Anthracopoulos Michael B, Everard Mark L
Respiratory Unit, Department of Paediatrics, University of Patras, Patras, Greece.
Division of Paediatrics & Child Health, Perth Children's Hospital, University of Western Australia, Perth, WA, Australia.
Front Pediatr. 2020 Apr 16;8:95. doi: 10.3389/fped.2020.00095. eCollection 2020.
The defining feature of asthma is loss of normal post-natal homeostatic control of airways smooth muscle (ASM). This is the key feature that distinguishes asthma from all other forms of respiratory disease. Failure to focus on impaired ASM homeostasis largely explains our failure to find a cure and contributes to the widespread excessive morbidity associated with the condition despite the presence of effective therapies. The mechanisms responsible for destabilizing the normal tight control of ASM and hence airways caliber in post-natal life are unknown but it is clear that atopic inflammation is neither necessary nor sufficient. Loss of homeostasis results in excessive ASM contraction which, in those with , is manifest by variations in airflow resistance over periods of time. During viral , the ability to respond to bronchodilators is partially or almost completely lost, resulting in ASM being "locked down" in a contracted state. Corticosteroids appear to restore normal or near normal homeostasis in those with poor control and restore bronchodilator responsiveness during exacerbations. The mechanism of action of corticosteroids is unknown and the assumption that their action is solely due to "anti-inflammatory" effects needs to be challenged. ASM, in evolutionary terms, dates to the earliest land dwelling creatures that required muscle to empty primitive lungs. ASM appears very early in embryonic development and active peristalsis is essential for the formation of the lungs. However, in post-natal life its only role appears to be to maintain airways in a configuration that minimizes resistance to airflow and dead space. In health, significant constriction is actively prevented, presumably through classic negative feedback loops. Disruption of this robust homeostatic control can develop at any age and results in asthma. In order to develop a cure, we need to move from our current focus on immunology and inflammatory pathways to work that will lead to an understanding of the mechanisms that contribute to ASM stability in health and how this is disrupted to cause asthma. This requires a radical change in the focus of most of "asthma research."
哮喘的决定性特征是出生后气道平滑肌(ASM)失去正常的稳态控制。这是将哮喘与所有其他形式的呼吸系统疾病区分开来的关键特征。未能关注ASM稳态受损在很大程度上解释了我们未能找到治愈方法的原因,并且尽管有有效的治疗方法,但仍导致了与该疾病相关的广泛过度发病。导致出生后ASM正常严格控制以及气道管径不稳定的机制尚不清楚,但很明显,特应性炎症既不是必需的,也不是充分的。稳态丧失会导致ASM过度收缩,在哮喘患者中,这表现为气流阻力在一段时间内的变化。在病毒感染期间,对支气管扩张剂的反应能力会部分或几乎完全丧失,导致ASM“锁定”在收缩状态。皮质类固醇似乎能在控制不佳的患者中恢复正常或接近正常的稳态,并在病情加重期间恢复支气管扩张剂反应性。皮质类固醇的作用机制尚不清楚,其作用仅归因于“抗炎”作用的假设需要受到质疑。从进化角度来看,ASM可追溯到最早的陆地生物,这些生物需要肌肉来排空原始肺部。ASM在胚胎发育早期就出现了,活跃的蠕动对肺部的形成至关重要。然而,在出生后的生活中,它唯一的作用似乎是维持气道处于使气流阻力和死腔最小化的形态。在健康状态下,可能通过经典的负反馈回路积极防止显著的收缩。这种强大的稳态控制的破坏可在任何年龄发生,并导致哮喘。为了找到治愈方法,我们需要从目前对免疫学和炎症途径的关注转向能够导致理解有助于健康状态下ASM稳定性的机制以及这种稳定性如何被破坏而导致哮喘的研究。这需要对大多数“哮喘研究”的重点进行彻底改变。