ABSTRACT
Low-level laser therapy (LLLT) controls bronchial hyperresponsiveness (BHR) associated with increased RhoA expression as well as pro-inflammatory mediators associated with NF-kB in acute lung inflammation. Herein, we explore if LLLT can reduce both BHR and Th2 cytokines in allergic asthma. Mice were studied for bronchial reactivity and lung inflammation after antigen challenge. BHR was measured through dose-response curves to acetylcholine. Some animals were pretreated with a RhoA inhibitor before the antigen. LLLT (660 nm, 30 mW and 5.4 J) was applied on the skin over the right upper bronchus and two irradiation protocols were used. Reduction of BHR post LLLT coincided with lower RhoA expression in bronchial muscle as well as reduction in eosinophils and eotaxin. LLLT also diminished ICAM expression and Th2 cytokines as well as signal transducer and activator of transduction 6 (STAT6) levels in lungs from challenged mice. Our results demonstrated that LLLT reduced BHR via RhoA and lessened allergic lung inflammation via STAT6.
Subject(s)
Airway Remodeling/radiation effects , Asthma/radiotherapy , Bronchoconstriction/radiation effects , Cytokines/metabolism , Hypersensitivity/radiotherapy , Low-Level Light Therapy , Airway Remodeling/drug effects , Airway Remodeling/physiology , Amides/pharmacology , Animals , Asthma/drug therapy , Asthma/physiopathology , Bronchi/drug effects , Bronchi/physiopathology , Bronchi/radiation effects , Bronchial Hyperreactivity/drug therapy , Bronchial Hyperreactivity/physiopathology , Bronchial Hyperreactivity/radiotherapy , Bronchoconstriction/drug effects , Bronchoconstriction/physiology , Enzyme Inhibitors/pharmacology , Hypersensitivity/drug therapy , Hypersensitivity/physiopathology , Lung/drug effects , Lung/physiopathology , Lung/radiation effects , Male , Mice , Mice, Inbred BALB C , Muscle, Smooth/drug effects , Muscle, Smooth/physiopathology , Muscle, Smooth/radiation effects , Ovalbumin/adverse effects , Pneumonia/drug therapy , Pneumonia/physiopathology , Pneumonia/radiotherapy , Pyridines/pharmacology , STAT6 Transcription Factor/metabolism , rho GTP-Binding Proteins/antagonists & inhibitors , rho GTP-Binding Proteins/metabolism , rhoA GTP-Binding ProteinABSTRACT
The precision-cut lung slice (PCLS) technique is widely used to examine airway responses in different species. We developed a method to study nerve-dependent bronchoconstriction by the application of electric field stimulation (EFS) to PCLS. PCLS prepared from Wistar rats were placed between two platinum electrodes to apply serial rectangular impulses (5-100 Hz), and bronchoconstriction was studied by videomicroscopy. The extent of airway contractions increased with higher frequencies. Stable repeated airway contractions were obtained at a frequency of 50 Hz, a width of 1 ms, and an output of 200 mA for 2.5 s each minute. Larger airways showed stronger responses. The EFS-triggered contractions were increased by the acetylcholine esterase inhibitor neostigmine (10 µM) and reversed by the muscarinic antagonist atropine (10 µM), whereas the thromboxane protanoid receptor antagonist SQ29548 (10 µM) had no effect. Magnesium ions (10 mM) antagonized airway contractions induced by EFS, but not by methacholine, indicating that nerve endings remain intact in PCLS. Our data further show that the electrically evoked airway contractions in PCLS are mediated by cholinergic nerves, independent of thromboxane and more prominent in larger airways. Taken together these findings show that nerve endings remain intact in PCLS, and they suggest that the present method is useful to study neurogenic responses in airways of different size.
