Polo-like kinase 1 (Plk1) is widely regarded as one of the most promising targets for cancer therapy due to its essential role in cell division and tumor cell survival. At present, most Plk1 inhibitors have been developed based on kinase domain, some of which are in clinical trial. However, inhibitors targeting kinase domain face off-target effect and drug resistance owing to the conserved nature and the frequent mutations in the ATP-binding pocket. In addition to a highly conserved kinase domain, Plk1 also contains a unique Polo-Box domain (PBD), which is essential for Plk1's subcellular localization and mitotic functions. Inhibitors targeting Plk1 PBD show stronger selectivity and less drug resistance for cancer therapy. Therefore, Plk1 PBD is an attractive target for the development of anti-cancer agents. In this review, we will summarize the up-to date drug discovery for targeting Plk1 PBD, including the molecular structure and cellular functions of Plk1 PBD. Small-molecule inhibitors targeting Plk1 PBD not only provide an opportunity to specifically inhibit Plk1 activity for cancer treatment, but also unveil novel biological basis regarding the molecular recognition of Plk1 and its substrates.
Cell Cycle Proteins/genetics* ; Neoplasms/drug therapy* ; Protein Kinase Inhibitors/pharmacology* ; Protein-Serine-Threonine Kinases/genetics* ; Proto-Oncogene Proteins/genetics*

This study aims to investigate the mechanism of Astragali Radix-Curcumae Rhizoma(HQEZ) in the treatment of gastric cancer based on network pharmacology. Further, the SGC7901 cell model of gastric cancer was employed to validate the efficacy and key targets of the herb pair. Firstly, the CCK-8 assay was employed to evaluate the direct effect of HQEZ on the proliferation of gastric cancer SGC7901 cells. Then, network pharmacology methods were employed to investigate the active ingredients, key targets, and key signaling pathways involved in the treatment of gastric cancer with HQEZ. The results showed that HQEZ contained 18 potential active ingredients, such as quercetin, naringenin, and curcumin. The results of gene ontology(GO) functional annotation and Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway enrichment suggested that the main targets of HQEZ in treating gastric cancer were involved in the regulation of protein serine/threonine kinase activity, activation of mitogen-activated protein kinase(MAPK) activity, cysteine-type endopeptidase activity, and negative regulation of protein serine/threonine kinase activity. The hypoxia-inducible factor-1(HIF-1) signaling pathway, ATP-binding cassette(ABC) transporters, cytochrome P450-mediated metabolism of xenobiotics, p53 signaling pathway, and cell apoptosis were key signaling pathways of HQEZ in treating gastric cancer. The cell experiments demonstrated that HQEZ significantly downregulated the expression of ATP-binding cassette subfamily B member 1(ABCB1), epidermal growth factor receptor(EGFR), phosphorylated serine/threonine kinase(p-AKT), hypoxia inducible factor 1 subunit alpha(HIF1A), B-cell lymphoma 2(BCL2), breast cancer susceptibility protein 1(BRCA1), DNA polymerase theta(POLH), ribonucleotide reductase M1(RRM1), and excision repair cross-complementation group 1(ERCC1), and upregulated the expression of tumor protein P53(TP53) and cysteinyl aspartate-specific proteinase(CAPS3). Finally, a multivariate COX regression model was adopted to study the relationship between gene expression and clinical information data of gastric cancer patients in the TCGA database, which demonstrated that the key targets of HQEZ were associated with the poor prognosis in gastric cancer patients. Further feature selection using the LASSO algorithm showed that EGFR, HIF1A, TP53, POLH, RRM1, and ERCC1 were closely associated with the survival of gastric can-cer patients. In conclusion, HQEZ regulates the expression of genes involved in DNA repair, survival, and apoptosis in gastric cancer cells via multiple targets and pathways, assisting the treatment of gastric cancer.
Humans ; Stomach Neoplasms/genetics* ; Tumor Suppressor Protein p53 ; Network Pharmacology ; ErbB Receptors ; Protein Serine-Threonine Kinases ; Serine ; Adenosine Triphosphate ; Molecular Docking Simulation ; Drugs, Chinese Herbal/pharmacology*

To explore the effect and mechanism of Dahuang Zhechong Pills(DHZCP), a classical prescription, in improving testicular aging(TA) in vivo, the authors randomly divided 24 male rats into four groups: the normal, model, DHZCP and vitamin E(VE) groups. The TA rat model was established by continuous gavage of D-galactose(D-gal). During the experiment, the rats in the DHZCP and VE groups were given DHZCP suspension and VE suspension, respectively by gavage, while those in the normal and model groups were gavaged saline separately every day. After the co-administration of D-gal and various drugs for 60 days, all rats were sacrificed, and their blood and testis were collected. Further, various indexes related to TA and necroptosis of testicular cells in the model rats were examined and investigated, which included the aging phenotype, total testicular weight, testicular index, histopathological features of testis, number of spermatogenic cells, sex hormone level, expression characteristics of reactive oxygen species(ROS) in testis, expression levels and characteristics of cyclins in testis, and protein expression levels of the key molecules in receptor-interacting serine/threonine-protein kinase 1(RIPK1)/receptor-interacting serine/threonine-protein kinase 3(RIPK3)/mixed lineage kinase domain like pseudokinase(MLKL) signaling pathway in each group. The results showed that, for the TA model rats, both DHZCP and VE improved their aging phenotype, total testicular weight, testicular index, pathological features of testis, number of spermatogenic cells, serum testosterone and follicle stimulating hormone levels, expression characteristics of ROS and protein expression levels and characteristics of P21 and P53 in testis. In addition, DHZCP and VE improved the protein expression levels of the key molecules in RIPK1/RIPK3/MLKL signaling pathway in testis of the model rats. Specifically, DHZCP was better than VE in the improvement of RIPK3. In conclusion, in this study, the authors found that DHZCP, similar to VE, ameliorated D-gal-induced TA in model rats in vivo, and its mechanism was related to reducing necroptosis of testicular cells by inhibiting the activation of RIPK1/RIPK3/MLKL signaling pathway. This study provided preliminary pharmacological evidence for the development and application of classical prescriptions in the field of men's health.
Aging ; Animals ; Drugs, Chinese Herbal ; Male ; Necroptosis ; Protein Kinases/genetics* ; Rats ; Reactive Oxygen Species/metabolism* ; Receptor-Interacting Protein Serine-Threonine Kinases/pharmacology* ; Serine/pharmacology* ; Signal Transduction ; Testis ; Threonine/pharmacology*

Antibody-mediated rejection (AMR) is one of the major causes of graft loss after transplantation. Recently, the regulation of B cell differentiation and the prevention of donor-specific antibody (DSA) production have gained increased attention in transplant research. Herein, we established a secondary allogeneic in vivo skin transplant model to study the effects of romidepsin (FK228) on DSA. The survival of grafted skins was monitored daily. The serum levels of DSA and the number of relevant immunocytes in the recipient spleens were evaluated by flow cytometry. Then, we isolated and purified B cells from B6 mouse spleens in vitro by magnetic bead sorting. The B cells were cultured with interleukin-4 (IL-4) and anti-clusters of differentiation 40 (CD40) antibody with or without FK228 treatment. The immunoglobulin G1 (IgG1) and IgM levels in the supernatant were evaluated by enzyme-linked immunosorbent assay (ELISA). Quantitative reverse transcription-polymerase chain reaction (RT-qPCR) and western blotting were conducted to determine the corresponding levels of messenger RNA (mRNA) and protein expression in cultured cells and the recipient spleens. The results showed that FK228 significantly improved the survival of allogeneic skin grafts. Moreover, FK228 inhibited DSA production in the serum along with the suppression of histone deacetylase 1 (HADC1) and HDAC2 and the upregulation of the acetylation of histones H2A and H3. It also inhibited the differentiation of B cells to plasma cells, decreased the transcription of positive regulatory domain-containing 1 (Prdm1) and X-box-binding protein 1 (Xbp1), and decreased the expression of phosphorylated inositol-requiring enzyme 1 α (p-IRE1α), XBP1, and B lymphocyte-induced maturation protein-1 (Blimp-1). In conclusion, FK228 could decrease the production of antibodies by B cells via inhibition of the IRE1α-XBP1 signaling pathway. Thus, FK228 is considered as a promising therapeutic agent for the clinical treatment of AMR.
Animals ; Depsipeptides ; Endoribonucleases ; Hematopoietic Stem Cell Transplantation ; Histone Deacetylase Inhibitors/pharmacology* ; Mice ; Protein Serine-Threonine Kinases ; Skin Transplantation

OBJECTIVE: To investigate the effect of metformin on the proliferation and apoptosis of HER-2-positive breast cancer cell line SKBR3 and explore the possible mechanism of its action. METHODS: SKBR3 cells were treated with different concentrations (20-120 μmol/L) of metformin, and the changes in cell proliferation and colony formation ability were assessed using CCK-8 assay and crystal violet staining, respectively. Flow cytometry was performed to analyze cell apoptosis and cell cycle changes. Real-time fluorescent quantitative PCR (qRT-PCR) was used to detect mRNA expressions of YAP, TAZ, EGFR, CTGF, CYR61, E-cadherin, N-cadherin, vimentin and fibronectin in the treated cells, and the protein expressions of YAP and TAZ were detected using Western blotting; immunofluorescence assay was used to observe YAP/TAZ nuclear translocation in the cells. RESULTS: Metformin treatment significantly inhibited the proliferation of SKBR3 cells (P < 0.05) in a concentration- and time-dependent manner. The results of flow cytometry showed that metformin significantly promoted apoptosis and caused cell cycle arrest at G1 phase in SKBR3 cells. Metformin treatment significantly down-regulated the mRNA expressions of YAP, TAZ, EGFR, CTGF and CYR61, N-cadherin, vimentin and fibronectin (P < 0.05) and up-regulated the expression of E-cadherin (P < 0.05); Western blotting results showed that YAP and TAZ protein expressions were significantly down-regulated in the cells after metformin treatment (P < 0.05). Immunofluorescence assay revealed that metformin treatment caused the concentration of YAP and TAZ in the cytoplasm, and significantly reduced their amount in the cell nucleus. CONCLUSION Metformin can inhibit proliferation and promote apoptosis and epithelal-mesenchymal transition of HER-2 positive breast cancer cells possibly by that inhibing YAP and TAZ expression and their nuclear localization.
Apoptosis ; Cadherins ; Cell Proliferation ; ErbB Receptors ; Fibronectins ; Metformin/pharmacology* ; Neoplasms ; Protein Serine-Threonine Kinases ; RNA, Messenger ; Transcription Factors/metabolism* ; Vimentin

The aim of this study was to observe whether necroptosis is involved in the process of cardiac hypertrophy induced by pressure overload. SD rats underwent transverse abdominal aortic constriction (TAC) operation for establishing cardiac hypertrophy model. The structure and function of the left ventricle of rats were evaluated via echocardiography, left ventricular mass index, the expression of markers of cardiac hypertrophy and histological detection. Real-time PCR and Western blot were used to measure the gene and protein expression of receptor interacting protein kinase 1 and 3 (RIPK1 and RIPK3, the necroptosis markers) respectively. Four weeks after TAC operation, rat model for cardiac hypertrophy was established. The experimental data showed that the gene and protein expressions of RIPK1 and RIPK3 in the rat heart hypertrophic tissues after TAC for 4 weeks were increased significantly compared with those in the sham group. HE staining showed cardiomyocytes injury and hypertrophy in the hearts of TAC rat models. By transmission electron microscope, we observed that mitochondria of cardiomyocytes were damaged seriously in the TAC models. Treatment with losartan used, the selective antagonist of angiotensin II type I receptor could improve the cardiac function of TAC rats. Moreover, losartan treatment decreased the expression of RIPK1 and RIPK3 in heart tissues of TAC rats. The results suggest that necroptosis occurrs in the process of cardiac hypertrophy with pressure overload, and losartan could alleviate the cardiac hypertrophy and inhibit necroptosis.
Animals ; Apoptosis ; Cardiomegaly ; pathology ; Disease Models, Animal ; Echocardiography ; Heart ; physiopathology ; Losartan ; pharmacology ; Myocytes, Cardiac ; Pressure ; Protein-Serine-Threonine Kinases ; metabolism ; Rats ; Rats, Sprague-Dawley ; Real-Time Polymerase Chain Reaction ; Receptor-Interacting Protein Serine-Threonine Kinases ; metabolism

OBJECTIVE: To investigate the effect of emodin on high glucose (HG)-induced podocyte apoptosis and whether the potential anti-apoptotic mechanism of emodin is related to induction of adenosine-monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR)-mediated autophagy in podocytes (MPC5 cells) in vitro. METHODS: MPC5 cells were treated with different concentrations of HG (2.5, 5, 10, 20, 40, 80 and 160 mmol/L), emodin (2, 4, 8 µ mol/L), or HG (40 mmol/L) and emodin (4 µ mol/L) with or without rapamycin (Rap, 100 nmol/L) and compound C (10 µ mol/L). The viability and apoptosis of MPC5 cells were detected using cell counting kit-8 (CCK-8) assay and flow cytometry analysis, respectively. The expression levels of cleaved caspase-3, autophagy marker light chain 3 (LC3) I/II, and AMPK/mTOR signaling pathway-related proteins were determined by Western blot. The changes of morphology and RFP-LC3 fluorescence were observed under microscopy. RESULTS: HG at 20, 40, 80 and 160 mmol/L dose-dependently induced cell apoptosis in MPC5 cells, whereas emodin (4 µ mol/L) significantly ameliorated HG-induced cell apoptosis and caspase-3 cleavage (P<0.01). Emodin (4 µ mol/L) significantly increased LC3-II protein expression levels and induced RFP-LC3-containing punctate structures in MPC5 cells (P<0.01). Furthermore, the protective effects of emodin were mimicked by rapamycin (100 nmol/L). Moreover, emodin increased the phosphorylation of AMPK and suppressed the phosphorylation of mTOR. The AMPK inhibitor compound C (10 µ mol/L) reversed emodin-induced autophagy activation. CONCLUSION Emodin ameliorated HG-induced apoptosis of MPC5 cells in vitro that involved induction of autophagy through the AMPK/mTOR signaling pathway, which might provide a potential therapeutic option for diabetic nephropathy.
Emodin/pharmacology* ; AMP-Activated Protein Kinases/metabolism* ; Podocytes ; Caspase 3/metabolism* ; TOR Serine-Threonine Kinases/metabolism* ; Signal Transduction ; Apoptosis ; Sirolimus/pharmacology* ; Glucose/metabolism* ; Autophagy

Previous studies have shown that high blood glucose-induced chronic microinflammation can cause inflammatory podocyte injury in patients with diabetic kidney disease(DKD). Therein, necroptosis is a new form of podocyte death that is closely associated with renal fibrosis(RF). To explore the effects and mechanisms in vivo of total flavones of Abelmoschus manihot(TFA), an extract from traditional Chinese herbal medicine Abelmoschus manihot for treating kidney diseases, on podocyte necroptosis and RF in DKD, and to further reveal its scientific connotation with multi-pathway and multi-target, the authors randomly divided all rats into four groups: a namely normal group, a model group, a TFA group and a rapamycin(RAP) group. After the modified DKD rat models were successfully established, four group rats were given double-distilled water, TFA suspension and RAP suspension, respectively by gavage every day. At the end of the 4th week of drug treatment, all rats were sacrificed, and the samples of their urine, blood and kidneys were collected. And then, the various indicators related to podocyte necroptosis and RF in the DKD model rats were observed, detected and analyzed, respectively. The results indicated that, general condition, body weight(BW), serum creatinine(Scr), urinary albumin(UAlb), and kidney hypertrophy index(KHI) in these modified DKD model rats were both improved by TFA and RAP. Indicators of RF, including glomerular histomorphological characteristics, fibronectin(FN) and collagen type Ⅰ(collagen Ⅰ) staining extent in glomeruli, as well as the protein expression levels of FN, collagen Ⅰ, transforming growth factor-β1(TGF-β1) and Smad2/3 in the kidneys were improved respectively by TFA and RAP. Podocyte damage, including foot process form and the protein expression levels of podocin and CD2AP in the kidneys was improved by TFA and RAP. In addition, tumor necrosis factor-α(TNF-α)-mediated podocyte necroptosis in the kidneys, including the morphological characteristics of podocyte necroptosis, the extent and levels of the protein expression of TNF-α and phosphorylated mixed lineage kinase domain like pseudokinase(p-MLKL) was improved respectively by TFA and RAP. Among them, RAP had the better effect on p-MLKL. More importantly, the activation of the receptor interacting serine/threonine protein kinase 1(RIPK1)/RIPK3/MLKL signaling axis in the kidneys, including the expression levels of its key signaling molecules, such as phosphorylated receptor interacting serine/threonine protein kinase 1(p-RIPK1), p-RIPK3, p-MLKL and cysteinyl aspartate specific proteinase-8(caspase-8) was improved respectively by TFA and RAP. Among them, the effect of TFA on p-RIPK1 was superior. On the whole, in this study, the authors demonstrated that TFA alleviates podocyte necroptosis and RF in DKD through inhibiting the activation of the TNF-α-mediated RIPK1/RIPK3/MLKL signaling axis in diabetic kidneys. The authors' findings provide new pharmacological evidence to reveal the scientific connotation of TFA in treating RF in DKD in more depth.
Humans ; Rats ; Animals ; Diabetic Nephropathies/drug therapy* ; Abelmoschus ; Flavones/pharmacology* ; Podocytes ; Tumor Necrosis Factor-alpha/metabolism* ; Necroptosis ; Receptor-Interacting Protein Serine-Threonine Kinases/metabolism* ; Fibrosis ; Threonine/pharmacology* ; Collagen/metabolism* ; Serine/pharmacology* ; Diabetes Mellitus/drug therapy*

OBJECTIVE: To explore the mechanism by which inositol-requiring enzyme-1α (IRE1α) regulates autophagy function of chondrocytes through calcium homeostasis endoplasmic reticulum protein (CHERP). METHODS: Cultured human chondrocytes (C28/I2 cells) were treated with tunicamycin, 4μ8c, rapamycin, or both 4μ8c and rapamycin, and the expressions of endoplasmic reticulum (ER) stress- and autophagy-related proteins were detected with Western blotting. Primary chondrocytes from ERN1 knockout (ERN1 CKO) mice and wild-type mice were examined for ATG5 and ATG7 mRNA expressions, IRE1α and p-IRE1α protein expressions, and intracellular calcium ion content using qPCR, Western blotting and flow cytometry. The effect of bafilomycin A1 treatment on LC3 Ⅱ/LC3 Ⅰ ratio in the isolated chondrocytes was assessed with Western blotting. Changes in autophagic flux of the chondrocytes in response to rapamycin treatment were detected using autophagy dual fluorescent virus. The changes in autophagy level in C28/I2 cells overexpressing CHERP and IRE1α were detected using immunofluorescence assay. RESULTS: Tunicamycin treatment significantly up-regulated ER stress-related proteins and LC3 Ⅱ/LC3 Ⅰ ratio and down-regulated the expression of p62 in C28/I2 cells (P < 0.05). Rapamycin obviously up-regulated LC3 Ⅱ/LC3 Ⅰ ratio (P < 0.001) in C28/I2 cells, but this effect was significantly attenuated by co-treatment with 4μ8c (P < 0.05). Compared with the cells from the wild-type mice, the primary chondrocytes from ERN1 knockout mice showed significantly down-regulated mRNA levels of ERN1 (P < 0.01), ATG5 (P < 0.001) and ATG7 (P < 0.001), lowered or even lost expressions of IRE1α and p-IRE1α proteins (PP < 0.01), and increased expression of CHERP (P < 0.05) and intracellular calcium ion content (P < 0.001). Bafilomycin A1 treatment obviously increased LC3 Ⅱ/ LC3 Ⅰ ratio in the chondrocytes from both wild-type and ERN1 knockout mice (P < 0.01 or 0.05), but the increment was more obvious in the wild-type chondrocytes (P < 0.05). Treatment with autophagy dual-fluorescence virus resulted in a significantly greater fluorescence intensity of LC3-GFP in rapamycin-treated ERN1 CKO chondrocytes than in wild-type chondrocytes (P < 0.05). In C28/I2 cells, overexpression of CHERP obviously decreased the fluorescence intensity of LC3, and overexpression of IRE1α enhanced the fluorescence intensity and partially rescued the fluorescence reduction of LC3 caused by CHERP. CONCLUSION IRE1α deficiency impairs autophagy in chondrocytes by upregulating CHERP and increasing intracellular calcium ion content.
Animals ; Autophagy ; Calcium/metabolism* ; Chondrocytes ; Endoplasmic Reticulum/metabolism* ; Endoribonucleases/pharmacology* ; Homeostasis ; Inositol ; Mice ; Mice, Knockout ; Protein Serine-Threonine Kinases ; RNA, Messenger/metabolism* ; Sirolimus/pharmacology* ; Tunicamycin/pharmacology*

OBJECTIVESTo explore the effects of insulin on the expression and the regulatory pathway of AQP9 in normal human liver cells.

METHODSNormal human liver cells L02 were cultured and treated with PI3K inhibitor LY294002, AKT inhibitor A-443654, MAPK inhibitors SB2030580 and insulin at different concentrations respectively. The AQP9 mRNA and protein expressions were detected with semi-quantitative RT-PCR and Western blot respectively.

RESULTSThe insulin (100 nmol/L approximately 500 nmol/L) treatment decreased the expression of AQP9 in normal human liver cells (P less than 0.05) concentration dependently, and the expression of AQP9 began to reduce from 3 hours of insulin stimulation (P less than 0.05), especially at insulin treatment for 12 hours (P less than 0.05); Incubated with the selective inhibitor of PI3K (LY294002) and AKT (A-443654), the inhibitory effects of insulin on AQP9 expression decreased (P less than 0.05); but it did not change significantly by blocking the MAPK signaling pathway.

CONCLUSIONThe insulin treatment inhibited the expression of AQP9 and the PI3K/akt signal transduction pathway was involved in the mechanism.

Aquaporins ; metabolism ; Cells, Cultured ; Chromones ; pharmacology ; Hepatocytes ; drug effects ; metabolism ; Humans ; Insulin ; pharmacology ; Morpholines ; pharmacology ; Phosphatidylinositol 3-Kinase ; antagonists & inhibitors ; metabolism ; Protein-Serine-Threonine Kinases ; metabolism ; Signal Transduction