Inhibition of miR31 and miR92a as Oncological Biomarkers in RKO Colon Cancer Cells Treated with Kaempferol-3-O-Glycoside Isolated from Black Bean

MicroRNAs (miRNAs) are small molecules of 19-23 nucleotides of RNA that act as regulators of the expression of proteins in eukaryotic cells. Currently, the participation of miRNAs in the development of different types of cancer has been observed. To evaluate the inhibitory effect of kaempferol-3-O-glycoside on the expression of oncological biomarkers, miR31 and miR92a in a colon cancer cell line (RKO) were analyzed. Cells were cultured and treated with 1 mM kaempferol-3-O-glycoside isolated from black bean. Expression levels of miR31 and miR92a were evaluated by real-time PCR using TaqMan probes; in addition, two oncogenes (KRAS and c-MYC) and two tumor suppressors (AMP-activated protein kinase [AMPK] and adenomatous tumors of polyposis coli [APC]) were quantified to validate the biological effects; normalization of expression levels were carried out by 2^-ΔΔCt. Results were analyzed by one-way ANOVA. The expression levels of miR31, miR92a, KRAS oncogene, and the c-MYC transcription factor were subexpressed upon 72 h post-treatment with kaempferol-3-O-glycoside compared with the control without treatment (P < .05); in contrast, the tumor suppressor genes AMPK (∼4.85, P = .005) and APC (∼2.71, P = .066) tumor suppressors genes were overexpressed. Our results showed the inhibitory effect of isolated black bean flavonoid kaempferol-3-O-glycoside on cancer biomarkers: miR31 and miR92a; based on our results, this flavonoid may have interesting nutritional, therapeutic, and/or prophylactic applications to combat colon cancer.

Correcting miR92a-vGAT-Mediated GABAergic Dysfunctions Rescues Human Tau-Induced Anxiety in Mice

Patients with Alzheimer's disease (AD) commonly show anxiety behaviors, but the molecular mechanisms are not clear and no efficient intervention exists. Here, we found that overexpression of human wild-type, full-length tau (termed htau) in hippocampus significantly decreased the extracellular γ-aminobutyric acid (GABA) level with inhibition of γ oscillation and the evoked inhibitory postsynaptic potential (eIPSP). With tau accumulation, the mice show age-dependent anxiety behaviors. Among the factors responsible for GABA synthesis, release, uptake, and transport, we found that accumulation of htau selectively suppressed expression of the intracellular vesicular GABA transporter (vGAT). Tau accumulation increased miR92a, which targeted vGAT mRNA 3' UTR and inhibited vGAT translation. Importantly, we found that upregulating GABA tones by intraperitoneal injection of midazolam (a GABA agonist), ChR2-mediated photostimulating and overexpressing vGAT, or blocking miR92a by using specific antagomir or inhibitor efficiently rescued the htau-induced GABAergic dysfunctions with attenuation of anxiety. Finally, we also demonstrated that vGAT level decreased while the miR92a increased in the AD brains. These findings demonstrate that the AD-like tau accumulation induces anxiety through disrupting miR92a-vGAT-GABA signaling, which reveals molecular mechanisms underlying the anxiety behavior in AD patients and potentially leads to the development of new therapeutics for tauopathies.