National Institute for Biostructures and Biosystems (NIBB), Rome, Italy.
Department of Food and Drug Science, University of Parma, Parma, Italy.
Front Neural Circuits. 2022 Apr 25;16:862005. doi: 10.3389/fncir.2022.862005. eCollection 2022.
Chemosensory systems are deemed marginal in human pathology. In appraising their role, we aim at suggesting a paradigm shift based on the available clinical and experimental data that will be discussed. Taste and olfaction are polymodal sensory systems, providing inputs to many brain structures that regulate crucial visceral functions, including metabolism but also endocrine, cardiovascular, respiratory, and immune systems. Moreover, other visceral chemosensory systems monitor different essential chemical parameters of "milieu intérieur," transmitting their data to the brain areas receiving taste and olfactory inputs; hence, they participate in regulating the same vital functions. These chemosensory cells share many molecular features with olfactory or taste receptor cells, thus they may be affected by the same pathological events. In most COVID-19 patients, taste and olfaction are disturbed. This may represent only a small portion of a broadly diffuse chemosensory incapacitation. Indeed, many COVID-19 peculiar symptoms may be explained by the impairment of visceral chemosensory systems, for example, silent hypoxia, diarrhea, and the "cytokine storm". Dysregulation of chemosensory systems may underlie the much higher mortality rate of COVID-19 Acute Respiratory Distress Syndrome (ARDS) compared to ARDSs of different origins. In chronic non-infectious diseases like hypertension, diabetes, or cancer, the impairment of taste and/or olfaction has been consistently reported. This may signal diffuse chemosensory failure, possibly worsening the prognosis of these patients. Incapacitation of one or few chemosensory systems has negligible effects on survival under ordinary life conditions but, under stress, like metabolic imbalance or COVID-19 pneumonia, the impairment of multiple chemosensory systems may lead to dire consequences during the course of the disease.
化学感觉系统在人类病理学中被认为是次要的。在评估它们的作用时，我们旨在基于将讨论的现有临床和实验数据提出一个范式转变。味觉和嗅觉是多模态感觉系统，为调节包括代谢在内的重要内脏功能的许多大脑结构提供输入，还包括内分泌、心血管、呼吸和免疫系统。此外，其他内脏化学感觉系统监测“内环境”的不同基本化学参数，并将其数据传输到接收味觉和嗅觉输入的大脑区域；因此，它们参与调节相同的重要功能。这些化学感觉细胞与嗅觉或味觉受体细胞具有许多共同的分子特征，因此它们可能受到相同的病理事件的影响。在大多数 COVID-19 患者中，味觉和嗅觉受到干扰。这可能只是广泛弥漫性化学感觉障碍的一小部分。事实上，许多 COVID-19 特殊症状可以通过内脏化学感觉系统的损伤来解释，例如，无声缺氧、腹泻和“细胞因子风暴”。化学感觉系统的失调可能是 COVID-19 急性呼吸窘迫综合征 (ARDS) 死亡率明显高于其他来源 ARDS 的原因。在高血压、糖尿病或癌症等慢性非传染性疾病中，味觉和/或嗅觉受损一直有报道。这可能表明弥漫性化学感觉衰竭，可能会使这些患者的预后恶化。在普通生活条件下，一个或少数化学感觉系统的失能对生存几乎没有影响，但在代谢失衡或 COVID-19 肺炎等压力下，多个化学感觉系统的失能可能会在疾病过程中导致严重后果。
