[Role of SCO1 in regulating microglial mitochondrial copper accumulation in neurological damage of mice exposed to lead and high-glucose diet].

Objective: To investigate the mechanism of neurological damage in mice induced by Pb exposure combined with high glucose.

Methods: SPF C57 mice were randomly divided into a control group, a Pb group, a high-glucose diet group, and a Pb + high-glucose diet group. Mice in the control group and the Pb group were given basic feed, while those in the high-glucose diet group and the Pb + high-glucose diet group were given a high-glucose diet(50.26% carbohydrates, 21.44% fat, 17.45% protein, 4.21% minerals, and 3.64% fiber). The control group and the high-glucose diet group had free access to pure water, while the Pb group and the Pb + high-glucose diet group were given free access to 250 mg/L Pb acetate water for 12 weeks. The sucrose water preference test and elevated plus maze test were used to assess anxiety and depression-like behaviors in mice. The murine microglial cell line BV-2 was randomly divided into a control group, a Pb group, a high-glucose environment group, and a Pb + high-glucose environment group. The control group received no treatment, the Pb group was given 10 μmol/L Pb acetate, the high-glucose environment group was given 40 mmol/L glucose, and the Pb + high-glucose environment group was given 10 μmol/L Pb acetate and 40 mmol/L glucose for 24 hours. siRNA transfection in BV-2 cells was used to establish a synthesis of cytochrome C oxidase 1(SCO1) knockdown cell model(siSCO1 cells), which were exposed to 10 μmol/L Pb acetate and 40 mmol/L glucose for 24 hours. ICP-MS, immunofluorescence, and kit method were applied to detect copper and Pb content in mice cortex and BV-2 cells. Kits were used to detect superoxide dismutase(SOD) and catalase(CAT) in mice cortex and BV-2 cells. Western blot was used to measure the protein expression of SCO1, ionized calcium binding adaptor molecule 1(Iba-1), interleukin-1β(IL-1β) and interleukin-6(IL-6) in mice cortex and BV-2 cells.

Results: The sucrose water preference test result showed that the sucrose water preference rate of mice in the Pb + high-glucose diet group was 31.00%, which was significantly lower than that in the Pb group and the high-glucose diet group(P<0.05). The elevated plus maze result showed that the percentage of entries into the open arms(27.20%) and the percentage of time spent in the open arms(24.20%) of mice in the Pb + high-glucose diet group were significantly lower than those in the Pb group and the high-glucose diet group(P<0.05). The content of SOD in the cerebral cortex of mice in the Pb + high-glucose diet group was 210.96 U/mg prot and the content of CAT was 108.94 U/mg prot, which were significantly lower than those in the Pb group and the high-glucose diet group(P<0.05). The total copper content in the cerebral cortex of mice in the Pb + high-glucose diet group was 4.41 μg/g, which was significantly higher than that in the Pb or high-glucose diet groups alone(P<0.05). Additionally, the expression of SCO1 protein in the cerebral cortex of mice in the Pb + high-glucose diet group was 1.86 times that of the control group, 1.23 times that of the Pb group, and 1.21 times that of the high-glucose diet group(P<0.05). The expression of Iba1, IL-1β, and IL-6 proteins in the cerebral cortex of mice in the Pb + high-glucose diet group was significantly higher than that in the Pb group and the high-glucose diet group(P<0.05). After knocking down SCO1, the average fluorescence density of total Pb in BV-2 cells exposed to Pb and high-glucose combined showed no change, but the copper content in the mitochondria of BV-2 cells was 0.07 nmol/10~6 cells, which was lower than that in the non-knockdown BV-2 cells(P<0.05). Moreover, knocking down SCO1 led to an increase in the content of SOD and CAT in the mitochondria of BV-2 cells exposed to Pb and high-glucose combined, and a decrease in the expression of Iba1 and IL-1β proteins(P<0.05).

Conclision: High-glucose can exacerbate anxiety and depression-like behaviors in mice with Pb exposure, which may be related to the mitochondrial SCO1 increase, which result ing in elevated mitochondrial copper content in microglial cells, thereby causing inflammatory activation of microglial cells.