Deficiency of surfactant in alveoli leads to increased resistance to breathing. Histamine is a mediator in allergic respiratory diseases. Though the bronchoconstrictor effect of histamine is well recognised, histamine may have additional actions that contribute to pathogenesis in these diseases. The present study aimed to observe the effect of histamine on lecithin, a major component of alveolar surfactant. Lecithin content in broncho-alveolar lavage (BAL) fluid of healthy adult male rats was estimated by enzymatic method using Boehringer-Mannheim kits. Lecithin content in these control animals was compared with that in three groups of healthy adult male rats following subcutaneous administration of 0.06 mg of histamine diphosphate at 10 minutes, 30 minutes and 60 minutes intervals, respectively. A significant reduction in lecithin levels in BAL fluid was observed up to one hour after administration of histamine. The results indicate a possible additional action of histamine in the pathogenesis of allergic respiratory diseases.
Lecithin, a major surface active substance of the surfactant system of the lung, was estimated in broncho-alveolar lavage (BAL) fluid in four groups of healthy adult male albino rats. Rats from group I were not administered any drug and acted as controls. Group II were administered histamine diphosphate. Group III were given H1 blocker (pyrilamine maleate) followed by histamine diphosphate. Group IV received H2 blocker (ranitidine hydrochloride) followed by histamine diphosphate. Lecithin content of BAL fluid in the control group was compared with that in the other three groups. A significant decrease in lecithin content was observed in the rats that received either histamine diphosphate or H1 blocker followed by histamine diphosphate. However, compared to control rats no significant difference in lecithin content was seen in rats that received H2 blocker followed by histamine diphosphate. The results clearly indicate that the decrease in surface active lecithin content in BAL fluid following administration of histamine diphosphate was unaffected by prior administration of H1 blocker, but was blocked by prior administration of H2 blocker. It was concluded that histamine induced decrease in lecithin content of BAL fluid is mediated through H2 receptors. Since the predominant source of intra-alveolar lecithin are Type II cells of the alveolar epithelium, It is possible that Type II cells have H2 receptors, stimulation of which resulted in decreased intraalveolar lecithin.
Asthma has affected more than 300 million people worldwide and is considered one of the most debilitating global public health problems based on a recent statistical report from the Global Initiative for Asthma. Inflammation of the airways leads to the various interrelated mechanisms of innate and adaptive immunity acting mutually with the epithelium of the respiratory organ. Fucoxanthin is an orange or brown pigment which is naturally found in various seaweeds. To the best of our knowledge, there are no scientific claims or evidence of the curative effects of fucoxanthin against asthma. Hence, this present research was designed to investigate the curative activity of fucoxanthin against ovalbumin-induced asthma in a mouse model. Fucoxanthin (50 mg/kg) showed significant (P < 0.001) antiasthma activity. It effectively decreased intracellular secretion of reactive oxygen species and increased antioxidant enzyme activity. Fucoxanthin also decreased inflammatory cytokine markers in bronchoalveolar lavage fluid. Because fucoxanthin showed effective antiasthma activity against ovalbumin-induced asthma in experimental animals, further research on this natural antioxidant could lead to development of a novel drug for the treatment of asthma in humans.
Andrographolide (AGP) and 14-deoxy-11,12-didehydroandrographolide (DDAG), two main diterpenoid constituents of Andrographis paniculata were previously shown to ameliorate asthmatic symptoms in a mouse model. However, due to inadequacies of both compounds in terms of drug-likeness, DDAG analogues were semisynthesised for assessment of their anti-asthma activity. A selected analogue, 3,19-diacetyl-14-deoxy-11,12-didehydroandrographolide (SRS27), was tested for inhibitory activity of NF-κB activation in TNF-α-induced A549 cells and was subsequently evaluated in a mouse model of ovalbumin (OVA)-induced asthma. Female BALB/c mice, 6-8weeks old were sensitized on days 0 and 14, and challenged on days 22, 23 and 24 with OVA. Compound or vehicle (3% dimethyl sulfoxide) was administered intraperitoneally 1h before and 11h after each OVA aerosol challenge. On day 25, pulmonary eosinophilia, airway hyperresponsiveness, mucus hypersecretion, inflammatory cytokines such as IL-4, -5 and -13 in BAL fluid, gene expression of inflammatory mediators such as 5-LOX, E-selectin, VCAM-1, CCL5, TNF-α, AMCase, Ym2, YKL-40, Muc5ac, CCL2 and iNOS in animal lung tissues, and serum IgE were determined. SRS27 at 30μM was found to suppress NF-κB nuclear translocation in A549 cells. In the ovalbumin-induced mouse asthma model, SRS27 at 3mg/kg displayed a substantial decrease in pulmonary eosinophilia, BAL fluid inflammatory cytokines level, serum IgE production, mucus hypersecretion and gene expression of inflammatory mediators in lung tissues. SRS27 is the first known DDAG analogue effective in ameliorating inflammation and airway hyperresponsiveness in the ovalbumin-induced mouse asthma model.