Lycopene attenuates high glucose-mediated apoptosis in MPC5 podocytes by promoting autophagy via the PI3K/AKT signaling pathway

Carotenoids as modulators of the PI3K/Akt/mTOR pathway: innovative strategies in cancer therapy

Cancer progression is primarily driven by the uncontrolled activation of cellular signaling pathways, with the PI3K/Akt/mTOR (PAMT) pathway playing a central role. This pathway significantly contributes to the proliferation and survival of cancer cells, and its hyperactivity is a major challenge in managing several types of malignancies. This article delves into the promising potential of carotenoids, natural pigments found in abundance in fruits and vegetables, as a novel therapeutic strategy for cancer treatment. By specifically targeting and inhibiting the PAMT pathway, carotenoids may effectively disrupt the growth and survival of cancer cells. The article examines the complex mechanisms underlying these interactions and highlights the obstacles faced in cancer treatment. It proposes a compelling approach to developing therapies that leverage natural products to target this critical pathway, offering a fresh perspective on cancer treatment. Further research is essential to enhance the therapeutic efficacy of these compounds.

Insulin-like growth factor 1 knockdown attenuates high glucose-induced podocyte injury by promoting the JAK2/STAT signalling-mediated autophagy

PURPOSE

Podocyte injury plays a crucial role in the development of diabetic nephropathy (DN). A high serum level of insulin-like growth factor 1 (IGF-1) has been observed in patients with DN. This paper is to study the role and mechanism of IGF-1 in high glucose (HG)-induced podocyte injury.

METHODS

Mouse podocytes MPC-5 were treated with HG to establish a DN model in vitro. db/db diabetic mice and db/m nondiabetic mice were used to evaluate the IGF-1 role in vivo. Western blotting was used for measuring protein levels of IGF-1 receptor, Janus kinase/signal transducer and activator of transcription (JAK/STAT) signalling pathway-related markers, podocyte markers podocin and nephrin, apoptosis- and autophagy-related markers in MPC-5 cells. Immunofluorescence staining was implemented for measuring the expression of nephrin and the autophagy marker LC3. Flow cytometry was used for detecting podocyte apoptosis.

RESULTS

IGF-1 expression was increased in HG-stimulated MPC-5 cells and the kidney of db/db diabetic mice compared with corresponding controls. Knocking down IGF-1 downregulated IGF-1R and inhibited JAK2/STAT signalling pathway in HG-treated MPC-5 cells and db/db diabetic mice. IGF-1 silencing attenuated HG-induced podocyte injury, apoptosis and reduction in autophagy. Activating the JAK2/STAT signalling pathway or inhibiting autophagy reversed the effects of IGF-1 silencing on HG-treated MPC-5 cells.

CONCLUSION

Knocking down IGF-1 alleviates HG-induced podocyte injury and apoptosis by inactivating the JAK2/STAT signalling pathway and enhancing autophagy.

LYC inhibits the AKT signaling pathway to activate autophagy and ameliorate TGFB-induced renal fibrosis

Renal fibrosis is a typical pathological change in chronic kidney disease (CKD). Epithelial-mesenchymal transition (EMT) is the predominant stage. Activation of macroautophagy/autophagy plays a crucial role in the process of EMT. Lycopene (LYC) is a highly antioxidant carotenoid with pharmacological effects such as anti-inflammation, anti-apoptosis and mediation of autophagy. In this study, we demonstrated the specific mechanism of LYC in activating mitophagy and improving renal fibrosis. The enrichment analysis results of GO and KEGG showed that LYC had high enrichment values with autophagy. In this study, we showed that LYC alleviated aristolochic acid I (AAI)-induced intracellular expression of PINK1, TGFB/TGF-β, p-SMAD2, p-SMAD3, and PRKN/Parkin, recruited expression of MAP1LC3/LC3-II and SQSTM1/p62, decreased mitochondrial membrane potential (MMP), and ameliorated renal fibrosis in mice. When we simultaneously intervened NRK52E cells using bafilomycin A1 (Baf-A1), AAI, and LYC, intracellular MAP1LC3-II and SQSTM1 expression was significantly increased. A similar result was seen in renal tissue and cells when treated in vitro and in vivo with CQ, AAI, and LYC, and the inhibitory effect of LYC on the AAI-activated SMAD2-SMAD3 signaling pathway was attenuated. Molecular docking simulation experiments showed that LYC stably bound to the AKT active site. After intervention of cells with AAI and GSK-690693, the expression of PINK1, PRKN, MAP1LC3-II, BECN1, p-SMAD2 and p-SMAD3 was increased, and the expression of SQSTM1 was decreased. However, SC79 inhibited autophagy and reversed the inhibitory effect of LYC on EMT. The results showed that LYC could inhibit the AKT signaling pathway to activate mitophagy and reduce renal fibrosis.Abbreviation: AA: aristolochic acid; ACTA2/α-SMA: actin alpha 2, smooth muscle, aorta; ACTB: actin beta; AKT/protein kinase B: thymoma viral proto-oncogene; BAF-A1: bafilomycin A1; BECN1: beclin 1, autophagy related; CCN2/CTGF: cellular communication network factor 2; CDH1/E-Cadherin: cadherin 1; CKD: chronic kidney disease; COL1: collagen, type I; COL3: collagen, type III; CQ: chloroquine; ECM: extracellular matrix; EMT: epithelial-mesenchymal transition; FN1: fibronectin 1; LYC: lycopene; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MMP: mitochondrial membrane potential; MTOR: mechanistic target of rapamycin kinase ; PI3K: phosphoinositide 3-kinase; PINK1: PTEN induced putative kinase 1; PRKN/Parkin: parkin RBR E3 ubiquitin protein ligase; PPI: protein-protein interaction; SMAD2: SMAD family member 2; SMAD3: SMAD family member 3; SQSTM1/p62: sequestosome 1; TGFB/TGFβ: transforming growth factor, beta; VIM: vimentin.

Mutation of Beclin1 acetylation site at K414 alleviates high glucose-induced podocyte impairment in the early stage of diabetic nephropathy by inhibiting hyperactivated autophagy

BACKGROUND

Our group recently reported that a mutation of the novel Beclin1 K414R acetylation site impacts the stability of Beclin1 protein, which decreases autophagy in adipocytes and further impedes adipocyte differentiation and lipolysis. This study was to explore whether Beclin1 acetylation plays a role in the early renal injury induced by high glucose and to further investigate the K414R mutation site in podocytes.

METHODS

Male Sprague-Dawley rats were randomized to con (control) and diabetic nephropathy (DN) groups. The DN group was induced by a single 55 mg/kg intraperitoneal injection of streptozotocin and fed a high-fat and high-sugar diet (the con group received an equal volume of the vehicle and fed a plain diet), after 3 days of induction, blood glucose levels were measured to confirm the onset of diabetes. Then, at weeks 0 and 4, the biochemical index was assayed and renal cortex tissues were harvested. MPC5 podocytes were cultured in vitro. Beclin1 (K414R)-pLVX-ZsGreen1-N1(wild-type or mutant) lentiviral plasmids were transfected into podocytes. Western blot or immunoprecipitation was used to test proteins or the acetylation levels respectively, and immunohistochemistry was used to analyze morphological changes of podocytes. Immunofluorescence was used to detect the aggregation of LC3 puncta.

RESULTS

The acetylation level of Beclin1 was upregulated with podocyte injury exacerbated in high glucose at 24 h and that a mutation at K414R could inhibit hyperactivated autophagy, which ameliorated podocyte impairment.

CONCLUSION

These findings suggest that the acetylation site at K414 is a critical molecule and drug target and that further research into this area is warranted.

Fractalkine deficiency attenuates LPS-induced acute kidney injury and podocyte apoptosis by targeting the PI3K/Akt signal pathway

BACKGROUND

Podocyte injury is a major biomarker of primary glomerular disease, which leads to massive proteinuria and kidney failure. The increased production of the chemokine, fractalkine (FKN, CX3CL1), is a hallmark of multiple inflammatory diseases. However, the underlying mechanism of FKN in podocyte injury remains unknown.

METHODS

In this study, we performed an LPS infusion model in FKN knockout (FKN^-/-, FKN-KO) mice. In cultured podocytes, we used plasmids to knockdown FKN and treated the podocytes with PI3K/Akt inhibitor (LY294002). Haematoxylin and eosin (HE) staining, Western Bolt, Co-immunoprecipitation (Co-IP), Immunofluorescence staining and flow cytometric analysis were employed to establish the role of FKN in podocyte injury.

RESULTS

LPS stimulation resulted in kidney damage, increased the expression of the Bcl-2 family apoptosis protein, and decreased podocyte marker protein (nephrin, podocin and WT1) abundance compared with the WT mice. LPS-induced FKN-KO mice exhibited reduced lethality and inflammatory cell infiltration, podocyte apoptosis, and PI3K/Akt signal pathway inhibition compared to WT mice. In cultured podocytes, the interaction between FKN and the PI3K/Akt signalling pathway was well confirmed. FKN knockdown reduced podocyte apoptosis by regulating the Bcl-2 family; however, this protective effect was reversed by the co-administration of a PI3K/Akt inhibitor (LY294002).

CONCLUSION

Overall, these findings reveal a novel mechanistic property of FKN, PI3K/Akt signalling, and podocyte apoptosis.

Silencing of PFKFB3 protects podocytes against high glucose‑induced injury by inducing autophagy

Diabetic nephropathy (DN) is a diabetic complication that threatens the health of patients with diabetes. In addition, podocyte injury can lead to the occurrence of DN. The protein 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) may be associated with diabetes; however, the effects of PFKFB3 knockdown by small interfering (si)RNA on the growth of podocytes remains unknown. To investigate the mechanism by which PFKFB3 mediates podocyte injury, MPC5 mouse podocyte cells were treated with high-glucose (HG), and cell viability and apoptosis were examined by Cell Counting Kit-8 assay and flow cytometry, respectively. In addition, the expression of autophagy-related proteins were measured using western blot analysis and immunofluorescence staining. Cell migration was investigated using a Transwell assay and phalloidin staining was performed to observe the cytoskeleton. The results revealed that silencing of PFKFB3 significantly promoted MPC5 cell viability and inhibited apoptosis. In addition, the migration of the MPC5 cells was notably downregulated by siPFKFB3. Moreover, PFKFB3 silencing notably reversed the HG-induced decrease in oxygen consumption rate, and the HG-induced increase in extracellular acidification rate was rescued by PFKFB3 siRNA. Furthermore, silencing of PFKFB3 induced autophagy in HG-treated podocytes through inactivating phosphorylated (p-)mTOR, p-AMPKα, LC3 and sirtuin 1, and activating p62. In conclusion, silencing of PFKFB3 may protect podocytes from HG-induced injury by inducing autophagy. Therefore, PFKFB3 may serve as a potential target for treatment of DN.

Podocyte Autophagy in Homeostasis and Disease

Autophagy is a protective mechanism that removes dysfunctional components and provides nutrition for cells. Podocytes are terminally differentiated specialized epithelial cells that wrap around the capillaries of the glomerular filtration barrier and show high autophagy level at the baseline. Here, we provide an overview of cellular autophagy and its regulation in homeostasis with specific reference to podocytes. We discuss recent data that have focused on the functional role and regulation of autophagy during podocyte injury in experimental and clinical glomerular diseases. A thorough understanding of podocyte autophagy could shed novel insights into podocyte survival mechanisms with injury and offer potential targets for novel therapeutics for glomerular disease.