Enteric glial cells exert neuroprotection from hyperglycemia-induced damage via Akt/GSK3β pathway

The complex landscape of intracellular signalling in protein modification under hyperglycaemic stress leading to metabolic disorders

Hyperglycaemia is a life-threatening risk factor that occurs in both chronic and acute phases and has been linked to causing injury to many organs. Protein modification was triggered by hyperglycaemic stress, which resulted in pathogenic alterations such as impaired cellular function and tissue damage. Dysregulation in cellular function increases the condition associated with metabolic disorders, including cardiovascular diseases, nephropathy, retinopathy, and neuropathy. Hyperglycaemic stress also increases the proliferation of cancer cells. The major areas of experimental biomedical research have focused on the underlying mechanisms involved in the cellular signalling systems involved in diabetes-associated chronic hyperglycaemia. Reactive oxygen species and oxidative stress generated by hyperglycaemia modify many intracellular signalling pathways that result in insulin resistance and β-cell function degradation. The dysregulation of post translational modification in β cells is clinically associated with the development of diabetes mellitus and its associated diseases. This review will discuss the effect of hyperglycaemic stress on protein modification and the cellular signalling involved in it. The focus will be on the significant molecular changes associated with severe metabolic disorders.

Ji-Chuan decoction ameliorates slow transit constipation via regulation of intestinal glial cell apoptosis

BACKGROUND

Slow transit constipation (STC) is a common intestinal disease with increasing incidence. STC results from various factors, such as the enteric nervous system and metabolic changes. As a classical formula of traditional Chinese medicine, Ji-Chuan decoction (JCD) has been extensively and effectively used in STC treatment, yet its pharmacological mechanism remains unclear.

AIM

To explore the integrated regulatory pattern of JCD against STC through hyphenated techniques from metabolism, network pharmacology and molecular methods.

METHODS

STC model mice were generated by intragastric administration of compound diphenoxylate (10 mg/kg/d) for 14 d. The STC mice in the low dose of JCD (3.04 g/kg), middle dose of JCD (6.08 g/kg) and high dose of JCD (12.16 g/kg) groups were orally administered JCD solution once a day for 2 wk. The acetylcholine (ACH) level was examined by enzyme-linked immunosorbent assay. The pathological features of colon tissue were observed by hematoxylin and eosin staining. The differentially expressed metabolites and metabolic pathways were tested by nontargeted metabolomics. The main targets and core ingredients of JCD were identified by network pharmacology, and the expression of AKT was confirmed by immunohistochemistry. Finally, the pathways involved in JCD treatment were predicted using a combination of differentially expressed metabolites and targets, and intestinal glial cell apoptosis was demonstrated by immunofluorescence.

RESULTS

JCD significantly promoted intestinal motility, increased the levels of the excitatory neurotransmitter ACH and reduced intestinal inflammation in STC mice. Untargeted metabolomics results showed that JCD significantly restored metabolic dysfunction and significantly affected taurine and hypotaurine metabolism. Network pharmacology and molecular experiments showed that JCD regulates AKT protein expression, and the core component is quercetin. Combined analysis demonstrated that apoptosis may be an important mechanism by which JCD relieves constipation. Further experiments showed that JCD reduced enteric glial cell (EGC) apoptosis.

CONCLUSION

This work demonstrated that reducing EGC apoptosis may be the critical mechanism by which JCD treats STC. These findings call for further molecular research to facilitate the clinical application of JCD.

Insulin and α-Tocopherol Enhance the Protective Effect of Each Other on Brain Cortical Neurons under Oxidative Stress Conditions and in Rat Two-Vessel Forebrain Ischemia/Reperfusion Injury

Clinical trials show that insulin administered intranasally is a promising drug to treat neurodegenerative diseases, but at high doses its use may result in cerebral insulin resistance. Identifying compounds which could enhance the protective effects of insulin, may be helpful to reduce its effective dose. Our aim was thus to study the efficiency of combined use of insulin and α-tocopherol (α-T) to increase the viability of cultured cortical neurons under oxidative stress conditions and to normalize the metabolic disturbances caused by free radical reaction activation in brain cortex of rats with two-vessel forebrain ischemia/reperfusion injury. Immunoblotting, flow cytometry, colorimetric, and fluorometric techniques were used. α-T enhanced the protective and antioxidative effects of insulin on neurons in oxidative stress, their effects were additive. At the late stages of oxidative stress, the combined action of insulin and α-T increased Akt-kinase activity, inactivated GSK-3beta and normalized ERK1/2 activity in cortical neurons, it was more effective than either drug action. In the brain cortex, ischemia/reperfusion increased the lipid peroxidation product content and caused Na⁺,K⁺-ATPase oxidative inactivation. Co-administration of insulin (intranasally, 0.25 IU/rat) and α-T (orally, 50 mg/kg) led to a more pronounced normalization of the levels of Schiff bases, conjugated dienes and trienes and Na⁺,K⁺-ATPase activity than administration of each drug alone. Thus, α-T enhances the protective effects of insulin on cultured cortical neurons in oxidative stress and in the brain cortex of rats with cerebral ischemia/reperfusion injury.

Neuroprotective effects of tetrahydroxystilbene glucoside against rotenone-induced toxicity in PC12 cells

To investigate the mechanism of the protective effect of tetrahydroxystilbene glucoside (TSG) on nerve cells, an injury model induced by rotenone in PC12 cells was constructed. Cell viability was detected by using CCK8 assay. Apoptosis was detected by using flow cytometry. The mitochondrial membrane potential (MMP) was detected by using the fluorescent probe JC-1. Generation of reactive oxygen species (ROS) in PC12 cells was determined using the CM-H₂DCFDA probe. Protein expression in PC12 cells was detected using western blotting. The results showed that TSG (20-100 μM) attenuated the cytotoxic effects of rotenone on PC12 cells. TSG pretreatment attenuated the apoptosis rate, the degradation of PARP and the activation of cleaved caspase 3, which was induced by rotenone. TSG can significantly reduce the effect of rotenone on the reduction of MMP and the expression of cytoC in the cytosolic fraction. TSG attenuated rotenone-induced de-phosphorylation and mitochondrial translocation of cofilin, as well as rotenone-induced accumulation of ROS. The western blot results showed that ROT could decrease the expression level of p-GSK-3β and p-AKT, and TSG could weaken these effects of rotenone. In addition, TSG increased the expression level of Nrf2 in the nuclear fraction. These results suggest that TSG could protect PC12 cells against rotenone through multiple pathways. Thus, TSG has the potential to become a novel neuroprotective agent.