P19 S-propargyl-cysteine (SPRC) attenuates cognitive impairment in APP/PS1 mice and protects neurons against glial overactivation induced by Aβ1−40 via modulation of cystathionine-β-synthase

Abstract

Background Hydrogen sulfide (H2S) plays an important role in central nervous system (CNS). In CNS, H2S production is mainly related to cystathionine β-synthetase (CBS), which are enriched in astrocytes. Many reports have documented that CBS activity and hydrogen sulfide is significantly decreased in the brain of Alzheimer’s disease patients. Thus therapeutic strategies based on modulating CBS might be promising. In this study, we investigated possible neuroprotective effect and mechanisms of SPRC in astrocytes and APP/PS1 mice. Methods Double transgenic mice expressing mutant genes for amyloid precursor protein and presenilin1 (APP/PS1) were tested in Morris water maze (MWM) and novel object recognition (NOR) behavioral studies for cognitive evaluations. Forty-nine 12-month-old mice were divided into five groups: wild-type group, APP/PS1 group, APP/PS1 + 100 mg/kg or 200 mg/kg SPRC group, APP/PS1+ Donepezil group. Radioactive sulfur-35-labeled SPRC were administered by gavage to relatively quantify drug distributions in various brain areas. Immunocytochemistry (IHC) staining, Congo red stain and ELISA were performed for evaluating astrogliosis, Amyloid-β (Aβ) load and ratio of Aβ1−42/Aβ1−40. Transmission electron microscope (TEM) was applied to observe ultrastructure change of hippocampus. CBS enzymatic activity was determined by colorimetry and protein expressions were evaluated by Western blot assay. For in vitro study, purified primary astrocytes were stimulated with Aβ1−40 or were pretreated with SPRC before Aβ1−40 treatment. SRB assay, Griess reaction and enzyme linked immunosorbent assay (ELISA) were applied to measure cell viability, nitrites production and proinflammatory cytokines, respectively. CBS-small interfering RNA (CBS siRNA) and a CBS inhibitor amino-oxyacetic acid (AOAA) were applied to investigate possible role of CBS in neuroprotective actions of SPRC in inhibiting overactivated astrocytes. In addition, a glia/neuron co-culture system was used to investigate neuron’s behavior in the presence of differently pretreated astrocytes. Results Sulfur-35-labeled SPRC could enter blood–brain barrier and widely distributed in different brain areas with a relative high concentration in hippocampus and striatum. Compared to APP/PS1 group, mice treated with 100 mg/kg and 200 mg/kg SPRC showed improved cognitive performances both in MWM and NOR tests. Observations by TEM and IHC showed that less dark neurons, decreased lipofuscin deposition and astrogliosis were found in the hippocampus. Neuroinflammation was alleviated as phosphorylations of NF-B and MAPK pathways were suppressed in SPRC treated groups. SPRC could reduce ratio of Aβ1−42/Aβ1−40 of insoluble fraction but not that of soluble fraction. SPRC could also increased activity and expression of CBS, elevate concentration of hydrogen sulfide in the plasma and brain tissue of mice, suppress TNF-α and nitrite production of astrocytes activated by Aβ1−40 treatment. Co-culture assay showed that pretreatment of astrocytes with SPRC could significantly increase neuronal viability and inhibit synaptophysin degradation in neurons. These neuroprotective effects could be abolished by CBS siRNA or AOAA. Conclusions Our study demonstrated that SPRC could ameliorate cognitive performances of APP/PS1 mice, suppress overactivation of astrocytes and alleviate neuroinflammation at least partially via CBS/H2S pathway in the CNS. Therefore, we concluded that SPRC could serve as a CBS modulator in treating AD and might be a drug candidate in the future.