RESUMEN
Background: Pulmonary arteriovenous malformations (PAVMs) universally develop in patients with single ventricle congenital heart disease (CHD). Single ventricle PAVMs have been recognized for over 50 years, yet they are poorly understood, and we lack any medical therapies. To improve our understanding of single ventricle PAVM initiation and progression, we developed a surgical rat model of Glenn circulation and characterized PAVM physiology over multiple time points. Methods: Using adult rats, we performed a left thoracotomy and end-to-end anastomosis of the left superior vena cava to the left pulmonary artery (unilateral Glenn), or sham surgical control. To assess for PAVM physiology in the left lung, we quantified intrapulmonary shunting using two independent methods (bubble echocardiography and fluorescent microsphere injection) at 2 weeks, 2 months, and 6 months. Additionally, we performed arterial blood gas measurements to assess oxygenation and plethysmography to assess ventilation. Results: We identified pathologic intrapulmonary shunting by bubble echocardiography as early as 2 weeks post-Glenn surgery, and shunting continued chronically at 2- and 6-months post-Glenn. Shunting also progressed over time, demonstrated by increased shunting of 10µm microspheres at 6 months. Shunting was accompanied by mildly decreased arterial oxygenation, but there were no differences in ventilation as quantified by plethysmography. Conclusions: Our surgical animal model of unilateral Glenn circulation re-creates the clinical condition of single ventricle PAVMs with early and progressive intrapulmonary shunting. This model is poised to characterize single ventricle PAVM pathophysiology and lead to mechanistic and therapeutic discovery.
RESUMEN
Patients with epilepsy face heightened risk of post-ictal cardiorespiratory suppression and sudden unexpected death in epilepsy (SUDEP). Studies have shown that neuroinflammation, mediated by the activation of microglia and astrocytes, may be a cause or consequence of seizure disorders. Kcnj16 (Kir5.1) knockout rats (SS kcnj16-/- ) are susceptible to repeated audiogenic seizures and recapitulate features of human SUDEP, including post-ictal ventilatory suppression, which worsens with repeated seizures and seizure-induced mortality. In this study, we tested the hypothesis that repeated seizures cause neuroinflammation within key brainstem regions that contribute to the control of breathing. Audiogenic seizures were elicited once/day for up to 10 days in groups of adult male SS kcnj16-/- rats, from which frozen brainstem biopsies of the pre-Bötzinger complex/nucleus ambiguus (preBötC/NA), Bötzinger complex (BötC), and raphe magnus (RMg) regions were subjected to a cytokine array. Several cytokines/chemokines, including IL-1α and IL-1ß, were increased selectively in preBötC/NA after 3 or 5 days of seizures with fewer changes in other regions tested. In additional groups of male SS kcnj16-/- rats that underwent repeated seizures, we quantified microglial (IBA-1+) cell counts and morphology, specifically within the preBötC/NA region, and showed increased microglial cell counts, area, and volume consistent with microglial activation. To further test the role of inflammation in physiological responses to seizures and seizure-related mortality, additional groups of SS kcnj16-/- rats were treated with anakinra (IL-1R antagonist), ketoprofen (non-selective COX inhibitor), or saline for 3 days before and up to 10 days of seizures (1/day), and breathing was measured before, during, and after each seizure. Remarkably, IL-1R antagonism mitigated changes in post-ictal ventilatory suppression on days 7-10 but failed to prevent seizure-related mortality, whereas ketoprofen treatment exacerbated post-ictal ventilatory suppression compared to other treatment groups but prevented seizure-related mortality. These data demonstrate neuroinflammation and microglial activation within the key brainstem region of respiratory control following repeated seizures, which may functionally but differentially contribute to the pathophysiological consequences of repeated seizures.