Abnormal respiration under hyperoxia in TASK-1/3 potassium channel double knockout mice

KCNK3 channel is important for the ventilatory response to hypoxia in rats

To clarify the contribution of KCNK3/TASK-1 channel chemoreflex in response to hypoxia and hypercapnia, we used a unique Kcnk3-deficient rat. We assessed ventilatory variables using plethysmography in Kcnk3-deficient and wild-type rats at rest in response to hypoxia (10% O2) and hypercapnia (4% CO2). Immunostaining for C-Fos, a marker of neuronal activity, was performed to identify the regions of the respiratory neuronal network involved in the observed response.Under basal conditions, we observed increased minute ventilation in Kcnk3-deficient rats, which was associated with increased c-Fos positive cells in the ventrolateral region of the medulla oblongata. Kcnk3-deficient rats show an increase in ventilatory response to hypoxia without changes in response to hypercapnia. In Kcnk3-deficient rats, linked to an increased hypoxia response, we observed a greater increase in c-Fos-positive cells in the first central relay of peripheral chemoreceptors and Raphe Obscurus. This study reports that KCNK3/TASK-1 deficiency in rats induces an inadequate peripheral chemoreflex, alternating respiratory rhythmogenesis, and hypoxic chemoreflex.

Autonomic dysfunction in epilepsy mouse models with implications for SUDEP research

Epilepsy has a high prevalence and can severely impair quality of life and increase the risk of premature death. Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in drug-resistant epilepsy and most often results from respiratory and cardiac impairments due to brainstem dysfunction. Epileptic activity can spread widely, influencing neuronal activity in regions outside the epileptic network. The brainstem controls cardiorespiratory activity and arousal and reciprocally connects to cortical, diencephalic, and spinal cord areas. Epileptic activity can propagate trans-synaptically or via spreading depression (SD) to alter brainstem functions and cause cardiorespiratory dysfunction. The mechanisms by which seizures propagate to or otherwise impair brainstem function and trigger the cascading effects that cause SUDEP are poorly understood. We review insights from mouse models combined with new techniques to understand the pathophysiology of epilepsy and SUDEP. These techniques include in vivo, ex vivo, invasive and non-invasive methods in anesthetized and awake mice. Optogenetics combined with electrophysiological and optical manipulation and recording methods offer unique opportunities to study neuronal mechanisms under normal conditions, during and after non-fatal seizures, and in SUDEP. These combined approaches can advance our understanding of brainstem pathophysiology associated with seizures and SUDEP and may suggest strategies to prevent SUDEP.

Genetic variants of rs1275988 and rs2586886 in TWIK-related acid-sensitive K+ channel-1 gene may be potential risk factors for obese patients with obstructive sleep apnea

Background:

The pathogenesis of obstructive sleep apnea (OSA) remains not fully understood. This study aimed to explore the mechanism of OSA by assessing the association between the human tandem of P domains in a weak inwardly rectifying K⁺ channel (TWIK)-related acid-sensitive K⁺ channel-1 (TASK-1) gene and OSA.

Methods:

A total of 164 patients with severe OSA and 171 patients without OSA were recruited from the Center for Hypertension of People's Hospital of Xinjiang Uygur Autonomous Region (China) from April to December in 2016. Two single nucleotide polymorphisms (rs1275988 and rs2586886) in the TASK-1 gene were selected and genotyped using a kompetitive allele specific polymerase chain reaction genotyping system. Clinical-pathological characteristics and genotype data were compared between the severe and non-OSA groups to explore the association between TASK-1 gene polymorphism and severe OSA.

Results:

There were no significant differences in genotype distribution, allele frequency, and the recessive and dominant model of the two selected single nucleotide polymorphisms (rs1275988 and rs2586886) between the severe and non-OSA groups in the total population (P > 0.05). However, for patients with a body mass index (BMI) ≥28 kg/m², the distribution of genotypes and alleles, and the recessive model (GG + GA vs. AA) exhibited significant differences between the severe and non-OSA group (for genotypes: P = 0.014 and P = 0.026; for alleles: P = 0.006 and P = 0.011; for the recessive model: P = 0.005 and P = 0.009, respectively). The simple logistic regression analysis revealed that the GG genotype was a risk factor for OSA. The odds ratio (OR) and 95% confidence intervals (CI) were 4.902 (1.582–15.186, P = 0.006) for rs1275988 and 4.420 (1.422–13.734, P = 0.010) for rs2586886, respectively. In multivariate logistic regression analysis, the combination of GG genotypes of rs1275988 with BMI ≥28 kg/m² increased the risk of severe OSA (OR = 8.916, 95% CI 4.506–17.645, P < 0.001).

Conclusion:

Both the GG genotype of rs1275988 and GG genotype of rs2586886 in the TASK-1 gene may play as potential risk factors in obese patients with OSA.

TASK1 and TASK3 Are Coexpressed With ASIC1 in the Ventrolateral Medulla and Contribute to Central Chemoreception in Rats

The ventrolateral medulla (VLM), including the lateral paragigantocellular nucleus (LPGi) and rostral VLM (RVLM), is commonly considered to be a chemosensitive region. However, the specific mechanism of chemoreception in the VLM remains elusive. Acid-sensing ion channels (ASICs), a family of voltage-independent proton-gated cation channels, can be activated by an external pH decrease to cause Na⁺ entry and induce neuronal excitability. TWIK-related acid-sensitive potassium channels (TASKs) are members of another group of pH-sensitive channels; in contrast to AISICs, they can be stimulated by pH increases and are inhibited by pH decreases in the physiological range. Our previous study demonstrated that ASICs take part in chemoreception. The aims of this study are to explore whether TASKs participate in the acid sensitivity of neurons in the VLM, thereby cooperating with ASICs. Our research demonstrated that TASKs, including TASK1 and TASK3, are colocalized with ASIC1 in VLM neurons. Blocking TASKs by microinjection of the non-selective TASK antagonist bupivacaine (BUP), specific TASK1 antagonist anandamide (AEA) or specific TASK3 antagonist ruthenium red (RR) into the VLM increased the integrated phrenic nerve discharge (iPND), shortened the inspiratory time (Ti) and enhanced the respiratory drive (iPND/Ti). In addition, microinjection of artificial cerebrospinal fluid (ACSF) at a pH of 7.0 or 6.5 prolonged Ti, increased iPND and enhanced respiratory drive, which were inhibited by the ASIC antagonist amiloride (AMI). By contrast, microinjection of alkaline ACSF decreased iPND and respiratory drive, which were inhibited by AEA. Taken together, our data suggest that TASK1 and TASK3 are coexpressed with ASIC1 in the VLM. Moreover, TASK1 and TASK3 contribute to the central regulation of breathing by coordinating with each other to perceive local pH changes; these results indicate a novel chemosensitive mechanism of the VLM.