Early treatment with naproxen alters hippocampal metabolites in the TgF344-AD rat model of Alzheimer's disease.

Abstract

Alzheimer's disease (AD) is characterized by the appearance of brain pathology decades prior to clinical symptoms. The pre-symptomatic phase of AD provides opportunity for early detection and intervention. One early intervention that has been proposed is the use of non-steroidal anti-inflammatory drugs (NSAIDs), such as naproxen. However, evidence suggests that effects of naproxen intervention differ with stage of the disease, and the optimal intervention time is not clear. Accordingly, in this study, we investigated the impact of the timing of naproxen treatment in a rat model of AD. We used the TgF344-AD rat model of AD which develops characteristic pathological features of human AD, including abundant amyloid plaque pathology, astrogliosis, and microgliosis by 6 months of age, and neurofibrillary tangles and neuronal loss by 16 months of age. We examined the effects of naproxen treatment beginning at 1, 4, and 10 months of age in transgenic (Tg) animals and their wild-type (WT) littermates. We used longitudinal in vivo magnetic resonance spectroscopy (MRS) to study the impact of naproxen treatment on hippocampus neurochemistry. Previous studies have used MRS to non-invasively characterize the trajectory of altered hippocampal neurochemistry across the lifespan in the TgF344-AD rat model. In the current study, we employed MRS at 4, 10, and 16 months, i.e. prior to or after the appearance of amyloidosis and gliosis (6 months) and tau pathology (16 months), respectively, in Tg animals. Naproxen treatment altered neurochemistry in Tg animals only if administered beginning at 1 or 4 months of age, mitigating an otherwise observed increase in total choline and decrease in taurine. A more subtle effect was observed on the otherwise-expected increase in myo-inositol. These results highlight the possibility that earlier naproxen intervention could have distinct neurochemical effects compared to delayed treatment, though mechanistic implications remain to be clarified. Moreover, these findings support the use of MRS as a useful non-invasive method of monitoring treatment-related changes in neurochemistry in transgenic animal models.