¹University of Florida College of Medicine, Anesthesiology, Gainesville, United States, ²McKnight Brain Institute, University of Florida College of Medicine, Psychiatry, Gainesville, United States, ³McKnight Brain Institute, University of Florida College of Medicine, Anesthesiology and Neuroscience, Gainesville, United States

Background: Long-term consequences of traumatic brain injury (TBI) include dysregulated stress and inflammatory signaling and neurocognitive decline. Epidemiological evidence indicates increased psychiatric vulnerability in the offspring of parents with TBI, with greater abnormalities in sons. The mechanisms initiating these abnormalities, whether they arise in offspring through altered social interactions with TBI-affected parents or are transmitted via biological pathways before birth, and strategies for prevention remain unclear.

Aims & Objectives: We investigated the roles of stress and inflammatory signaling in initiating intergenerational outcomes following maternal preconception TBI, the influence of pre- and postnatal maternal factors on offspring development, and the potential of pharmacological modulation of these mechanisms to prevent such outcomes.

Method: Postnatal day 60 (P60) Sprague Dawley female rats underwent moderate TBI via midline fluid percussion injury (F0F_T group). A subset of F0F_T received the NKCC1 inhibitor bumetanide prior to TBI induction (F0F_BT), while F0F_T and control females (F0F_C) received saline. At P90, these groups were bred to produce offspring (F1). To assess the influence of postnatal mother-offspring interactions, half of the offspring from F0F_C dams were reared from birth by F0F_T dams, while half of the offspring from F0F_T dams were reared by F0F_C dams. Both generations were sequentially evaluated in behavioral tests beginning at P130 (F0) or P50 (F1), followed by mechanistic studies. Vaginal (F0) and gut microbiomes (F0 and F1) were profiled using 16S rRNA gene sequencing.

Results: F0F_T dams exhibited persistently heightened corticosterone responses to stress, elevated systemic inflammatory markers, mild changes in gut and vaginal microbiomes, and unaltered weight, behavior, and caregiving toward offspring. Their male offspring showed reduced birth and weaning weights, decreased hippocampal glucocorticoid receptor mRNA transcripts, exaggerated corticosterone responses to stress, elevated inflammatory markers, gut dysbiosis, reduced sociability, increased anxiety, and impaired spatial memory, while female offspring displayed similar changes in weight and anxiety but were otherwise unaffected. Bumetanide normalized maternal stress and inflammatory signaling and protected offspring across all measures. In fostered offspring, F0F_C mothers improved weaning weight and normalized inflammatory markers but did not reduce anxiety, whereas F0F_T mothers induced anxiety without affecting weight, inflammatory markers, or gut microbiome. Other parameters in fostered offspring shifted toward those of the fostering dams’ biological offspring, with no significant differences compared with control or F0F_T offspring reared by biological dams.

Discussion & Conclusions: Maternal preconception moderate TBI induces persistent stress and inflammatory dysregulation in dams, as well as sex-dependent gut microbiota and neurobehavioral abnormalities in offspring through both prenatal and postnatal pathways. The absence of growth deficits in foster pups and the lack of overt changes in F0F_T caregiving behavior suggest that rather than “physical” factors (e.g., nursing, licking), “social” interactions between mother and offspring, likely involving dysregulated stress and inflammatory signaling, were major contributors to postnatal maternal influences. Bumetanide prevented all abnormalities, implicating maternal stress and inflammation as key drivers of both pre- and postnatal effects and identifying NKCC1 as a potential therapeutic target.
Funding: NIH (R01HD107722, R56HD102898 to A.E.M.; IHAF to Z.A.K. and L-S.J.).