MiR-122 Participates in Oxidative Stress and Apoptosis in STZ-Induced Pancreatic β Cells by Regulating PI3K/AKT Signaling Pathway

Insight into the Inter-Organ Crosstalk and Prognostic Role of Liver-Derived MicroRNAs in Metabolic Disease Progression

Dysfunctional hepatic metabolism has been linked to numerous diseases, including non-alcoholic fatty liver disease, the most common chronic liver disorder worldwide, which can progress to hepatic fibrosis, and is closely associated with insulin resistance and cardiovascular diseases. In addition, the liver secretes a wide array of metabolites, biomolecules, and microRNAs (miRNAs) and many of these secreted factors exert significant effects on metabolic processes both in the liver and in peripheral tissues. In this review, we summarize the involvement of liver-derived miRNAs in biological processes with an emphasis on delineating the communication between the liver and other tissues associated with metabolic disease progression. Furthermore, the review identifies the primary molecular targets by which miRNAs act. These consolidated findings from numerous studies provide insight into the underlying mechanism of various metabolic disease progression and suggest the possibility of using circulatory miRNAs as prognostic predictors and therapeutic targets for improving clinical intervention strategies.

Analysis of the Role of PI3K/Akt Pathway in the Realization of the Normalizing Effect of Low-Molecular-Weight Mimetics of NGF and BDNF on Activity of Prooxidant and Antioxidant Systems in C57BL/6 Mice with Modeled Diabetes

The effect of low-molecular-weight mimetics of NGF and BDNF (GK-2 and GSB-214 in a dose 0.5 mg/kg, respectively) on malondialdehyde content and activity of an antioxidant defense enzyme glutathione peroxidase was studied in experiments on C57BL/6 mice with streptozotocin-induced diabetes. An increase in the malondialdehyde content indicating enhanced formation of peroxidation products and a decrease of glutathione peroxidase activity in the blood plasma of untreated diabetic animals were revealed. Both studied mimetics were shown to attenuate the severity of these disorders. Since the ability of these compounds to activate the PI3K/Akt signaling pathway was previously demonstrated in vitro on HT-22 cell culture, we studied the effect of LY294002, an inhibitor of this pathway, on the above parameters. It was found that LY294002 attenuates the normalizing effect of GK-2 and GSB-214 only in relation to glutathione peroxidase activity, but not malondialdehyde level.

Fatty hepatocytes-derived exosomal miR-122 reduces immune function and antioxidant defence in Ctenopharyngodon idella kidney (CIK) cells

Exosomes are important for intercellular "cross talk", but the role of exosomes in communication between hepatocytes and C. idella kidney (CIK) cells remains unknown. In this study, we detected the changes in factors related to immune and oxidative stress to investigate the molecular mechanism by which fatty hepatocyte-derived exosomes (OA-Exos) reduced immunity and induced oxidative stress in CIK cells. After incubation of CIK cells by OA-Exos for 24 h, tumor necrosis factor-α (TNF-α), nuclear factor-κB (NF-κB) and interleukin-1β (IL-1β) were significantly upregulated in the OA-Exos group (P < 0.05), and Mn superoxide dismutase (Mn-SOD) and heme oxygenase-1 (HO-1) were significantly downregulated (P < 0.05). Surprisingly, miR-122 expression was also significantly elevated after OA-Exos incubation. We further identified the expression of miR-122 and found that it was notably increased in OA-Exos compared to hepatocyte-derived exosomes (Exos). Then we transfected CIK cells with miR-122 mimic, consistently, the expression of inflammatory cytokines was also significantly elevated (P < 0.05), and the expression of glutathione peroxidase (GPx), HO-1, and Mn-SOD were dramatically decreased (P < 0.05). Furthermore, HO-1 was improved to be a direct target of miR-122, and transfection with HO-1 siRNA indicated that changes in inflammatory cytokines and genes related to oxidative stress were consistent with the above results of CIK cells incubated with OA-Exos and miR-122 mimic. We concluded that OA-Exos may, through the miR-122/HO-1 pathway, reduce immune function and antioxidant defence in CIK cells.

Targeting the PI3K/Akt signaling pathway in pancreatic β-cells to enhance their survival and function: An emerging therapeutic strategy for type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease caused by the destruction of the insulin-producing β-cells within the pancreas. Islet transplantation represents one cure; however, during islet preparation and post transplantation significant amounts of β-cell death occur. Therefore, prevention and cure of T1D is dependent upon the preservation of β-cell function and the prevention of β-cell death. Phosphoinositide 3-kinase (PI3K)/Akt signaling represents a promising therapeutic target for T1D due to its pronounced effects on cellular survival, proliferation, and metabolism. A growing amount of evidence indicates that PI3K/Akt signaling is a critical determinant of β-cell mass and function. Modulation of the PI3K/Akt pathway, directly (via the use of highly specific protein and peptide-based biologics, excretory/secretory products of parasitic worms, and complex constituents of plant extracts) or indirectly (through microRNA interactions) can regulate the β-cell processes to ultimately determine the fate of β-cell mass. An important consideration is the identification of the specific PI3K/Akt pathway modulators that enhance β-cell function and prevent β-cell death without inducing excessive β-cell proliferation, which may carry carcinogenic side effects. Among potential PI3K/Akt pathway agonists, we have identified a novel parasite-derived protein, termed FhHDM-1 (Fasciola hepatica helminth defense molecule 1), which efficiently stimulates the PI3K/Akt pathway in β-cells to enhance function and prevent death without concomitantly inducing proliferation unlike several other identified stimulators of PI3K/Akt signaling . As such, FhHDM-1 will inform the design of biologics aimed at targeting the PI3K/Akt pathway to prevent/ameliorate not only T1D but also T2D, which is now widely recognized as an inflammatory disease characterized by β-cell dysfunction and death. This review will explore the modulation of the PI3K/Akt signaling pathway as a novel strategy to enhance β-cell function and survival.

Magnesium-L-threonate exhibited a neuroprotective effect against oxidative stress damage in HT22 cells and Alzheimer’s disease mouse model

BACKGROUND

Oxidative stress results in the production of excess reactive oxygen species (ROS) and triggers hippocampal neuronal damage as well as occupies a key role in the pathological mechanisms of neurodegenerative disorders such as Alzheimer’s disease (AD). A recent study confirmed that magnesium had an inhibitory effect against oxidative stress-related malondialdehyde in vitro. However, whether Magnesium-L-threonate (MgT) is capable of suppressing oxidative stress damage in amyloid β (Aβ)_25-35-treated HT22 cells and the AD mouse model still remains to be investigated.

AIM

To explore the neuroprotective effect of MgT against oxidative stress injury in vitro and in vivo, and investigate the mechanism.

METHODS

Aβ_25-35-induced HT22 cells were preconditioned with MgT for 12 h. APPswe/PS1dE9 (APP/PS1) mice were orally administered with MgT daily for 3 mo. After MgT treatment, the viability of Aβ_25-35-treated HT22 cells was determined via conducting cell counting kit-8 test and the cognition of APP/PS1 mice was measured through the Morris Water Maze. Flow cytometry experiments were applied to assess the ROS levels of HT22 cells and measure the apoptosis rate of HT22 cells or hippocampal neurons. Expression of B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X (Bax), hypoxia-inducible factor (HIF)-1α, NADPH oxidase (NOX) 4, Aβ_1-42 and phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) pathway proteins was quantified by Western blot.

RESULTS

In vitro data confirmed that Aβ_25–35-induced HT22 cells had a significantly lower cell viability, higher ROS level and higher apoptosis rates compared with those of control cells (all P < 0.001). MgT prevented the Aβ_25-35-triggered oxidative stress damage by elevating viability and decreasing ROS formation and apoptosis of HT22 cells (all P < 0.001). APP/PS1 mice exhibited worse cognitive performance and higher apoptosis rate of hippocampal neurons than wild-type (WT) mice (all P < 0.01). Meanwhile, significant higher expression of Aβ_1-42 and NOX4 proteins was detected in APP/PS1 mice than those of WT mice (both P < 0.01). MgT also ameliorated the cognitive deficit, suppressed the apoptosis of hippocampal neuron and downregulated the expression of Aβ_1-42 and NOX4 proteins in APP/PS1 mouse (all P < 0.05). Moreover, MgT intervention significantly downregulated HIF-1α and Bax, upregulated Bcl-2 and activated the PI3K/Akt pathway both in vitro and in vivo (all P < 0.05).

CONCLUSION

MgT exhibits neuroprotective effects against oxidative stress and hippocampal neuronal apoptosis in Aβ_25-35-treated HT22 cells and APP/PS1 mice.