During repeated hypoxic episodes, the body activates protective mechanisms designed to restore oxygen delivery. However, chronic activation of these pathways can become harmful.
A key regulator of this response is the carotid body, a peripheral chemoreceptor responsible for sensing changes in blood oxygen levels. In animal models of CIH, the carotid body becomes hypersensitive, producing an exaggerated response to acute hypoxia. This heightened activity chronically stimulates the sympathetic nervous system, increasing heart rate, blood pressure, and cardiovascular stress.
Previous rodent studies have demonstrated that removing the carotid body prevents CIH-induced sympathetic activation and hypertension, highlighting its central role in the cardiovascular complications associated with OSA.
To better understand the molecular pathways responsible for carotid body activation, Dr. Peng’s research group at the University of Chicago investigated the role of the Olfr78 receptor, an olfactory receptor expressed within the murine carotid body.
Earlier work had shown that deleting the Olfr78 gene impairs the carotid body’s response to acute hypoxia. The researchers further explored this pathway using mice lacking heme oxygenase-2 (HO-2), an enzyme involved in oxygen sensing. Because HO-2 knockout mice naturally experience spontaneous sleep apneas, they provide an ideal model for studying OSA-related respiratory dysfunction and CIH-induced hypertension.
To evaluate respiratory function, researchers used Whole-Body Plethysmography, a non-invasive technique that continuously measures breathing patterns and detects spontaneous apneic events in conscious mice.
Following exposure to Chronic Intermittent Hypoxia, several important findings emerged:
These findings demonstrate that loss of Olfr78 protects against many of the physiological changes associated with Chronic Intermittent Hypoxia.
This study provides compelling evidence that the Olfr78 receptor contributes to carotid body-dependent sympathetic activation and the development of hypertension in multiple mouse models of Chronic Intermittent Hypoxia.
By identifying the molecular pathways that connect intermittent hypoxia with elevated blood pressure, this research advances our understanding of the cardiovascular consequences of Obstructive Sleep Apnea and highlights potential therapeutic targets for future treatment strategies.
Additionally, the study demonstrates the value of Whole-Body Plethysmography for quantifying breathing instability and apneic events in preclinical models, enabling researchers to better investigate the respiratory and cardiovascular mechanisms underlying sleep apnea.
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