Myricetin induces M2 macrophage polarization to alleviate renal tubulointerstitial fibrosis in diabetic nephropathy via PI3K/Akt pathway

World Journal of Diabetes · 9 authors, 9 centres

AI SUMMARY

POPULATIONDb/db diabetic mice (in vivo) and RAW 264.7 macrophages (in vitro)

INTERVENTIONMyricetin (50 or 100 mg/kg intragastrically daily for 12 weeks in vivo; 25 μM for 24 h in vitro)

COMPARISONVehicle-treated db/db mice (in vivo) or high-glucose (33.3 mM) treated RAW 264.7 cells (in vitro); also compared with irbesartan (in vivo) and LY294002 (PI3K/Akt inhibitor, in vitro)

This summary was generated by AI from a single paper. It has not been reviewed by a clinician and is not clinical advice. Verify against the source before acting on it.

AGENT 01 · STRUCTURED SUMMARY

TRACE TO SOURCE

“

TL;DR

Myricetin, a flavonoid, alleviates kidney injury and fibrosis in diabetic nephropathy (DN) mice by promoting M2 macrophage polarization via the PI3K/Akt signaling pathway. In db/db mice, myricetin (50 or 100 mg/kg) reduced blood glucose, kidney injury markers, and fibrosis, while in RAW 264.7 cells, it inhibited M1 polarization and inflammatory cytokines. These findings suggest myricetin as a potential therapeutic for DN by targeting macrophage polarization.

Full summary

3,819 CHARS

**Background:** Diabetic nephropathy (DN) is a leading cause of end-stage renal disease, with limited effective therapies. Myricetin, a flavonoid found in Abelmoschus manihot, has shown anti-inflammatory and anti-diabetic properties, but its mechanism in DN is unclear. This study investigates myricetin's effects on DN and its potential mechanism involving macrophage polarization and the PI3K/Akt pathway.

**Methods:** In vivo, 6-week-old db/db mice (a model of type 2 diabetes) were treated with myricetin (50 or 100 mg/kg) or irbesartan (positive control) intragastrically daily for 12 weeks. Blood and urine parameters (blood glucose, serum creatinine, urine albumin-to-creatinine ratio [uACR], creatinine clearance) were measured every 4 weeks. Renal histopathology was assessed using hematoxylin and eosin (HE), periodic acid-Schiff (PAS), Masson's trichrome, and Sirius-red staining. Kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) were measured by qRT-PCR and western blotting. Inflammatory cytokines (TNF-α, IL-6, IL-1β, IL-10) and macrophage markers (F4/80, CD86, CD206) were analyzed by immunofluorescence, ELISA, and flow cytometry. Fibrosis markers (Col1a1, α-SMA) were assessed by immunofluorescence, qRT-PCR, and western blotting. In vitro, RAW 264.7 macrophages were cultured under high glucose (33.3 mM) and treated with myricetin (12.5, 25, or 50 μM) for 24 h, with or without the PI3K/Akt inhibitor LY294002. Macrophage polarization was evaluated by flow cytometry (CD86/CD206), iNOS activity, and cytokine expression. Bioinformatics (SwissTargetPrediction, GeneCards, OMIM, STRING) and molecular docking (Autodock 4.2.6) identified potential targets and pathways.

**Key Results:** In db/db mice, myricetin (100 mg/kg) significantly reduced blood glucose, kidney/body weight ratio, serum creatinine, and uACR, and increased creatinine clearance (all P < 0.01 vs. db/db). Histological analysis showed reduced glomerular mesangial cell proliferation, capillary basement membrane thickening, and tubular vacuolation. KIM-1 and NGAL mRNA and protein levels were decreased. Myricetin reduced F4/80-positive macrophage infiltration, decreased M1 inflammatory cytokines (TNF-α, IL-6, IL-1β) at mRNA and protein levels, and increased M2 cytokine IL-10. Fibrosis markers Col1a1 and α-SMA were downregulated, and Masson's trichrome and Sirius-red staining showed reduced fibrosis. Flow cytometry revealed that myricetin decreased CD86+ (M1) and increased CD206+ (M2) macrophages in renal tissue. In vitro, high glucose (33.3 mM) induced M1 polarization of RAW 264.7 cells, with peak iNOS activity at 24 h. Myricetin (25 μM) significantly inhibited M1 polarization (M1 percentage 6.56% vs. 7.72% in control), reduced iNOS activity (P < 0.001), and decreased TNF-α, IL-6, IL-1β while increasing IL-10 and Arg-1. Bioinformatics identified 43 common targets between myricetin and DN, with Akt as a key hub. KEGG analysis highlighted the PI3K-Akt pathway. Molecular docking showed strong binding of myricetin to Akt (-6.31 kcal/mol) and PI3K (-8.31 kcal/mol). LY294002 (PI3K/Akt inhibitor) blocked myricetin's effects: it reversed the increase in CD206 and decrease in CD86, reduced Akt phosphorylation, and prevented the downregulation of M1 cytokines and upregulation of M2 markers.

**Clinical Implications:** This study demonstrates that myricetin ameliorates DN by promoting M2 macrophage polarization via the PI3K/Akt pathway, reducing inflammation and fibrosis. These findings provide a mechanistic basis for myricetin as a potential therapeutic agent for DN. However, clinical translation requires further studies, including human trials, to confirm efficacy and safety. The study also highlights the importance of targeting macrophage polarization in DN treatment.

PICO

PPOPULATION

Db/db diabetic mice (in vivo) and RAW 264.7 macrophages (in vitro)

IINTERVENTION

Myricetin (50 or 100 mg/kg intragastrically daily for 12 weeks in vivo; 25 μM for 24 h in vitro)

OOUTCOME

Kidney function (blood glucose, serum creatinine, uACR, creatinine clearance), renal histopathology (HE, PAS, Masson's trichrome, Sirius-red), kidney injury markers (KIM-1, NGAL), inflammatory cytokines (TNF-α, IL-6, IL-1β, IL-10), macrophage polarization markers (CD86, CD206, iNOS, Arg-1), fibrosis markers (Col1a1, α-SMA), and Akt phosphorylation

STUDY TYPE

other

SPECIALTY

nephrology

SUMMARISED BY

AI pipeline

FIDELITY CHECK

Not run

ORIGINAL PAPER

PMC10835493

Myricetin induces M2 macrophage polarization to alleviate renal tubulointerstitial fibrosis in diabetic nephropathy via PI3K/Akt pathway

World Journal of Diabetes

READ THE FULL PAPER

JUMP TO SECTION

ABSTRACT

BACKGROUND Development of end-stage renal disease is predominantly attributed to diabetic nephropathy (DN). Previous studies have indicated that myricetin possesses the potential to mitigate the pathological alterations observed in renal tissue. Nevertheless, the precise molecular mechanism through which myricetin influences the progression of DN remains uncertain. AIM To investigate the effects of myricetin on DN and explore its potential therapeutic mechanism. METHODS Db/db mice were administered myricetin intragastrically on a daily basis at doses of 50 mg/kg or 100 mg/kg for a duration of 12 wk. Subsequently, blood and urine indexes were assessed, along with examination of renal tissue pathology. Kidney morphology and fibrosis were evaluated using various staining techniques including hematoxylin and eosin, periodic acid–Schiff, Masson’s trichrome, and Sirius-red. Additionally, high-glucose culturing was conducted on the RAW 264.7 cell line, treated with 25 mM myricetin or co-administered with the PI3K/Akt inhibitor LY294002 for a period of 24 h. In both in vivo and in vitro settings, quantification of inflammation factor levels was conducted using western blotting, real-time qPCR and ELISA. RESULTS In db/db mice, administration of myricetin led to a mitigating effect on DN-induced renal dysfunction and fibrosis. Notably, we observed a significant reduction in expressions of the kidney injury markers kidney injury molecule-1 and neutrophil gelatinase associated lipocalin, along with a decrease in expressions of inflammatory cytokine-related factors. Furthermore, myricetin treatment effectively inhibited the up-regulation of tumor necrosis factor-alpha, interleukin-6, and interluekin-1β induced by high glucose in RAW 264.7 cells. Additionally, myricetin modulated the M1-type polarization of the RAW 264.7 cells. Molecular docking and bioinformatic analyses revealed Akt as the target of myricetin. The protective effect of myricetin was nullified upon blocking the polarization of RAW 264.7 via inhibition of PI3K/Akt activation using LY294002. CONCLUSION This study demonstrated that myricetin effectively mitigates kidney injury in DN mice through the regulation of macrophage polarization via the PI3K/Akt signaling pathway.

CITATION EXPORT

Wei-Long Xu, Pei-Pei Zhou, Xu Yu et al.. Myricetin induces M2 macrophage polarization to alleviate renal tubulointerstitial fibrosis in diabetic nephropathy via PI3K/Akt pathway. World Journal of Diabetes. (2024). https://doi.org/10.4239/wjd.v15.i1.105

AUTHORS

9 · 9 CENTRES

Wei-Long Xu, Pei-Pei Zhou, Xu Yu, Ting Tian, Jin-Jing Bao, Chang-Rong Ni, Min Zha, Xiao Wu, Jiang-Yi Yu

Department of Endocrinology, Jiangsu Province Hospital of Chinese Medicine, The Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210000, Jiangsu Province, China
Department of Endocrinology, Jiangsu Province Hospital of Chinese Medicine, The Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210000, Jiangsu Province, China
Department of Endocrinology, Jiangsu Province Hospital of Chinese Medicine, The Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210000, Jiangsu Province, China
Department of Endocrinology, Jiangsu Province Hospital of Chinese Medicine, The Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210000, Jiangsu Province, China
Department of Endocrinology, Jiangsu Province Hospital of Chinese Medicine, The Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210000, Jiangsu Province, China
Department of Pharmacy, Jiangsu Province Hospital of Chinese Medicine, The Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210000, Jiangsu Province, China
Department of Endocrinology, Jiangsu Province Hospital of Chinese Medicine, The Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210000, Jiangsu Province, China
Department of Pneumology, Jiangsu Province Hospital of Chinese Medicine, The Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210000, Jiangsu Province, China
Department of Endocrinology, Jiangsu Province Hospital of Chinese Medicine, The Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210000, Jiangsu Province, China. [email protected]