Reduced acute neuroinflammation and improved functional recovery after traumatic brain injury by α-linolenic acid supplementation in mice.
BACKGROUND
Adequate consumption of polyunsaturated fatty acids (PUFA) is vital for normal development and functioning of the central nervous system. The long-chain n-3 PUFAs docosahexaenoic acid (DHA) and eicosapentaenoic acid are anti-inflammatory and neuroprotective in the models of central nervous system injury including traumatic brain injury (TBI). In the present study, we tested whether a higher brain DHA status in a mouse model on an adequate dietary α-linolenic acid (ALA) leads to reduced neuroinflammation and improved spontaneous recovery after TBI in comparison to a moderately lowered brain DHA status that can occur in humans.


METHODS
Mice reared on diets with differing ALA content were injured by a single cortical contusion impact. Change in the expression of inflammatory cytokines was measured, and cellular changes occurring after injury were analyzed by immunostaining for macrophage/microglia and astrocytes. Behavioral studies included rotarod and beam walk tests and contextual fear conditioning.


RESULTS
Marginal supply (0.04 %) of ALA as the sole dietary source of n-3 PUFA from early gestation produced reduction of brain DHA by 35 % in adult offspring mice in comparison to the mice on adequate ALA diet (3.1 %). The DHA-depleted group showed significantly increased TBI-induced expression of pro-inflammatory cytokines TNF-α, IL-1β, and IL-6 in the brain as well as slower functional recovery from motor deficits compared to the adequate ALA group. Despite the reduction of pro-inflammatory cytokine expression, adequate ALA diet did not significantly alter either microglia/macrophage density around the contusion site or the relative M1/M2 phenotype. However, the glial fibrillary acidic protein immunoreactivity was reduced in the injured cerebral cortex of the mice on adequate ALA diet, indicating that astrocyte activation may have contributed to the observed differences in cellular and behavioral responses to TBI.


CONCLUSIONS
Increasing the brain DHA level even from a moderately DHA-depleted state can reduce neuroinflammation and improve functional recovery after TBI, suggesting possible improvement of functional outcome by increasing dietary n-3 PUFA in human TBI.
Laboratory of Molecular Signaling, National Institute of Alcohol Abuse and Alcoholism, National Institutes of Health, 5625 Fishers Lane, Rm. 3N-07, Bethesda, MD, 20892-9410, USA.
Abhishek
A
Desai
Laboratory of Molecular Signaling, National Institute of Alcohol Abuse and Alcoholism, National Institutes of Health, 5625 Fishers Lane, Rm. 3N-07, Bethesda, MD, 20892-9410, USA.
Taeyeop
T
Park
Laboratory of Molecular Signaling, National Institute of Alcohol Abuse and Alcoholism, National Institutes of Health, 5625 Fishers Lane, Rm. 3N-07, Bethesda, MD, 20892-9410, USA.
Jaquel
J
Barnes
Laboratory of Molecular Signaling, National Institute of Alcohol Abuse and Alcoholism, National Institutes of Health, 5625 Fishers Lane, Rm. 3N-07, Bethesda, MD, 20892-9410, USA.
Karl
K
Kevala
Laboratory of Molecular Signaling, National Institute of Alcohol Abuse and Alcoholism, National Institutes of Health, 5625 Fishers Lane, Rm. 3N-07, Bethesda, MD, 20892-9410, USA.
Huazhen
H
Chen
Laboratory of Molecular Signaling, National Institute of Alcohol Abuse and Alcoholism, National Institutes of Health, 5625 Fishers Lane, Rm. 3N-07, Bethesda, MD, 20892-9410, USA. hykim@nih.gov.
Hee-Yong
http://orcid.org/0000-0002-5546-8052
HY
Kim
Alpha-linolenic acid (ALA); Diet; Docosahexaenoic acid (DHA); Inflammation; Nutrition; Polyunsaturated fatty acids (PUFA); Traumatic brain injury (TBI)
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