Effect of Chronic Administration of Low Dose Rapamycin on Development and Immunity in Young Rats.

Zhenya Lu,Michael Wong,Linglin Chen,Yuemin Ding,Ling-Hui Zeng,Jianxiang Liu,Furong Liu,Huadan Zhang

doi:10.1371/journal.pone.0135256

Zhenya Lu, Michael Wong + Show 6 more

Open Access

https://doi.org/10.1371/journal.pone.0135256

Copy DOI

Abstract

Mammalian target of rapamycin (mTOR) regulates cell growth, cell differentiation and protein synthesis. Rapamycin, an inhibitor of mTOR, has been widely used as an immunosuppressant and anti-cancer drug. Recently, mTOR inhibitors have also been reported to be a potential anti-epileptic drug, which may be effective when used in young patients with genetic epilepsy. Thus, a suitable dose of rapamycin which can maintain the normal function of mTOR and has fewer side effects ideally should be identified. In the present study, we first detected changes in marker proteins of mTOR signaling pathway during development. Then we determined the dose of rapamycin by treating rats of 2 weeks of age with different doses of rapamycin for 3 days and detected its effect on mTOR pathway. Young rats were then treated with a suitable dose of rapamycin for 4 weeks and the effect of rapamycin on mTOR, development and immunity were investigated. We found that the expression of the marker proteins of mTOR pathway was changed during development in brain hippocampus and neocortex. After 3 days of treanent, 0.03 mg/kg rapamycin had no effect on phospho-S6, whereas 0.1, 0.3, 1.0 and 3.0 mg/kg rapamycin inhibited phospho-S6 in a dose-dependent manner. However, only 1.0 mg/kg and 3.0 mg/kg rapamycin inhibited phospho-S6 after 4 weeks treatment of rapamycin. Parallel to this result, rats treated with 0.1 and 0.3 mg/kg rapamycin had no obvious adverse effects, whereas rats treated with 1.0 and 3.0 mg/kg rapamycin showed significant decreases in body, spleen and thymus weight. Additionally, rats treated with 1.0 and 3.0 mg/kg rapamycin exhibited cognitive impairment and anxiety as evident by maze and open field experiments. Furthermore, the content of IL-1β, IL-2, IFN-γ, TNF-α in serum and cerebral cortex were significantly decreased in 1.0 and 3.0 mg/kg rapamycin-treated rats. The expression of DCX was also significantly decreased in 1.0 and 3.0 mg/kg rapamycin-treated rats. However, rats treated with 1.0 mg/ kg rapamycin exhibited fewer and milder side effects than those treated with 3.0 mg/kg. In summary, all these data suggest that there is not a rapamycin dose that can inhibit mTOR for epilepsy without causing any side effects, but 1 mg /kg may be the optimal dose for young rats for suppressing mTOR with relatively few side effects.

Highlights

Epilepsy is the third most common major neurological disease characterized by recurrent, unprovoked seizures
In attempting to develop more effective drugs for epilepsy, the mammalian target of rapamycin signaling pathway has recently been investigated as a regulator of epileptogenesis [5,6,7,8]. mTOR pathway receives information from nutrients, growth factors, cytokines, and hormones through tyrosine kinase receptors, and plays an essential role in cell growth, differentiation, proliferation, and protein synthesis via phosphorylation of a number of translational regulators such as ribosomal S6 kinase
The relationship between mTOR pathway activation and epilepsy has been first implicated in genetic epilepsy using transgenic knockout mouse models of tuberous sclerosis complex and PTEN [5,6], and has been examined in acquired epilepsy in animal models of temporal lobe epilepsy induced by kainic acid (KA) or pilocarpine [7,8]

Summary

Introduction

Epilepsy is the third most common major neurological disease characterized by recurrent, unprovoked seizures. It affects about 50 million people around the world and is increasingly recognized as a disease that results in a range of comorbidities [1,2]. In attempting to develop more effective drugs for epilepsy, the mammalian target of rapamycin (mTOR) signaling pathway has recently been investigated as a regulator of epileptogenesis [5,6,7,8]. MTOR, a common protein kinase, is the key target protein kinase implicated in a large variety of physiological functions [9,10]. Hyperactivation of mTOR pathway has been established in hypoxia-induced neonatal seizures in animal models [11,12]

Methods

Results

Conclusion