30-50 %.

INTERPRETATION

No specific treatment is available for secondary tissue inflammation; it usually resolves when the precipitating injuries or disease processes are healed. Positive pressure ventilation can prevent serious hypoxemia from causing additional damage to affected tissue. With modern treatment in an intensive care unit only 10-15 % of the deaths are caused by the respiratory failure per se, most deaths are caused by failure of several additional organs (multiorgan failure).

Metabolic consequences of acute limb ischemia and their clinical implications

Acute limb ischemia is a common medical condition resulting from arterial embolization, in situ thrombosis, trauma, and other causes. The severity of injury is related to the duration of ischemia and the effects of reperfusion. Metabolic consequences of reperfusion injury can be variable, ranging from transient symptoms in the lower extremity to systemic inflammation with multiple organ dysfunction. This article provides an overview of some of the key mediators of reperfusion injury. Additional discussion is focused on the clinical effects of reperfusion in the extremity, as well as the pulmonary, cardiac, and renal organ systems. A better understanding of these processes may result in improved patient outcomes and decreased mortality.

Diabetes, insulin, and development of acute lung injury

OBJECTIVES

Recently, many studies have investigated the immunomodulatory effects of insulin and glucose control in critical illness. This review examines evidence regarding the relationship between diabetes and the development of acute lung injury/acute respiratory distress syndrome (ALI/ARDS), reviews studies of lung injury related to glycemic and nonglycemic metabolic features of diabetes, and examines the effect of diabetic therapies.

DATA SOURCES AND STUDY SELECTION

A MEDLINE/PubMed search from inception to August 1, 2008, was conducted using the search terms acute lung injury, acute respiratory distress syndrome, hyperglycemia, diabetes mellitus, insulin, hydroxymethylglutaryl-CoA reductase inhibitors (statins), angiotensin-converting enzyme inhibitor, and peroxisome proliferator-activated receptors, including combinations of these terms. Bibliographies of retrieved articles were manually reviewed.

DATA EXTRACTION AND SYNTHESIS

Available studies were critically reviewed, and data were extracted with special attention to the human and animal studies that explored a) diabetes and ALI; b) hyperglycemia and ALI; c) metabolic nonhyperglycemic features of diabetes and ALI; and d) diabetic therapies and ALI.

CONCLUSIONS

Clinical and experimental data indicate that diabetes is protective against the development of ALI/ARDS. The pathways involved are complex and likely include effects of hyperglycemia on the inflammatory response, metabolic abnormalities in diabetes, and the interactions of therapeutic agents given to diabetic patients. Multidisciplinary, multifaceted studies, involving both animal models and clinical and molecular epidemiology techniques, are essential.

The pathophysiology of vivax malaria

Long considered a benign infection, Plasmodium vivax is now recognized as a cause of severe and fatal malaria, despite its low parasite biomass, the increased deformability of vivax-infected red blood cells and an apparent paucity of parasite sequestration. Severe anemia is associated with recurrent bouts of hemolysis of predominantly uninfected erythrocytes with increased fragility, and lung injury is associated with inflammatory increases in alveolar-capillary membrane permeability. Although rare, vivax-associated coma challenges our understanding of pathobiology caused by Plasmodium spp. Host and parasite factors contribute to the risk of severe disease, and comorbidities might contribute to vivax mortality. In this review, we discuss potential mechanisms underlying the syndromes of uncomplicated and severe vivax malaria, identifying key areas for future research.

Inflammatory mechanisms in the lung

Inflammation is the body's response to insults, which include infection, trauma, and hypersensitivity. The inflammatory response is complex and involves a variety of mechanisms to defend against pathogens and repair tissue. In the lung, inflammation is usually caused by pathogens or by exposure to toxins, pollutants, irritants, and allergens. During inflammation, numerous types of inflammatory cells are activated. Each releases cytokines and mediators to modify activities of other inflammatory cells. Orchestration of these cells and molecules leads to progression of inflammation. Clinically, acute inflammation is seen in pneumonia and acute respiratory distress syndrome (ARDS), whereas chronic inflammation is represented by asthma and chronic obstructive pulmonary disease (COPD). Because the lung is a vital organ for gas exchange, excessive inflammation can be life threatening. Because the lung is constantly exposed to harmful pathogens, an immediate and intense defense action (mainly inflammation) is required to eliminate the invaders as early as possible. A delicate balance between inflammation and anti-inflammation is essential for lung homeostasis. A full understanding of the underlying mechanisms is vital in the treatment of patients with lung inflammation. This review focuses on cellular and molecular aspects of lung inflammation during acute and chronic inflammatory states.

Epithelial cell apoptosis and neutrophil recruitment in acute lung injury-a unifying hypothesis? What we have learned from small interfering RNAs

In spite of protective ventilatory strategies, Acute Lung Injury (ALI) remains associated with high morbidity and mortality. One reason for the lack of therapeutic options might be that ALI is a co-morbid event associated with a diverse family of diseases and, thus, may be the result of distinct pathological processes. Among them, activated neutrophil- (PMN-) induced tissue injury and epithelial cell apoptosis mediated lung damage represent two potentially important candidate pathomechanisms that have been put forward. Several approaches have been undertaken to test these hypotheses, with substantial success in the treatment of experimental forms of ALI. With this in mind, we will summarize these two current hypotheses of ALI briefly, emphasizing the role of apoptosis in regulating PMN and/or lung epithelial cell responses. In addition, the contribution that Fas-mediated inflammation may play as a potential biological link between lung cell apoptosis and PMN recruitment will be considered, as well as the in vivo application of small interfering RNA (siRNA) as a novel approach to the inhibition of ALI and its therapeutic implications.