Loss of monocarboxylate transporter 1 aggravates white matter injury after experimental subarachnoid hemorrhage in rats

Monocarboxylic acid transporter 1(MCT1)maintains axonal function by transferring lactic acid from oligodendrocytes to axons.Subarachnoid hemorrhage(SAH)induces white matter injury,but the involvement of MCT1 is unclear.In this study,the SAH model of adult male Sprague-Dawley rats was used to explore the role of MCT1 in white matter injury after SAH.At 48 h after SAH,oligodendrocyte MCT1 was significantly reduced,and the exogenous overexpression of MCT1 significantly improved white matter integrity and long-term cognitive function.Motor training after SAH significantly increased the number of ITPR2+SOX10+oligodendrocytes and upregulated the level of MCT1,which was positively correlated with the behavioral ability of rats.In addition,miR-29b and miR-124 levels were significantly increased in SAH rats compared with non-SAH rats.Further intervention experiments showed that miR-29b and miR-124 could negatively regulate the level of MCT1.This study confirmed that the loss of MCT1 may be one of the mechanisms of white matter damage after SAH and may be caused by the negative regulation of miR-29b and miR-124.MCT1 may be involved in the neurological improvement of rehabilitation training after SAH.

Monocarboxylate transporter 4 plays a significant role in the neuroprotective mechanism of ischemic preconditioning in transient cerebral ischemia

Monocarboxylate transporters（MCTs）, which carry monocarboxylates such as lactate across biological membranes, have been associated with cerebral ischemia/reperfusion process. In this study, we studied the effect of ischemic preconditioning（IPC） on MCT4 immunoreactivity after 5 minutes of transient cerebral ischemia in the gerbil. Animals were randomly designated to four groups（sham-operated group, ischemia only group, IPC ＋ sham-operated group and IPC ＋ ischemia group）. A serious loss of neuron was found in the stratum pyramidale of the hippocampal CA1 region（CA1）, not CA2/3, of the ischemia-only group at 5 days post-ischemia; however, in the IPC ＋ ischemia groups, neurons in the stratum pyramidale of the CA1 were well protected. Weak MCT4 immunoreactivity was found in the stratum pyramidale of the CA1 in the sham-operated group. MCT4 immunoreactivity in the stratum pyramidale began to decrease at 2 days post-ischemia and was hardly detected at 5 days post-ischemia; at this time point, MCT4 immunoreactivity was newly expressed in astrocytes. In the IPC ＋ sham-operated group, MCT4 immunoreactivity in the stratum pyramidale of the CA1 was increased compared with the sham-operated group, and, in the IPC ＋ ischemia group, MCT4 immunoreactivity was also increased in the stratum pyramidale compared with the ischemia only group. Briefly, present findings show that IPC apparently protected CA1 pyramidal neurons and increased or maintained MCT4 expression in the stratum pyramidale of the CA1 after transient cerebral ischemia. Our findings suggest that MCT4 appears to play a significant role in the neuroprotective mechanism of IPC in the gerbil with transient cerebral ischemia.

Association between Alzheimer's disease pathogenesis and early demyelination and oligodendrocyte dysfunction

The APPSwe/PSEN1 dE9（APP/PS1） transgenic mouse model is an Alzheimer＇s disease mouse model exhibiting symptoms of dementia, and is commonly used to explore pathological changes in the development of Alzheimer＇s disease. Previous clinical autopsy and imaging studies suggest that Alzheimer＇s disease patients have white matter and oligodendrocyte damage, but the underlying mechanisms of these have not been revealed. Therefore, the present study used APP/PS1 mice to assess cognitive change, myelin loss, and corresponding changes in oligodendrocytes, and to explore the underlying mechanisms. Morris water maze tests were performed to evaluate cognitive change in APP/PS1 mice and normal C57 BL/6 mice aged 3 and 6 months. Luxol fast blue staining of the corpus callosum and quantitative reverse transcription-polymerase chain reaction（q RT-PCR） for myelin basic protein（MBP） mRNA were carried out to quantify myelin damage. Immunohistochemistry staining for NG2 and qRT-PCR for monocarboxylic acid transporter 1（MCT1） mRNA were conducted to assess corresponding changes in oligodendrocytes. Our results demonstrate that compared with C57 BL/6 mice, there was a downregulation of MBP mRNA in APP/PS1 mice aged 3 months. This became more obvious in APP/PS1 mice aged 6 months accompanied by other abnormalities such as prolonged escape latency in the Morris water maze test, shrinkage of the corpus callosum, upregulation of NG2-immunoreactive cells, and downregulation of MCT1 mRNA. These findings indicate that the involvement of early demyelination at 3 months and the oligodendrocyte dysfunction at 6 months in APP/PS1 mice are in association with Alzheimer＇s disease pathogenesis.