The Beneficial Effects of Krypton Inhalation Following Traumatic Brain Injury in Rats

Traumatic brain injury (TBI) remains one of the leading causes of disability, and current approaches to neuroprotection have limited efficacy. The inert gas krypton is considered a promising neuroprotective agent; however, data on its effects in TBI and on components of the neurovascular unit (NVU) are limited. Objective. To evaluate the neuroprotective potential of krypton in rats with traumatic brain injury (TBI) in vivo and in NVU cell cultures subjected to oxygen-glucose deprivation (OGD) in vitro . Materials and Methods. The study included 48 Wistar rats divided into 3 groups: SO (sham operated), TBI (N₂/O₂ 70/30 %), and TBI + iKr (Kr/O₂ 70/30 %). A model of controlled open brain contusion injury was used. On day 14, we assessed neurological deficits (limb placing test, LPT), the extent of brain injury (T2-weighted MRI slices), morphological changes (hematoxylin-eosin staining), and the expression of GFAP and Caspase-3 (fluorescent immunohistochemistry, IHC). IL-1β, IL-6, and TNF-α mRNA levels in the injury zone were determined by PCR. In vitro studies investigated the effect of krypton preconditioning (Kr/O₂ 79/21 %, 24 h) on the survival of neuronal (SH-SY5Y), glial (C6), and vascular endothelial (Ea.Hy926) cells during OGD (4–6 h). Results. A significant neurological deficit of 2.5 (2; 5.25) scores was determined by the TBI modeling accompanied by a large volume of brain damage of 33 (28; 39) mm³. Krypton inhalation led to a reduction in the lesion volume to 18 (15; 26) mm³ and accelerated the recovery of sensorimotor functions: starting on day 7, the indicators in the TBI + iKr group were statistically significantly better than in the TBI group, and by day 14, they approached the values of the SO (control) group. In the TBI + iKr group, IL-1β and TNF-α levels in the affected hemisphere were nearly 50% lower than in the TBI group, while remaining higher than in the SO group; changes in IL-6 levels were insignificant. Histologically, less significant cerebral edema, spongiosis, and neuronal degeneration were observed in the TBI + iKr group. Immunohistochemical analysis revealed a trend toward more pronounced reactive gliosis (GFAP) with no differences in Caspase-3. In vitro , krypton preconditioning under OGD conditions did not improve the survival of neuronal, glial, and endothelial cells. Conclusion. Krypton exerted significant neuroprotective effect in experimental TBI in rats, reducing neurological deficits, the extent of structural damage, and the severity of the inflammatory response. The absence of a protective effect in NVU cellular models underscores the essential role of systemic and intercellular interactions in the neuroprotective action of krypton and warrants further research into its mechanisms of action and dosing optimization.