Myocardial infarction-induced hippocampal microtubule damage by cardiac originating microRNA-1 in mice.

Cardiovascular diseases are risk factors for dementia, but the mechanisms remain elusive. Here, we report that myocardial infarction (MI) generated by the ligation of the left coronary artery (LCA) could lead to increased miR-1 levels in the hippocampus and blood with neuronal microtubule damage and decreased TPPP/p25 protein expression in the hippocampus. These changes could be prevented by a knockdown of miR-1 using hippocampal stereotaxic injections of anti-miR-1 oligonucleotide fragments carried by a lentivirus vector (lenti-pre-AMO-miR-1). TPPP/p25 protein was downregulated by miR-1 overexpression, upregulated by miR-1 inhibition, and unchanged by binding-site mutations or miR-masks, indicating that the TPPP/p25 gene was a potential target for miR-1. Additionally, the pharmacological inhibition of sphingomyelinase by GW4869 to inhibit exosome generation in the heart significantly attenuated the increased miR-1 levels in the hippocampi of transgenic (Tg) and MI mice. Collectively, the present study demonstrates that MI could directly lead to neuronal microtubule damage independent of MI-induced chronic brain hypoperfusion but involving the overexpression of miR-1 in the hippocampus that was transported by exosomes from infarcted hearts. This study reveals a novel insight into the molecular mechanisms of heart-to-brain communication at the miRNA level.

Knockdown of MicroRNA-1 in the Hippocampus Ameliorates Myocardial Infarction Induced Impairment of Long-Term Potentiation.

BACKGROUNDS/AIMS: It has been reported that myocardial infarction (MI) is a risk factor for vascular dementia. However, the molecular mechanism remains largely unknown. METHODS: MI mice were generated by ligation of the left coronary artery (LCA) for 4 weeks. Passive and active avoidance tests were performed to evaluate the cognitive ability of MI mice. A theta-burst stimulation (TBS) protocol was applied to elicit long-term potentiation (LTP) of the perforant pathway-dentate gyrus synapse (PP-DG). Western blot analysis was employed to assess protein levels. RESULTS: In this study, we demonstrated that after 4 weeks of MI, C57BL/6 mice had significantly impaired memory. Compared with the sham group, in vivo physiological recording in the MI group revealed significantly decreased amplitude of population spikes (PS) with no effect on the latency and duration of the stimulus-response curve. The amplitude of LTP was markedly decreased in the MI group compared with the sham group. Further examination showed that the expression of the TBS-LTP-related proteins BDNF, GluA1 and phosphorylated GluA1 were all decreased in the MI group compared with those in the sham group. Strikingly, all these changes were prevented by hippocampal stereotaxic injection of an anti-miR-1 oligonucleotide fragment carried by a lentivirus vector (lenti-pre-AMO-1). CONCLUSION: MI induced cognitive decline and TBS-LTP impairment, and decreased BDNF and GluA1 phosphorylation levels from overexpression of miR-1ated were involved in this process.