Infection by Toxoplasma gondii, a severe parasite in neonates and AIDS patients, causes impaired anion secretion in airway epithelia.

The airway epithelia initiate and modulate the inflammatory responses to various pathogens. The cystic fibrosis transmembrane conductance regulator-mediated Cl(-) secretion system plays a key role in mucociliary clearance of inhaled pathogens. We have explored the effects of Toxoplasma gondii, an opportunistic intracellular protozoan parasite, on Cl(-) secretion of the mouse tracheal epithelia. In this study, ATP-induced Cl(-) secretion indicated the presence of a biphasic short-circuit current (Isc) response, which was mediated by a Ca(2+)-activated Cl(-) channel (CaCC) and the cystic fibrosis transmembrane conductance regulator. However, the ATP-evoked Cl(-) secretion in T. gondii-infected mouse tracheal epithelia and the elevation of [Ca(2+)]i in T. gondii-infected human airway epithelial cells were suppressed. Quantitative reverse transcription-PCR revealed that the mRNA expression level of the P2Y2 receptor (P2Y2-R) increased significantly in T. gondii-infected mouse tracheal cells. This revealed the influence that pathological changes in P2Y2-R had on the downstream signal, suggesting that P2Y2-R was involved in the mechanism underlying T. gondii infection in airways. These results link T. gondii infection as well as other pathogen infections to Cl(-) secretion, via P2Y2-R, which may provide new insights for the treatment of pneumonia caused by pathogens including T. gondii.

Relaxant Effect of Sodium Tanshinone IIA Sulphonate on Mouse Tracheal Smooth Muscle.

Sodium tanshinone IIA sulphonate, a water-soluble derivative of tanshinone IIA, has been proven to possess versatile biological properties, but its pharmacological effect on tracheal smooth muscle remains elusive. This paper presents a study on the relaxant effect and underlying mechanisms of sodium tanshinone IIA sulphonate on mouse tracheal smooth muscle. The relaxant effect of sodium tanshinone IIA sulphonate was evaluated in mouse tracheal rings using a mechanical recording system. Intracellular Ca2+ concentration was measured in primary cultured tracheal smooth muscle cells using confocal imaging system. The results showed that sodium tanshinone IIA sulphonate induced dose-dependent relaxation of mouse tracheal rings in a ß-adrenoceptor- and epithelium-independent manner. Pretreatment with the ATP-sensitive K+ channel blocker glibenclamide partly attenuated the relaxation response. Administration of sodium tanshinone IIA sulphonate notably inhibited the extracellular Ca2+-induced contraction. High KCl or carbachol-evoked elevation in the intracellular Ca2+ concentration was also abrogated by sodium tanshinone IIA sulphonate in tracheal smooth muscle cells. In conclusion, the tracheal relaxant effect of sodium tanshinone IIA sulphonate was independent of ß-adrenoceptor and airway epithelium, mediated primarily by inhibition of extracellular Ca2+ influx via L-type voltage-dependent Ca2+ channels and partially by activation of the ATP-sensitive K+ channel. These results indicate the potential therapeutic value of sodium tanshinone IIA sulphonate for asthma treatment.

[The role of extracellular ATP in the airway].

ATP serves not only as an energy source for all cell types but as an extracellular messenger for autocrine and paracrine signaling involving in a versatile role in modulating various cellular functions. This review summarizes the efflux pathways of ATP released from airway epithelial cells, the signal pathways through which ATP induces ion transport by the epithelia of airway, as well as its epithelium-dependent modulation of smooth muscle contraction of airway and the mechanism underlying in airway diseases.

Increased intracellular Cl- concentration promotes ongoing inflammation in airway epithelium.

Airway epithelial cells harbor the capacity of active Cl- transepithelial transport and play critical roles in modulating innate immunity. However, whether intracellular Cl- accumulation contributes to relentless airway inflammation remains largely unclear. This study showed that, in airway epithelial cells, intracellular Cl- concentration ([Cl-]i) was increased after Pseudomonas aeruginosa lipopolysaccharide (LPS) stimulation via nuclear factor-κB (NF-κB)-phosphodiesterase 4D (PDE4D)-cAMP signaling pathways. Clamping [Cl-]i at high levels or prolonged treatment with LPS augmented serum- and glucocorticoid-inducible protein kinase 1 (SGK1) phosphorylation and subsequently triggered NF-κB activation in airway epithelial cells, whereas inhibition of SGK1 abrogated airway inflammation in vitro and in vivo. Furthermore, Cl--SGK1 signaling pathway was pronouncedly activated in patients with bronchiectasis, a chronic airway inflammatory disease. Conversely, hydrogen sulfide (H2S), a sulfhydryl-containing gasotransmitter, confers anti-inflammatory effects through decreasing [Cl-]i via activation of cystic fibrosis transmembrane conductance regulator (CFTR). Our study confirms that intracellular Cl- is a crucial mediator of sustained airway inflammation. Medications that abrogate excessively increased intracellular Cl- may offer novel targets for the management of airway inflammatory diseases.

Cellular mechanism underlying hydrogen sulfide induced mouse tracheal smooth muscle relaxation: role of BKCa.

Recent studies have suggested that hydrogen sulfide (H2S), an important endogenous signaling gaseous molecule, participates in relaxation of smooth muscle. Nevertheless, the mechanism of this relaxation effect on respiratory system is still unclear. The present study aims to investigate the physiological function as well as cellular mechanism of H2S in tracheal smooth muscle. Application of the H2S donor, sodium hydrosulphide (NaHS) and the precursor of H2S, l-cysteine (l-Cys) induced mouse tracheal smooth muscle (TSM) relaxation in an epithelium-independent manner. The relaxation of TSM induced by NaHS was abrogated by iberiotoxin (IbTX), the large conductance calcium activated potassium channel (BKCa) blocker. In primary cultured mouse TSM cells, NaHS remarkably increased potassium outward currents in whole-cell patch clamp, hyperpolarized TSM cells and inhibited the calcium influx. All of these effects were significantly blocked by IbTX. Consistent with the results in vitro, administration of NaHS in vivo also reduced airway hyperresponsiveness in Ovalbumin (OVA)-challenged asthmatic mice. Our present study indicates that NaHS can induce mouse TSM relaxation by activating BKCa. These observations reveal the physiological function of H2S in airway, which provides a promising pharmacological target for the treatment of asthma and other respiratory diseases associated with over-contraction of TSM.

Cellular mechanism underlying formaldehyde-stimulated Cl- secretion in rat airway epithelium.

BACKGROUND: Recent studies suggest that formaldehyde (FA) could be synthesized endogeneously and transient receptor potential (TRP) channel might be the sensor of FA. However, the physiological significance is still unclear. METHODOLOGY/PRINCIPAL FINDINGS: The present study investigated the FA induced epithelial Cl(-) secretion by activation of TRPV-1 channel located in the nerve ending fiber. Exogenously applied FA induced an increase of I(SC) in intact rat trachea tissue but not in the primary cultured epithelial cells. Western blot and immunofluorescence analysis identified TRPV-1 expression in rat tracheal nerve ending. Capsazepine (CAZ), a TRPV-1 specific antagonist significantly blocked the I(SC) induced by FA. The TRPV-1 agonist capsaicin (Cap) induced an increase of I(SC), which was similar to the I(SC) induced by FA. L-703606, an NK-1 specific inhibitor and propranolol, an adrenalin ß receptor inhibitor significantly abolished the I(SC) induced by FA or Cap. In the ion substitute analysis, FA could not induce I(SC) in the absence of extracelluar Cl(-). The I(SC) induced by FA could be blocked by the non-specific Cl(-) channel inhibitor DPC and the CFTR specific inhibitor CFTR(i-172), but not by the Ca(2+)-activated Cl(-) channel inhibitor DIDS. Furthermore, both forskolin, an agonist of adenylate cyclase (AC) and MDL-12330A, an antagonist of AC could block FA-induced I(SC). CONCLUSION: Our results suggest that FA-induced epithelial I(SC) response is mediated by nerve, involving the activation of TRPV-1 and release of adrenalin as well as substance P.

[Construction of the life cycle of Angiostrongylus cantonensis in laboratory].

OBJECTIVE: To construct the life cycle of Angiostrongylus cantonensis (A.cantonensis) in laboratory condition. METHODS: SD rats were infected orally with the third-stage larvae of A.cantonensis collected from Jiangmen, Guangdong province. Six weeks after infection, the first-stage larvae were isolated from fresh feces of the rats by using Baermann funnel to infect 25 second-generation white jade snails raised in laboratory at the daily dose of 300 000 for 3 consecutive days. Three weeks later, the snails were dissected for counting the third-staged larvae of A.cantonensis, and those positive for A.cantonensis infection were fed directly to 10 fasting rats. The serum samples of the rats were then collected 2 weeks later for examination of specific antibodies using ELISA. The feces of the infected rats were examined microscopically after 6 weeks, and the brain, heart and lungs of the infected rats were dissected to observe the larvae at 3, 5, and 8 weeks, respectively. RESULTS: The 3-stage larvae of A.cantonensis were found in the second-generation snails 3 weeks after infection. The positivity rate of serum specific antibodies was 100% in the 10 rats 2 weeks after feeding of the infected snails. The 1-stage larvae were detected in the feces of the rats 6 weeks after infection, and the fourth-stage larvae were found in the brain of the rats at 3 weeks, while adult worm and eggs were found in the heart and lungs of the infected rats at 5 and 8 weeks. CONCLUSION: The successful establishment of human colon carcinoma cell line with PRL-3 gene knock-down provide a basis for investigation of the role of PRL-3 gene in the metastasis of human colorectal carcinoma.