The balance between efficient anti-inflammatory treatment and neuronal regeneration in the olfactory epithelium.

The sense of smell is important for human quality of life. This sophisticated sensorial system relies on the detection of odorant molecules that engage receptors expressed in the cilia of dedicated neurons that constitute the olfactory epithelium (OE). Importantly, the OE is a highly active site of adult neurogenesis where short-lived neurons are efficiently replenished, even after massive neuronal cell loss. It is suggested that the degree of olfactory function recovery after OE injury may depend on the nature of the lesion (traumatic, chemical, infectious or inflammatory), as well on the velocity of cellular regeneration. Topical steroidal anti-inflammatory drugs, such as glucocorticoids, are routinely prescribed for treating upper airway inflammatory conditions, such as chronic rhinosinusitis. While the therapeutic strategy aims to minimize the inflammatory damage and dysfunction to nasal air conduction, new evidences raise concerns if such drugs may impair neuronal regeneration in the OE. In consequence, new directions are necessary in terms of drug development or prescription, in order to preserve olfactory function through lifelong repeated episodes of chronic inflammation in the upper respiratory tract. Here we discuss mechanisms involved in glucocorticoid deleterious effects to OE regeneration and possible therapeutic alternatives considering relevant side effects.