Hyperresponsiveness

Asthma is an extremely complex condition characterized by variable and reversible airways obstmction combiaed with nonspecific bronchial hypersensitivity (1 3). The cause of asthma, which is not always readily diagnosed (4), remains unknown. Days, if not weeks, ate needed to document the spontaneous reversal of the airways obstmction ia some patients. Asthmatics experience both an immediate hypersensitivity response and a delayed late-phase reaction, each mediated by a different pathway. Chronic asthma has come to be viewed as an inflammatory disease (5). The late-phase reaction plays a key role ia iaduciag and maintaining the inflammatory state which ia turn is thought to iaduce the bronchial hyperresponsiveness (6). The airways obstmction results from both contraction of airways smooth muscle and excessive bronchial edema. Edema, a characteristic of inflammatory states, is accompanied, ia this case, by the formation of a viscous mucus which can completely block the small airways. 

Theophylline s predominant mode of action appears to be bronchocHlation. However, it has also been shown that prophylactic acHriinistration of theophylline provides some protection from asthma attacks and suppresses the late-phase response (67,68). Some researchers beHeve that at therapeutic semm concentrations theophylline may inhibit the development of airway inflammation (69). There are conflicting reports on the effect of theophylline on allergen-induced bronchial hyperresponsiveness some clinical stucHes report a reduction in hyper-responsiveness, others do not (69,70). Theophylline clearly does not reverse the general bronchial hyperresponsiveness over the course of long-term therapy (71). Because of the relationship between... 

Single dose or short-term treatment with aerosolized steroids inhibits both the late asthmatic response and allergen-induced bronchial hyperresponsiveness (45,92). However it does not affect the early asthmatic response nor does it induce bronchodilation (45,92). Long-term treatment with steroids protects against both the early and late asthmatic responses and also reduces bronchial hyperresponsiveness (44,71,86,93). Over time, the airways relax (dilate) and measures of airway function, such as forced expiratory volume in one second (FEV ), gradually return to almost normal levels. 

Airway hyperresponsiveness is an exaggerated propensity for airways to narrow too easily in response to a wide variety of stimuli. Airway hyperresponsiveness... 

The activation of mast cells by allergen initiates the asthma symptoms within minutes after allergen contact, the early allergic response (EAR), within horns the late allergic response (LAR), and within years and after rqDeated asthma episodes, chronic airway inflammation, airway remodeling, and airway hyperresponsiveness. 

Airway hyperresponsiveness is an exaggerated airway narrowing in response to a variety of unspecific stimuli. It can be measured by bronchial provocation with histamine, methacholine or adenosine. The reason for hyperresponsiveness may be stimulation of sensory nerves that are located within the epithelium. They become easily accessible after denudation of the... 

Bronchial Asthma. Figure 2 Mechanisms of bronchial hyperresponsiveness. Toxic products from eosinophils [cationic peptides, reactive oxygen species (ROS)] cause epithelial injury. Nerve endings become easily accessible to mediators from mast cells, eosinophils [eosinophil-derived neurotoxin (EDN)], and neutrophils, and to airborne toxicants such as S02. Activation of nerve endings stimulates effector cells like mucosal glands and airway smooth muscle either directly or by cholinergic reflexes. 

ROS, reactive oxygen species AHR, airway hyperresponsiveness MMP, matrix metalloprotease. Correlates with cough and chronic bronchitis. bNumber increases with disease severity. 

Asthma is a complex respiratory disorder that involves mast cell degranulation, mucous secretions, and smooth muscle hypertrophy and hyperresponsiveness. Smooth muscle hyperresponsiveness has suggested some defect in the regulation of smooth muscle contractility. Therefore, a number of studies concerning asthma have centered on whether alterations in the regulation of smooth muscle contraction (Figure 4) are responsible for hyperactivity in asthmatic airway smooth muscle. 

Siroux V. Curt F. Oryszczyn MP, Maccario J, Kauff-mann F Role of gender and hormone-related events on IgE. atopy, and eosinophils in the Epidemiological Study on the Genetics and Environment of Asthma, dO bronchial hyperresponsiveness and atopy. J Allergy Clin Immunol 2004 114 491-498. 

AS, Chung KF, Sturton G, Wong SIT, McKenzie AN Blocking IL-25 prevents airway hyperresponsiveness in allergic asthma. J Allergy Clin Immunol 2007 120 1324-1331. 

Miyahara N, Balhorn A, Dakhama A, Gelfand EW 126 IL-lO-treated dendritic cells decrease airway hyperresponsiveness and airway inflammation in mice. J Allergy Clin Immunol 2007 119 1241-1250. 

Rak S. Lowhagen O, Venge P The effect of immunotherapy on bronchial hyperresponsiveness and eosinophil cationic protein in pollen-allergic patients. J Allergy Chn Immunol 1988 82 470-480. 

A logical conclusion from this work was that depression is caused by hyperresponsive )S-adrenoceptors. At first, this might seem to undermine Schildkraut s suggestion that depression is caused by a deficit in noradrenergic transmission. However, proliferation of receptors is the normal response to a deficit in transmitter release and so the opposite change, dowmegulation of jS-adrenoceptors by antidepressants, would follow an increase in the concentration of synaptic noradrenaline. This would be consistent with both their proposed mechanism of action and the monoamine theory for depression. 

The ultimate mode of reduction in function, which, if sufficiently severe, results in death, is blood oxygen desaturation and accumulation of carbon dioxide. However, the inflammatory changes that the insults listed above can evoke and contribute to interference with the perfusion/ventilation relationship are varied and have different expressions in diverse lung disorders bronchial hyperresponsiveness after ozone or nitrous oxide... 

Dusser, D.J., Jacoby, D.B., Djokic, T.D., Borson, D.B. and Nadel J.A. (1989). Virus induces airway hyperresponsiveness to taehykinins by decreasing neutral endopeptidase. Am. Rev. Resp. Dis. 139, A352. 

Gordon, T., Sheppard, D., McDonald, D., Distefano, S. and Scypinski, L. (1985). Airway hyperresponsiveness and inOam-mation induced by toluene diisocyanate in guinea-pigs. Am. Rev. Resp. Dis. 132, 1106-1112. 

Mohsenin, V. (1987). Effect of vitamin C on nitrogen dioxide induced hyperresponsiveness in normal subjects. Am. Rev. Resp. Dis. 136, 1408-1411. 

Yeadon, M., Wilkinson, D. and Payne, A.N. (1990). Ozone induces bronchial hyperresponsiveness to inhaled substance P through functional inhibition of enkephalinase. Br. J. Pharmacol. 99, 191P. 

BCF Basophil chemotactic factor B-CFC Basophil colony-forming cell BCG Bacillus Calmette-Guerin BCNU l,3-bis(2-chloroethyl)-l-nitrosourea bFGF Basic fibroblast growth fiictor Bg Birbeck granules BHR Bronchial hyperresponsiveness BHT Butylated hydroxyroluene b.i.d. Bis in die (twice a day)... 

Other therapeutic uses of cannabinoid agonists have been reported. The potential of cannabinoids as a treatment for asthma is supported experimentally. A CBi agonist, (i )-methanandamide (21), inhibited nerve growth factor (NGF)-induced airway hyperresponsiveness in vivo [251]. The antipruritic effect of cannabinoids has been reported, the action being mediated by both CBi and CB2 pathways [252]. Treatment with cannabis extract improved urinary tract symptoms of multiple sclerosis patients significantly in an open-label pilot study [253]. 

Asthma is characterized by inflammation, airway hyperresponsiveness (AHR), and airway obstruction. Inhaled antigens... 

In the late phase response, activated airway cells release inflammatory cytokines and chemokines, recruiting inflammatory cells into the lungs. The late phase response occurs 4 to 6 hours after the initial allergen challenge and results in a less intense bronchoconstriction as well as increased airway hyperresponsiveness and airway inflammation.6... 

Airway hyperresponsiveness is defined as the exaggerated ability of the airways to narrow in response to a variety of stimuli. Although AHR exists in patients without asthma, it is a characteristic feature of asthma and appears to be directly related to airway inflammation and the severity of asthma.1,3 Treatment of airway inflammation with inhaled corticosteroids attenuates AHR in asthma but does not eliminate it.1 Clinically, AHR manifests as increased variability of airway function. Although not commonly used to diagnose asthma, AHR can be evaluated clinically using a methacholine or histamine bronchoprovocation test. 

Neuropathic pain is defined as spontaneous pain and hypersensitivity to pain associated with damage to or pathologic changes in the peripheral nervous system as in painful diabetic peripheral neuropathy (DPN), acquired immunodeficiency syndrome (AIDS), polyneuropathy, post-herpetic neuralgia (PHN) or pain originating in the central nervous system (CNS), that which occurs with spinal cord injury, multiple sclerosis, and stroke. Functional pain, a relatively newer concept, is pain sensitivity due to an abnormal processing or function of the central nervous system in response to normal stimuli. Several conditions considered to have this abnormal sensitivity or hyperresponsiveness include fibromyalgia and irritable bowel syndrome. 

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