Investigation of synergistic mechanism and identification of interaction site of aldose reductase with the combination of gigantol and syringic acid for prevention of diabetic cataract.

BACKGROUND: Gigantol and syringic acid (SA) have been shown to synergistically prevent formation of diabetic cataract (DC). However, the exact mechanism of this effect is unknown. Here, we investigate the effect of these compounds on the activity of aldose reductase (AR) and cataract formation. METHODS: We examined the synergistic anti-cataract efficacy of gigantol and SA in the high glucose- and streptozotocin -induced DC rat model; synergism was evaluated using Jin's formula. We investigated possible mechanisms of action by measuring AR expression and activity and levels of sorbitol using enzyme kinetics, Western blot, and RT-PCR. Finally, we examined binding interaction between AR and both compounds using a combination of site-directed mutagenesis, recombinant expression of wild-type and mutant proteins, and enzyme kinetics. RESULTS: Combination treatment of gigantol and SA synergistically protected both HLECs(human lens epithelial cells) grown in vitro and DC formation in STZ-induced rats in vivo. Synergism was attributed to inhibition of AR activity, downregulation of AR expression via impaired transcription, and decreased sorbitol levels. Enzyme kinetics studies showed that the activity of an AR Asn160Ala mutant protein was significantly decreased compared to wild-type AR, confirming that Asn160 is a key residue for interaction between AR and both compounds. CONCLUSION: Combined administration of gigantol and SA synergize to enhance anti-cataract efficacy. The synergistic effect is mainly attributed to disruption of the polyol pathway and inhibition of AR activity.

[Experimental study on Dendrobium candidum polysaccharides on promotion of hair growth].

OBJECTIVE: To observe the effect and mechanism of Dendrobium candidum polysaccharides (DCP) in promoting hair growth, in order to lay a foundation for the development and utilization of D. candidum. METHOD: The water-extraction and alcohol-precipitation method was adopted to extract DCP, and the phenol-sulphuric acid method was used to determine its content. Thirty C57BL6J mice were collected to establish the hair loss model with hair removal cream. They were randomly divided into the control group, the positive control group and the DCP group, and given 0.2 mL of ultra-pure water, minoxidil tincture and DCP (5.0 g x L(-1)) 21 days. The mice hair growth scoring standard was adopted to evaluate the hair growth of C57BL/6J mice at 7, 14 d. The hairs in unit hair-losing areas of treated C57BL/6J mice at 21 d were weighed to evaluate the effect of DCP on the promotion of hair growth. MTT assay and RT-PCR method were used to evaluate the effect of DCP on the proliferatin of HaCaT cells and the mRNA expression of VEGF in HaCaT cells. RESULT: The extraction percent of DCP was 29.87%, and its content was 79.65%. The average scores for the hair growth and weight of C57BL/6J mice of DCP group were much higher than the control group. The survival rate and mRNA expression of VEGF of HaCaT cells were much higher than the control group. CONCLUSION: DCP has the effect in promoting hair growth. Its mechanism may be related to the up-regulation of the mRNA expression of VEGF.

[Experimental study on preclinical quality control, urgent poison and irritation of Dendrobium aurantiacum eye drops, a class I new drug against diabetic cataract].

To establish a quality control method of Dendrobium aurantiacum eye drops, in order to evaluate acute toxicity, irritation and irritability and lay a foundation for its development and utilization in the future. The content of gigantol and SA in D. aurantiacum eye drops were determined by high-performance liquid chromatography (HPLC). The linear ranges of gigantol and SA were 0.040 8-1.530 0 g x L(-1) (r = 0.999 9) and 0.100 8-0.504 0 g x L(-1) (r = 0.999 9), with the average recoveries being 100.8%, 99.84%, and RSD being 1.4%, 1.8% (n = 9) respectively. The sample solution was stable at room temperature within 72 h. The acute toxicity test showed no toxic reaction of D. aurantiacum eye drops in mice. The irritating test for single-dose and multiple-dose administrations of D. aurantiacum eye drops and physiological saline in rabbit eyes and skin, as well as the allergic test in guinea pigs showed no eye irritation and skin irritation and irritability. These findings indicated that D. aurantiacum eye drops are safe and stable, with a good druggability.

[Study on anti-cataract effect of gigantol combined with syringic acid and their mechanism].

OBJECTIVE: To study the anti-cataract effect of gigantol combined with syringic acid and their action mechanism. METHOD: H202-induced lens oxidative injury in vitro rat model was establish to observe the impact of gigantol combined with syringic acid on lens transparency under a dissecting microscope. D-galactose-induced cataract rat model was established to observe the impact of gigantol combined with syringic acid on lens transparency under a slit-lamp. UV spectrophotometry was adopted to detect the inhibitory activity of gigantol combined with syringic acid against AR. Molecular docking method was used to detect binding sites, binding types and pharmacophores of gigantol combined with syringic acid in prohibiting aldose reductase. RESULT: Both in vitro and in vivo experiments showed a good anti-sugar cataract activity in the combination of gigantol and syringic acid and a better collaborative effect than single component-gigantol and syringic acid and positive control drug Catalin. Molecular docking and dynamic simulation showed their collaborative AR-inhibiting amino acid residue was Asn160 and the major acting force was Van der Waals' force, which formed common pharmacophores. CONCLUSION: Gigantol combined with syringic acid shows good anti-cataract, their action mechanism is reflected in their good collaborative inhibitory effect on AR.