Organic Cation Transporters are Involved in Fluoxetine Transport Across the Blood-Brain Barrier in Vivo and in Vitro

Xiaoyaosan promotes neurotransmitter transmission and alleviates CUMS-induced depression by regulating the expression of Oct1 and Oct3 in astrocytes of the prefrontal cortex

ETHNOPHARMACOLOGICAL RELEVANCE

Xiaoyaosan (XYS) is a traditional prescription for the treatment of liver depression and qi stagnation, and pharmacological studies have shown that XYS has great potential to reverse depression. However, anti-depression targets and the mechanism of XYS are still not entirely clear.

AIM OF THE STUDY

The present study aims to explore and verify the anti-depression mechanism of XYS.

MATERIALS AND METHODS

The antidepressant effect of XYS was assessed in rats with depression induced by chronic unpredictable mild stimulation (CUMS). The levels of 5-hydroxytryptamine (5-HT), dopamine (DA), and norepinephrine (NE) in different brain regions were measured using ELISA. The expression of organic cation transporters (Octs) were detected by western blot and immunohistochemical techniques. Then, Decynium-22 (D22), an Octs inhibitor, was injected into the prefrontal cortex (PFC) to verify the correlation between Octs and depression-like behavior. Then, the effects of XYS on the behavior, neurotransmitter concentration, and Octs expression in D22-induced rats were examined. Finally, primary astrocytes were used to verify the mechanism of XYS exerting anti-depressant activity by regulating Octs.

RESULTS

The result showed that XYS had a significant positive impact on the behavior of depression rats induced by CUMS. XYS also improved the secretion of 5-HT, DA, and NE in the PFC, as well as the promotion of Oct1, Oct2, and Oct3 expression in the PFC. These results suggest that XYS has the potential to alleviate depression by enhancing the secretion of neurotransmitters. This may be related to XYS regulation of Oct's expression. When the expression of Octs was inhibited in the PFC, rats exhibited behavior similar to depression, and XYS was able to reverse this behavior, indicating that Octs play a significant role in the development of depression and XYS may exert its antidepressant effects through the regulation of Octs. Furthermore, the study also found that dopamine uptake decreased after inhibiting the expression of Octs, and XYS-containing serum could reverse the downregulation of Oct1 and Oct3 and promote intracellular dopamine homeostasis in the astrocytes. Overall, XYS may exert antidepressant effects by promoting dopamine uptake to improve neurotransmitter transport by regulating the protein expression of Oct1 and Oct3 in astrocytes.

CONCLUSIONS

The antidepressant effect of XYS may be attributed to its ability to regulate the expression of Oct1 and Oct3 in astrocytes of the PFC, thereby promoting neurotransmitter transport.

Investigation into the impact of proton pump inhibitors on sertraline transport across the blood-brain barrier

As a widely used antidepressant that works by inhibiting the reuptake of serotonin, sertraline exerts an antidepressant effect depending on its concentration in the brain, which might be limited by the blood-brain barrier (BBB). It is highly possible to combine proton pump inhibitors (PPIs) with sertraline in clinical trials. Nevertheless, the role played by PPIs in regulating the transport of sertraline across the BBB remains unclear. Here, the impact of PPIs on the distribution of sertraline in the brain and the mechanisms involved were investigated. A mouse brain distribution study showed that Omeprazole (OME), Pantoprazole (PAN), Ilaprazole (ILA), and Esomeprazole (ESO) increased the area under the brain concentration-time curves (AUC) for sertraline by 2.02-, 3.18-, 3.04-, and 4.21-fold, respectively, after the 14-day administration of PPIs. Besides, PPIs significantly increased the permeability of sertraline in brain perfusion experiments, with PAN having the highest rank order, followed by ILA, OME, and ESO. In the tail suspension test (TST), co-administration PPI groups showed significantly shorter immobility time than the control group. In vitro, four PPIs inhibited sertraline efflux in breast cancer resistance protein (BCRP)-overexpressing MDCKII cells, and showed a mixed inhibition type. In this study, PPIs were further found to inhibit the mRNA and protein expression of brain BCRP. To sum up, the findings of this study revealed that PPIs could enhance the brain distribution and antidepressant effect of sertraline, which may be attributed to the inhibition of BCRP expression at the BBB by PPIs.

Stereoselective study of fluoxetine and norfluoxetine across the blood-brain barrier mediated by organic cation transporter 1/3 in rats using an enantioselective UPLC-MS/MS method

Fluoxetine (FLT) is a widely used antidepressant in clinical practice, which can be metabolized into active norfluoxetine (NFLT) in vivo. The stereoselectivity of FLT and NFLT enantiomers across the blood-brain barrier (BBB) is still to be clarified. In this study, accurate and reliable UPLC-MS/MS enantioselective analysis was established in rat plasma and brain. The characteristics of FLT and NFLT enantiomers across the BBB were studied by chemical knockout of rat transporters. We found that the dominant enantiomers of FLT and NFLT were S-FLT and R-NFLT, respectively, both in plasma and in brain. The FLT and NFLT enantiomers showed significant stereoselectivity across the BBB, and S-FLT and S-NFLT were the dominant configurations across the BBB. Chemical knockout of organic cation transporter 1 (OCT1) and OCT3 can affect the ratio of plasma FLT and NFLT enantiomers into the brain, suggesting that OCT1/3 is stereoselective for FLT and NFLT transport across the BBB.

Sub-chronic administration of fluoxetine does not alter prey-capture or predator avoidance behaviors in adult South African clawed frogs (Xenopus laevis)

Animals will halt foraging efforts and engage defensive behaviors in response to predator cues. Some researchers have proposed that the switch from appetitive to avoidance behavior resembles anxiety, but most work on this has been performed in a limited number of animal models, primarily zebrafish and rodents. We used adult South African clawed frogs (Xenopus laevis) to determine if the canonical anxiolytic fluoxetine alters predator-induced changes in appetitive and avoidance behavior in a laboratory-based trade-off task that mimics foraging/predator avoidance tradeoffs in the wild. We hypothesized that sub-chronic fluoxetine treatment (20 d) would not affect baseline behavior but would reverse predator-induced changes in food intake, appetitive and avoidance behavior, and the abundance of anxiety related gene transcripts in the optic tectum, a brain area central to ecological decision making in frogs. We found that fluoxetine significantly reduced baseline locomotion compared to vehicle-treated animals. Fluoxetine had no effect on appetitive and avoidance behaviors that were sensitive to predator cues in this assay and did not alter any of the anxiety-related transcripts in the tectum. We conclude that while peripheral sub-chronic administration of fluoxetine significantly reduces locomotion, it does not modify predator-induced changes in approach and avoidance behaviors in this assay. Our findings are not consistent with visual predator cues causing state anxiety in adult frogs.

Repurposable Drugs That Interact with Steroid Responsive Gene Targets for Inner Ear Disease

Corticosteroids, oral or transtympanic, remain the mainstay for inner ear diseases characterized by hearing fluctuation or sudden changes in hearing, including sudden sensorineural hearing loss (SSNHL), Meniere's disease (MD), and autoimmune inner ear disease (AIED). Despite their use across these diseases, the rate of complete recovery remains low, and results across the literature demonstrates significant heterogeneity with respect to the effect of corticosteroids, suggesting a need to identify more efficacious treatment options. Previously, our group has cross-referenced steroid-responsive genes in the cochlea with published single-cell and single-nucleus transcriptome datasets to demonstrate that steroid-responsive differentially regulated genes are expressed in spiral ganglion neurons (SGN) and stria vascularis (SV) cell types. These differentially regulated genes represent potential druggable gene targets. We utilized multiple gene target databases (DrugBank, Pharos, and LINCS) to identify orally administered, FDA approved medications that potentially target these genes. We identified 42 candidate drugs that have been shown to interact with these genes, with an emphasis on safety profile, and tolerability. This study utilizes multiple databases to identify drugs that can target a number of druggable genes in otologic disorders that are commonly treated with steroids, providing a basis for establishing novel repurposing treatment trials.