Inhibition of Protein Kinases AKT and ERK1/2 Reduce the Carotid Body Chemoreceptor Response to Hypoxia in Adult Rats

Abstract

The carotid body is the main mammalian oxygen-sensing organ regulating ventilation. Despite the carotid body is subjected of extensive anatomical and functional studies, little is yet known about the molecular pathways signaling the neurotransmission and neuromodulation of the chemoreflex activity. As kinases are molecules widely involved in motioning a broad number of neural processes, here we hypothesized that pathways of protein kinase B (AKT) and extracellular signal-regulated kinases ½ (ERK1/2) are implicated in the carotid body response to hypoxia. This hypothesis was tested using the in-vitro carotid body/carotid sinus nerve preparation ("en bloc") from Sprague Dawley adult rats. Preparations were incubated for 60 min in tyrode perfusion solution (control) or containing 1 μM of LY294002 (AKT inhibitor), or 1 μM of UO-126 (ERK1/2 inhibitor). The carotid sinus nerve chemoreceptor discharge rate was recorded under baseline (perfusion solution bubbled with 5 % CO(2) balanced in O(2)) and hypoxic (perfusion solution bubbled with 5 % CO(2) balanced in N(2)) conditions. Compared to control, both inhibitors significantly decreased the normoxic and hypoxic carotid body chemoreceptor activity. LY294002- reduced carotid sinus nerve discharge rate in hypoxia by about 20 %, while UO-126 reduces the hypoxic response by 45 %. We concluded that both AKT and ERK1/2 pathways are crucial for the carotid body intracellular signaling process in response to hypoxia.

Neonatal Maternal Separation Augments Carotid Body Response to Hypoxia in Adult Males but Not Female Rats

“…The carotid body's responses to hypoxia and hypercapnia have been studied extensively in male rats; however, the diversity of the approaches used ( ex vivo vs. in situ ), recording technique (whole nerve vs. single fiber), data normalization, developmental stage, and experimental condition (PO 2 level at rest, intensity of the O 2 /CO 2 stimulus) makes it difficult to make proper comparison with other studies. However, the level of activity and responses reported in males during hypoxia and hypercapnia are comparable with those reported by our group and other laboratories (Cummings and Wilson, 2005 ; Prabhakar et al, 2007 ; Iturri et al, 2015 ). Data from females are difficult to compare since, to the best of our knowledge, investigations of carotid body function have been performed in adult female rats.…”

“…Carotid sinus nerve activity (CSN) was assessed by measuring the number of impulses above threshold per seconds on a second-by-second basis. Initially, hyperoxic activity was calculated for the baseline and recovery periods by averaging values over 150 s. The plateau of the response was obtained by averaging the activity over a 250 s period under hypoxic and hypercapnic conditions according to our previous protocol (Iturri et al, 2015 ). Since the hypoxic response measured in NMS females was significantly lower, these periods were extended to 200 and 300 s (baseline and hypoxic/hypercapnic stimulation, respectively) to ensure that differences were not due delays in the response.…”

Erythropoietin Produces a Dual Effect on Carotid Body Chemoreception in Male Rats

“…The CSN activity was assessed by measuring the number of impulses above threshold per seconds on a second-by-second basis. Initially, baseline activity was calculated for the baseline and recovery periods by averaging values over 150 s. The plateau of the response was obtained by averaging the activity over a 500–700 s period under hypoxic and hypercapnic conditions according to our previous protocol ( Iturri et al, 2015 ).…”

Erythropoietin Produces a Dual Effect on Carotid Body Chemoreception in Male Rats

“…Standard methods were used to record action potentials from the carotid sinus nerve ex vivo (Iturri et al, 2015;Soliz et al, 2016). Briefly, the preparation was deposited in the recording chamber (volume 5.4 ml) and a catheter was placed between the infusion solution inlet and the common carotid artery (Figures 1A,D).…”

“…The CSN activity was assessed by measuring the number of impulses above threshold per seconds on a second-by-second basis. Initially, baseline activity was calculated for the baseline and recovery periods by averaging values over 150 s. The plateau of the response was obtained by averaging the activity over a 500-700 s period under hypoxic and hypercapnic conditions according to our previous protocol (Iturri et al, 2015). All statistical analyses were performed using GraphPad Prism version 9.1 for Windows, GraphPad Software, San Diego, California United States, www.graphpad.com.…”