Inspiration and inflammation in the breathing brainstem

Neonatal breathing is highly vulnerable to disturbances, and conditions such as respiratory distress syndrome, apnea, and Sudden Unexpected Postnatal Collapse (SUPC). These conditions can result in severe complications or death. The brainstem, particularly the preBötzinger Complex (preBötC), is crucial in generating the rhythmic breathing patterns necessary for survival. This region adapts respiratory rhythms to metabolic demands and integrates signals from both neurons and astrocytes. Understanding how external factors, such as inflammation, affect these circuits is vital for developing therapeutic strategies for neonates.

Study I aimed to investigate the effects of prostaglandin E2 (PGE2) on the respiratory rhythm within the preBotC. The study demonstrated that PGE2 exerts a biphasic dose-dependent effect. Increasing the burst period at low concentrations (1-10 nM) and decreasing it at high concentrations (1 uM). These changes were receptor-specific, with EP2 and EP3 receptors playing distinct roles in modulating the inspiratory rhythm. This highlights the importance of PGE2 in respiratory regulation and suggest that EP2 and EP3 receptors may serve as potential therapeutic targets.

Study II focused on developing astroCaST, a novel toolkit designed to analyze astrocytic calcium dynamics at scale. The toolkit enables efficient detection and clustering of calcium events in large datasets, surpassing existing tools in both memory usage and processing speed. AstroCaST facilitates the study of astrocyte contributions to respiratory control by identifying and categorizing stereotypical astrocytic calcium events. This tool has proven essential in large- scale studies of astrocytic activity, as demonstrated in study III.

Study III applied astroCaST to investigate how astrocytic calcium dynamics contribute to respiratory rhythm generation in the preBötC, both at rest and under hypercapnic conditions. Astrocytic calcium events can predict respiratory burst onset with reasonable accuracy and distinguish between different respiratory patterns, such as eupneic bursts and sighs. Moreover, these calcium dynamics were found to be sensitive to changes in carbon dioxide levels and pH, showing distinct responses under different hypercapnic conditions.

In summary, this thesis explores the role of both neuronal and astrocytic activity in neonatal respiratory control, focusing on the preBötC. Study I demonstrates the biphasic effects of PGE2 on respiratory rhythms, highlighting its therapeutic potential. Study II introduces astroCaST, a robust tool for analyzing astrocytic calcium signaling. Study III applies the toolkit to reveal that astrocytic calcium events depend on types of respiratory bursts and vary depending on CO2 and pH. Together, these studies provide new insights into how inflammation and astrocytic activity modulate respiratory rhythms, offering methodological advancements and potential therapeutic approaches for improving neonatal respiratory outcomes.

List of scientific papers

I. Reising JP, Phillips WS, Ramadan N, Herlenius E. Prostaglandin E2 exerts biphasic dose response on the PreBötzinger complex respiratory-related rhythm. Frontiers in neural circuits. 2022 May 20;16:826497.
https://doi.org/10.3389/fncir.2022.826497

II. Reising JP, Gonzalez-Sanchez AC, Samara A, Herlenius E. Astrocytic Calcium Signaling Toolkit (astroCaST): efficient analysis of dynamic astrocytic calcium events. Frontiers in Cellular Neuroscience. 2024 Jun 10;18:1408607.
https://doi.org/10.3389/fncel.2024.1408607

III. Reising JP, Phillips WS, Samara A, Herlenius E. Glue or Glitch? Resolving astrocytic calcium dynamics in inspiratory rhythm generation. [Manuscript]