Background: Abelmoschus manihot (L.) Medik ("Huangkui" in Chinese, HK) has been widely used for the treatment of kidney diseases. Nephrotoxicity is the side effect of cisplatin (CDDP), which greatly limits its clinical application. Therefore, CDDP could be used to establish the chronic kidney disease (CKD) model. However, the protective effects of HK on CDDP-induced CKD have not been investigated. Purpose: To explore the protective effect and underlying mechanisms of HK on multiple low-dose CDDP-induced CKD in rats by the integrated analysis of serum, kidney, and urine metabolomics and network pharmacology. Methods: The CKD model was induced by multiple low-dose CDDP. Body weight, organ index, serum biochemical, and kidney histology were examined to evaluate the effect of HK. Serum, kidney, and urine were collected and profiled by HILIC/RPLC-Q-TOF/MS-based metabolomics. Potential biomarkers (PBs) were screened according to the criteria of VIP >1, p < 0.01, and FC > 2, and then identified or assigned. The pathway analysis and PBs enrichment were conducted by MetaboAnalyst and ChemRICH. Furthermore, network pharmacology was adopted to dig out the active components and targets. Finally, the results from metabolomics and network pharmacology were integrated to confirm each other. Results: HK could recover the CDDP-induced abnormal pharmacological and metabolic profile changes. A total of 187 PBs were screened and identified from the serum, kidney, and urine metabolomics. Pathway analysis showed that multiple metabolic pathways, mainly related to amino acid and lipid metabolisms, were involved in the nephroprotective effect of HK, and especially, HK could significantly alleviate the disorder of tryptophan metabolism pathway in serum, kidney, and urine. Meanwhile, network pharmacology analysis revealed that 5 components in HK and 4 key genes could be responsible for the nephroprotection of HK, which also indicated that the metabolism of tryptophan played an important role in HK against CKD. Conclusion: HK has a nephroprotection on CDDP-induced CKD, mainly by restoring the dysregulation of tryptophan metabolism. Integrated analysis of serum, kidney, and urine metabolomics and network pharmacology was a powerful method for exploring pharmacological mechanisms and screening active components and targets of traditional Chinese medicine.

Mate choice was an important factor affecting the success rate of natural mating of captive giant pandas. The influencing factors and mechanisms of the mate preference of captive giant pandas were still unclear, and it was speculated that they might be related to the psychological stress caused by the long-term confined environment restricting their free choice of physiological needs. In order to test this hypothesis, this work explored the urinary metabolites of 6 adult captive male giant pandas during breeding period. Differences in metabolite levels in giant panda urine samples were analyzed via Ultra High Performance LC-MS (UHPLC/-MS) comparing preservation to loss of natural reproductive capacity and success to failure of mating choice, trying to understand the psychological feelings of captive giant pandas in the process of mate choice from the perspective of all metabolites and related biochemical pathways, and fully revealed the mechanism of decline of their natural reproductive ability. The analysis results indicated that the loss of natural mating behavior of adult captive male giant pandas might be related to the disorder of tryptophan metabolism pathway and inhibition of arginine synthesis; the reason for the failure of mating choice caused by decreased libido might be related to the temporary decrease of androgen contents caused by the down-regulated of TCA cycle function and galactose metabolic pathway. These findings not only provide that adult male giant pandas in captivity do have psychological frustration caused by the inability to freely choose their favorite mate or failure of mating preference, but also showed that the changes in stress-related metabolic pathways caused by psychological frustration were an important reason for the decline of natural mating behavior of adult captive male giant pandas.

As disorder of tryptophan metabolism is common in CKD, the rate-limiting enzyme of tryptophan, indoleamine-2,3-dioxygenase (IDO), has been reported to be involved in CKD, while the accurate mechanism remains unknown. This study was designed to explore correlations between IDO and kidney fibrosis after ischemia-reperfusion injury (IRI). Wild-type (WT) mice and IDO knockout (IDO-/-) mice were divided into the sham group and acute kidney injury (AKI) group. Mice in the sham group underwent dorsal incision and exposure of renal pedicle without clamping renal artery, while mice in the AKI group received unique renal artery IRI, and the contralateral kidney was removed at day 13 after IRI. Blood and IRI kidneys were collected at day 14. Kidney function was analyzed by measuring serum Cr and BUN. Morphology was analyzed by tissue periodic acid-Schiff (PAS) staining and Masson staining. Further, fibrosis markers and Wnt/β-catenin pathway proteins were determined by Western blot. Prostaglandin E2 (PGE2) was administrated for 2 weeks after the IRI mice model was established to observe whether it ameliorates kidney fibrosis after IRI. WT AKI mice revealed elevated expression of IDO compared with WT sham mice. Kidney function of IDO-/- AKI mice showed better than that of WT AKI mice. PAS staining exhibited less loss of tubular epithelial cells and atrophy tubules in IDO-/- AKI mice. Furthermore, kidney fibrosis areas and the expressions of fibrosis markers, including α-SMA, fibronectin, and vimentin, were increased in WT AKI mice. In addition, GSK-3β and β-catenin were significantly declined in IDO-/- AKI mice. On top of that, PGE2 administration revealed inhibited IDO expression and that reducing GSK-3β and β-catenin resulting in lower expressions of α-SMA, fibronectin, and vimentin in WT AKI mice. IRI could increase IDO expression to activate Wnt/β-catenin pathway resulting kidney fibrosis. PGE2 could ameliorate kidney fibrosis via inhibiting IDO expression.