Calcium/calmodulin-dependent kinase II mediates critical components of the hypoxic ventilatory response within the nucleus of the solitary tract in adult rats

T cell infiltration into the brain triggers pulmonary dysfunction in murine Cryptococcus-associated IRIS

Cryptococcus-associated immune reconstitution inflammatory syndrome (C-IRIS) is a condition frequently occurring in immunocompromised patients receiving antiretroviral therapy. C-IRIS patients exhibit many critical symptoms, including pulmonary distress, potentially complicating the progression and recovery from this condition. Here, utilizing our previously established mouse model of unmasking C-IRIS (CnH99 preinfection and adoptive transfer of CD4⁺ T cells), we demonstrated that pulmonary dysfunction associated with the C-IRIS condition in mice could be attributed to the infiltration of CD4⁺ T cells into the brain via the CCL8-CCR5 axis, which triggers the nucleus tractus solitarius (NTS) neuronal damage and neuronal disconnection via upregulated ephrin B3 and semaphorin 6B in CD4⁺ T cells. Our findings provide unique insight into the mechanism behind pulmonary dysfunction in C-IRIS and nominate potential therapeutic targets for treatment.

Protein kinase C activity in the nucleus tractus solitarii is critically involved in the acute hypoxic ventilatory response, but is not required for intermittent hypoxia-induced phrenic long-term facilitation in adult rats

Protein kinase C (PKC) is a broadly expressed and critically important signalling protein with a wide range of functional roles, including central components of respiratory control. For example, systemic and targeted administration of PKC inhibitors within the nucleus of the solitary tract (nTS) markedly attenuates peak hypoxic ventilatory responses (HVR). Protein kinase C activation in phrenic motor nucleus has also been implicated in some forms of acute respiratory plasticity, such as phrenic long-term facilitation (pLTF), a persistent enhancement of phrenic motor output following acute intermittent hypoxia. To further examine the role of PKC within the nTS, the selective PKC antagonist bisindolylmaleimide I (BIM I) was microinjected in the area corresponding to the nTS via bilateral osmotic pumps in normoxic adult male Sprague-Dawley rats; control animals received bisindolylmaleimide V (BIM V, inactive analogue). In one series of experiments, hypoxic challenges (fractional inspired ) were conducted in unrestrained animals (n = 8 per group). No differences in baseline ventilation emerged; however, peak HVR was attenuated following BIM I (P < 0.01), primarily owing to reductions in respiratory frequency increases (P < 0.01). In a second series of experiments, integrated phrenic nerve activity was recorded in anaesthetized, vagotomized, paralysed and ventilated rats exposed to three 5 min hypoxic episodes separated by 5 min hyperoxia . During baseline conditions, no differences emerged in phrenic nerve output; however, phrenic nerve output measured during the initial hypoxic exposure was significantly attenuated in BIM I-treated rats (P < 0.01). In contrast, both groups of animals displayed significant pLTF (BIM I versus BIM V; n.s.). Thus, we conclude that PKC activation within the nTS is critically involved in the central response to acute hypoxia, but does not appear to play a role in either eliciting or maintaining pLTF.

Chronic alcohol exposure alters transcription broadly in a key integrative brain nucleus for homeostasis: the nucleus tractus solitarius

Chronic exposure to alcohol modifies physiological processes in the brain, and the severe symptoms resulting from sudden removal of alcohol from the diet indicate that these modifications are functionally important. We investigated the gene expression patterns in response to chronic alcohol exposure (21–28 wk) in the rat nucleus tractus solitarius (NTS), a brain nucleus with a key integrative role in homeostasis and cardiorespiratory function. Using methods and an experimental design optimized for detecting transcriptional changes less than twofold, we found 575 differentially expressed genes. We tested these genes for significant associations with physiological functions and signaling pathways using Gene Ontology terms and the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, respectively. Chronic alcohol exposure resulted in significant NTS gene regulation related to the general processes of synaptic transmission, intracellular signaling, and cation transport as well as specific neuronal functions including plasticity and seizure behavior that could be related to alcohol withdrawal symptoms. The differentially expressed genes were also significantly enriched for enzymes of lipid metabolism, glucose metabolism, oxidative phosphorylation, MAP kinase signaling, and calcium signaling pathways from KEGG. Intriguingly, many of the genes we found to be differentially expressed in the NTS are known to be involved in alcohol-induced oxidative stress and/or cell death. The study provides evidence of very extensive alterations of physiological gene expression in the NTS in the adapted state to chronic alcohol exposure.