Sodium P-Aminosalicylic Acid Improved Manganese-Induced Learning and Memory Dysfunction via Restoring the Ultrastructural Alterations and γ-Aminobutyric Acid Metabolism Imbalance in the Basal Ganglia

Abstract

Excessive intake of manganese (Mn) may cause neurotoxicity. Sodium para-aminosalicylic acid (PAS-Na) has been used successfully in the treatment of Mn-induced neurotoxicity. The γ-aminobutyric acid (GABA) is related with learning and memory abilities. However, the mechanism of PAS-Na on improving Mn-induced behavioral deficits is unclear. The current study was aimed to investigate the effects of PAS-Na on Mn-induced behavioral deficits and the involvement of ultrastructural alterations and γ-aminobutyric acid (GABA) metabolism in the basal ganglia of rats. Sprague-Dawley rats received daily intraperitoneally injections of 15 mg/kg MnCl.4HO, 5d/week for 4 weeks, followed by a daily back subcutaneously (sc.) dose of PAS-Na (100 and 200 mg/kg), 5 days/week for another 3 or 6 weeks. Mn exposure for 4 weeks and then ceased Mn exposure for 3 or 6 weeks impaired spatial learning and memory abilities, and these effects were long-lasting. Moreover, Mn exposure caused ultrastructural alterations in the basal ganglia expressed as swollen neuronal with increasing the electron density in the protrusions structure and fuzzed the interval of neuropil, together with swollen, focal hyperplasia, and hypertrophy of astrocytes. Additionally, the results also indicated that Mn exposure increased Glu/GABA values as by feedback loops controlling GAT-1, GABA mRNA and GABA protein expression through decreasing GABA transporter 1(GAT-1) and GABA A receptor (GABA) mRNA expression, and increasing GABA protein expression in the basal ganglia. But Mn exposure had no effects on GAT-1 protein expression. PAS-Na treatment for 3 or 6 weeks effectively restored the above-mentioned adverse effects induced by Mn. In conclusion, these findings suggest the involvement of GABA metabolism and ultrastructural alterations of basal ganglia in PAS-Na's protective effects on the spatial learning and memory abilities.

Sodium p-Aminosalicylic Acid Reverses Sub-Chronic Manganese-Induced Impairments of Spatial Learning and Memory Abilities in Rats, but Fails to Restore γ-Aminobutyric Acid Levels

“…injections [30]. Lastly, the dosing regimen chosen in the present study and the consequent neurotoxicity effects were in line with previous publications conducted in the laboratory [31,41]. Therefore, the dosage of Mn exposure in our rat model was within the reasonable range according to previous human and animal findings.…”

“…The MWM test was performed within 24 h after the final administration, in order to assess the spatial learning and memory ability of the experimental animals according to previous studies [31]. The apparatus consisted of a water pool (210 cm diameter × 60 cm height, and colored with a black non-toxic dye).…”

“…GABA levels in the basal ganglia were measured by using high performance liquid chromatography (HPLC) analysis, as previously described [31,32]. The total protein concentrations in the lysates were determined with a BCA kit (Beyotime Laboratories Inc., Shanghai, China).…”

“…One tube was reacted for 30 min at 37 °C with constant shaking; the other tube was stopped immediately upon the addition of perchlorate buffer (contains 0.5 mol/L acetic acid, 0.5 mol/L sodium acetate, and 0.4 mol/L sodium perchlorate) to the supernatant. After centrifugation, the supernatant was analyzed by HPLC [31,32]. The GAD activity was calculated as the reaction rate of the newly synthesized GABA (total GABA level in the reaction tube minus the original GABA level), and was then normalized to the total protein concentrations in the lysates.…”

“…The mRNA and protein expression of the GABA A receptor (GABA A ) and GABA transporter 1 (GAT-1) in the basal ganglia were analyzed by RT-PCR and western blotting, respectively, as previously described [31]. The tissues were homogenized on ice with the RIPA buffer (150 mM NaCl, 50 mM TrisHCl pH 7.4, 1 mM EDTA, 1% Triton X-100, 0.5% DOC, and 0.1% SDS), with the addition of protease inhibitors (1 mM phenylmethylsulfonyl fluoride, 10 μg/mL pepstatin A, 10 μg/mL leupeptin, 10 μg/mL aprotinin).…”