A role for transient receptor potential ankyrin 1 cation channel (TRPA1) in airway hyper-responsiveness?

Airway smooth muscle (ASM) contraction controls the airway caliber. Airway narrowing is exaggerated in obstructive lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD). The mechanism by which ASM tone is dysregulated in disease is not clearly understood. Recent research on ion channels, particularly transient receptor potential cation channel, subfamily A, member 1 (TRPA1), is uncovering new understanding of altered airway function. TRPA1, a member of the TRP channel superfamily, is a chemo-sensitive cation channel that can be activated by a variety of external and internal stimuli, leading to the influx of Ca(2+). Functional TRPA1 channels have been identified in neuronal and non-neuronal tissues of the lung, including ASM. In the airways, these channels can regulate the release of mediators that are markers of airway inflammation in asthma and COPD. For, example, TRPA1 controls cigarette-smoke-induced inflammatory mediator release and Ca(2+) mobilization in vitro and in vivo, a response tied to disease pathology in COPD. Recent work has revealed that pharmacological or genetic inhibition of TRPA1 inhibits the allergen-induced airway inflammation in vitro and airway hyper-responsiveness (AHR) in vivo. Collectively, it appears that TRPA1 channels may be determinants of ASM contractility and local inflammation control, positioning them as part of novel mechanisms that control (patho)physiological function of airways and ASM.

Chronic exposure to perfluorinated compounds: Impact on airway hyperresponsiveness and inflammation.

Emerging epidemiological evidence reveals a link between lung disease and exposure to indoor pollutants such as perfluorinated compounds (PFCs). PFC exposure during critical developmental stages may increase asthma susceptibility. Thus, in a murine model, we tested the hypothesis that early life and continued exposure to two ubiquitous household PFCs, perfluorooctanoic acid (PFOA) and perflurooctanesulfonic acid (PFOS), can induce lung dysfunction that exacerbates allergen-induced airway hyperresponsiveness (AHR) and inflammation. Balb/c mice were exposed to PFOA or PFOS (4 mg/kg chow) from gestation day 2 to 12 wk of age by feeding pregnant and nursing dams, and weaned pups. Some pups were also sensitized and challenged with ovalbumin (OVA). We assessed lung function and inflammatory cell and cytokine expression in the lung and examined bronchial goblet cell number. PFOA, but not PFOS, without the OVA sensitization/challenge induced AHR concomitant with a 25-fold increase of lung macrophages. PFOA exposure did not affect OVA-induced lung inflammatory cell number. In contrast, PFOS exposure inhibited OVA-induced lung inflammation, decreasing total cell number in lung lavage by 68.7%. Interferon-γ mRNA in the lung was elevated in all PFC-exposed groups. Despite these effects, neither PFOA nor PFOS affected OVA-induced AHR. Our data do not reveal PFOA or PFOS exposure as a risk factor for more severe allergic asthma-like symptoms, but PFOA alone can induce airway inflammation and alter airway function.

Prophylactic benefits of systemically delivered simvastatin treatment in a house dust mite challenged murine model of allergic asthma.

BACKGROUND AND PURPOSE: Systemically delivered statins can blunt airway inflammation in ovalbumin-challenged mice. However, in asthma clinical trials the beneficial effects of introducing oral statins are not compelling. We have invetigated this discrepancy using a clinically relevant murine model of allergic asthma, and by including a prophylactic study arm. EXPERIMENTAL APPROACH: Adult mice were: 1) challenged with house dust mite (HDM) alone or with subcutaneous (s.c.) simvastatin for two weeks; or 2) also treated with simvastatin for one week prior to HDM challenge. We assayed lung function, inflammatory cell influx and cytokine profile, goblet cell abundance, and simvastatin concentration in serum, lung lavage and tissue. KEY RESULTS: Ultrahigh performance liquid chromatography-tandem mass spectrometry revealed that pharmacologically active simvastatin reached peak serum concentration after 8 h, but declined rapidly. Prophylactic treatment doubled peak serum simvastatin and repeated s.c. delivery established stable serum levels, but simvastatin was undetectable in the lungs. Both simvastatin treatment arms suppressed indices of HDM-induced airway inflammation and goblet cell hyperplasia, but this was significantly greater with prophylactic therapy, in particular, inhibition of neutrophil and eosinophil influx, and cytokine accumulation. Conversely, neither acute nor prophylactic delivery of simvastatin prevented HDM challenge-induced airway hyperreactivity. CONCLUSION AND IMPLICATIONS: Systemically administered simvastatin accumulates in the blood, but not in lung tissues, and reduces leukocyte influx and associated lung inflammation. Prophylactic therapy has the greatest anti-inflammatory effects, but as observed in human clinical trials, systemic simvastatin therapy does not prevent allergic airway hyperreactivity.

Epithelium-dependent modulation of responsiveness of airways from caveolin-1 knockout mice is mediated through cyclooxygenase-2 and 5-lipoxygenase.

BACKGROUND AND PURPOSE: Acute silencing of caveolin-1 (Cav-1) modulates receptor-mediated contraction of airway smooth muscle. Moreover, COX-2- and 5-lipoxygenase (5-LO)-derived prostaglandin and leukotriene biosynthesis can influence smooth muscle reactivity. COX-2 half-life can be prolonged through association with Cav-1. We suggested that lack of Cav-1 modulated levels of COX-2 which in turn modulated tracheal contraction, when arachidonic acid signalling was disturbed by inhibition of COX-2. EXPERIMENTAL APPROACH: Using tracheal rings from Cav-1 knockout (KO) and wild-type mice (B6129SF2/J), we measured isometric contractions to methacholine and used PCR, immunoblotting and immunohistology to monitor expression of relevant proteins. KEY RESULTS: Tracheal rings from Cav-1 KO and wild-type mice exhibited similar responses, but the COX-2 inhibitor, indomethacin, increased responses of tracheal rings from Cav-1 KO mice to methacholine. The phospholipase A2 inhibitor, eicosatetraynoic acid, which inhibits formation of both COX-2 and 5-LO metabolites, had no effect on wild-type or Cav-1 KO tissues. Indomethacin-mediated hyperreactivity was ablated by the LTD4 receptor antagonist (montelukast) and 5-LO inhibitor (zileuton). The potentiating effect of indomethacin on Cav-1 KO responses to methacholine was blocked by epithelial denudation. Immunoprecipitation showed that COX-2 binds Cav-1 in wild-type lungs. Immunoblotting and qPCR revealed elevated levels of COX-2 and 5-LO protein, but not COX-1, in Cav-1 KO tracheas, a feature that was prevented by removal of the epithelium. CONCLUSION AND IMPLICATIONS: The indomethacin-induced hypercontractility observed in Cav-1 KO tracheas was linked to increased expression of COX-2 and 5-LO, which probably enhanced arachidonic acid shunting and generation of pro-contractile leukotrienes when COX-2 was inhibited.

Comparative outcome between chemoradiotherapy and lateral pelvic lymph node dissection following total mesorectal excision in rectal cancer.

OBJECTIVE: To evaluate comparative outcome between adjuvant postoperative chemoradiotherapy (postoperative CRT) and lateral pelvic lymph node dissection (LPLD) following total mesorectal excision (TME) in rectal cancer patients. BACKGROUND: Although TME results in lower rate of locoregional recurrence compared with conventional surgery, these 2 treatment modalities following TME have not adequately been appraised until the present trend of preoperative chemoradiotherapy. PATIENTS AND METHODS: Between 1995 and 2000, patients with stage II and III rectal cancer underwent TME plus postoperative CRT (n = 309) or LPLD (n = 176). Patients in the postoperative CRT group received 8 cycles of 5-fluorouracil plus leucovorin and 45 Gy pelvic radiotherapy. Patients in the LPLD group underwent lateral lymph node dissection outside the pelvic plexus. RESULTS: The 5-year overall and disease-free survival rates were 78.3% and 67.3% in the postoperative CRT group, respectively, and 73.9% and 68.6% in the LPLD group, respectively, without significant differences between these groups. Patients in the LPLD group with stage III lower rectal cancer had a locoregional recurrence rate 2.2-fold greater than those in the postoperative CRT group (16.7% vs. 7.5%, P = 0.044). Multivariate analysis showed that APR and advanced T-category (T4) were significantly associated with locoregional recurrence, whereas lymph node metastases, high preoperative serum carcinoembryonic antigen, and APR were significantly associated with shortening of disease-free survival. CONCLUSIONS: Postoperative-CRT and LPLD following TME resulted in comparable survival rates, but the locoregional recurrence rate was higher in the LPLD group. These findings suggest that initial surgery is appropriate for rectal cancer patients who are candidates for low anterior resection without extensive local disease (T1-T3), regardless of lymph node status.

Hepatic arterial infusion alternating with systemic chemotherapy in patients with non-resectable hepatic metastases from colorectal cancer.

BACKGROUND AND AIM: Hepatic arterial infusion (HAI) chemotherapy has a number of limitations, including a low rate of complete response and frequent extrahepatic recurrence, in colorectal cancer patients with non-resectable hepatic metastases. METHODS: Twenty-nine colorectal cancer patients with non-resectable hepatic metastases were consecutively enrolled for HAI alternating with systemic chemotherapy (HA + SC group). The protocol comprised six cycles of alternating HAI (5-FU + leucovorin for 14 days, and mitomycin C on the first day) and systemic chemotherapy (5-FU + leucovorin). Colorectal cancer patients with two or more hepatic metastases treated using hepatic resection and systemic chemotherapy (HR + SC group) were selected as a comparative group. RESULTS: Within the HA + SC group, complete response was achieved in eight patients (28%), whereas 13 patients (45%) showed progressive disease. Six of the eight patients with complete response lived for more than 38 months. Extrahepatic recurrences were more frequent in the HR + SC group than the HA + SC group (47 vs 21%, P = 0.024). The two groups did not differ with respect to overall and hepatic progression-free survival (P = 0.947 and 0.444, respectively), displaying median +/- SE values of 38 +/- 7 and 20 +/- 3 months in the HA + SC group, and 39 +/- 9 and 33 +/- 14 months in the HR + SC group, respectively. One patient in each group experienced toxic hepatitis, and sclerosing cholangitis occurred in one patient of the HA + SC group. Other complications were mostly grade 1 or 2. CONCLUSIONS: HAI alternating with systemic chemotherapy led to a promising response and hepatic progression-free survival, possibly reducing extrahepatic recurrence in colorectal cancer patients with non-resectable liver metastases.