Phospholipase A2-induced lung edema and its mechanism in isolated perfused guinea pig lung

Therapeutic Potential of 2-Methylquinazolin-4(3H)-one as an Antiviral Agent against Influenza A Virus-Induced Acute Lung Injury in Mice

Qingdai-Mabo (QM), a traditional Chinese herbal formula composed of medicinal herb and fungus, has been used for treatment of cough and viral pneumonia. However, the underlying mechanism and bioactive components against anti-influenza A virus remain unclear. In the present study, ethyl acetate (EA) extract of QM decoctions was tested for its biological activity against acute lung injury (ALI) and its main components were identified using UPLC-MS/MS. In total, 18 bioactive components were identified, including 2-Methylquinaozlin-4(3H)-one (C1), which showed significant antiviral activity in vitro with an IC₅₀ of 23.8 μg/mL. Furthermore, we validated the efficacy of C1 in ameliorating ALI lesions and inflammation in influenza A virus-infected mice. The results showed that C1 significantly reduced the lung index, downregulated neuraminidase (NA) and nucleoprotein (NP), and decreased the expression of pro-inflammatory molecules IFN-α, TNF-α, MCP-1, IL-6, and IL-8; however, they enhanced levels of IL-10 and IFN-γ in lung homogenate from mice infected by influenza A virus. In addition, C1 inhibited the recruitment of macrophages. These in vitro and in vivo studies suggested that the significant anti-influenza A virus activity contributed to its curative effect on lesions and inflammation of viral pneumonia in mice. Given its potential antiviral activity against influenza A virus, C1 is determined to be a main active component in the EA extract of QM. Taken together, the antiviral activity of C1 suggests its potential as an effective treatment against viral pneumonia via the inhibition of virus replication, but the mechanism C1 on antiviral research needs to be explored further.

Lethal systemic capillary leak syndrome associated with severe ventilator-induced lung injury: an experimental study

OBJECTIVE

We report the evolution of severe ventilator-induced lung injury associated with lethal systemic capillary leak syndrome, when sheep were ventilated at a peak inspiratory pressure of 50 cm H2O, at a respiratory rate of 8 breaths.min, with an inspiratory time of 2.5 secs.

DESIGN

A prospective laboratory animal study.

SETTING

Experimental animal research laboratory.

SUBJECTS

Mixed breed sheep.

INTERVENTIONS

Sheep were anesthetized, paralyzed, and mechanically ventilated.

MEASUREMENTS AND MAIN RESULTS

This sheep model was characterized by a rapidly evolving massive anasarca, hemoconcentration, cardiac dysfunction, multiple system organ failure, and severe ventilator-induced lung injury. Cardiovascular changes and profound hemoconcentration developed within 6 hrs from the start of mechanical ventilation, along with a major decline in pulmonary compliance and deterioration in arterial blood gases. When total static lung compliance decreased to 0.15 mL (cm H2O)(-1) x kg(-1) (7-30 hrs), the sheep were randomized to two groups. Group I received high (recruitive) positive end-expiratory pressure (9-20 cm H2O), adjusted as needed; group II received low (supportive) positive end-expiratory pressure (2-6 cm H2O). Sheep in both groups progressively deteriorated and died with cardiocirculatory failure and multiple system organ failure within 12-24 hrs from start of treatment.

CONCLUSIONS

This model of lethal systemic capillary leak syndrome with multiple system organ failure differs greatly from our previous sheep model of acute ventilator-induced lung injury in which sheep were ventilated with a peak inspiratory pressure of 50 cm H2O, a respiratory rate of 4 breaths x min(-1), and an inspiratory time of 1.35 secs, without inducing capillary leak syndrome. The mere change of respiratory rate from 4 to 8 breaths x min(-1), with a near doubling of the inspiratory time to 2.5 secs, although maintaining eucapnia, resulted in lethal systemic capillary leak syndrome and multiple system organ failure with both gross and microscopic pathology of lungs greatly different from our previous model of mechanical ventilation-induced acute respiratory distress syndrome.

Histopathological studies of the acute inflammation in synovial tissue of rat knee joint following intra-articular injection of PLA2 from Chinese Cobra (Naja naja atra) venom

A phospholipase A2 was purified from Chinese Cobra Naja naja atra by a two-step procedure: gel filtration on Superdex 75 and reverse-phase high-performance liquid chromatography (HPLC) on a NUCLEOSIL 5 C18 column. Purified phospholipase A2 was homogeneous, as indicated by capillary electrophoresis and electrospray mass spectrometry. It was a basic protein (pI = 8.2 +/- 0.03) with a molecular mass of 13,258 Da. Amino acid sequence analysis of the N-terminal demonstrated a high degree of homology with other related PLA2 from elapid venoms. The histopathological effects of the purified PLA2 on synovial tissue of knee joint were studied in Wistar rats. Rats were injected intra-articularly with 100 microl solution of PLA2 of different concentrations. Synovial tissue samples with patella were taken for light microscope study. Histopathological evaluation revealed a significant induction of acute inflammation in synovial tissue after injection, as indicated by synovial lining-cell hyperplasia, subsynovial cellular infiltration, and peri-articular soft-tissue cellular infiltration. Marked inflammatory and proliferative changes in synovial tissue were evident after repeated intra-articular injections of 100 microg PLA2. This study failed to show any significant histological changes in cartilage of patella as well as in the surrounding muscle tissue of the knee joints. These results suggest that PLA2 purified from Chinese Cobra venom induce time- and dose-dependent inflammatory changes in the synovial tissue of rat knee joint.

Phospholipase A2: its usefulness in laboratory diagnostics

Phospholipase A2 (PLA2) is an enzyme that catalyzes the hydrolysis of membrane phospholipids. This article reviews the source and structure of PLA2, the involvement of the enzyme in various biological and pathological phenomena, and the usefulness of PLA2 assays in laboratory diagnostics. Of particular importance is the role of PLA2 in the cellular production of mediators of inflammatory response to various stimuli. Assays for PLA2 activity and mass concentration are discussed, and the results of enzyme determinations in plasma from patients with different pathological conditions are presented. The determination of activity and mass concentration in plasma is particularly useful in the diagnosis and prognosis of pancreatitis, multiple organ failure, septic shock, and rheumatoid arthritis. A very important result is the demonstration that PLA2 is an acute phase protein, like CRP. Indeed, there is a close correlation between PLA2 mass concentration and CRP levels in several pathological conditions. Although the determination of C-reactive protein is much easier to perform and is routinely carried out in most clinical laboratories, the assessment of PLA2 activity or mass concentration has to be considered as a reliable approach to obtain a deeper understanding of some pathological conditions and may offer additional information concerning the prognosis of several disorders.

1 alpha,25-Dihydroxyvitamin D3 decreases scalding- and platelet-activating factor-induced high vascular permeability and tissue oedema

We have previously demonstrated that 1,25-dihydroxyvitamin D3 decreases endotoxin-induced mortalities of rat and mouse from 80% and 70% to 14% and 10% (unpublished results). In the present study, pretreatment of 1,25-dihydroxyvitamin D3 decreased pad oedema and pulmonary vascular permeability induced by scalding and platelet-activating factor. 1,25-Dihydroxyvitamin D3 in a dose of 4 x 10(-9) mol/kg decreased pulmonary extravascular Evans blue concentration increased by platelet-activating factor from 6.32 +/- 0.63 ng/g to 2.57 +/- 0.28 ng/g (P < 0.01), and lung water/dry lung weight from 3.79 +/- 0.57 to 1.51 +/- 0.13 (P < 0.01). 1,25-Dihydroxyvitamin D3 of 4 x 10(-11) moles/kg and calcipotriol (a vitamin D analogue which has limited hypercalcaemic effect) of 4 x 10(-9) moles/kg had similar effects. Karyocyte counting of bronchoalveolar lavage fluid and the reduction of mean arterial pressure were also reduced to some extent. These results suggest that 1,25-dihydroxyvitamin D3 may be a new and effective drug to reduce vascular permeability and ameliorate oedema.