The coronavirus disease 2019 (COVID-19) pandemic has stimulated tremendous efforts to develop therapeutic agents that target severe acute respiratory syndrome coronavirus 2 to control viral infection. So far, a few small-molecule antiviral drugs, including nirmatrelvir-ritonavir (Paxlovid), remdesivir, and molnupiravir have been marketed for the treatment of COVID-19. Nirmatrelvir-ritonavir has been recommended by the World Health Organization as an early treatment for outpatients with mild-to-moderate COVID-19. However, the existing treatment options have limitations, and effective treatment strategies that are cost-effective and convenient for tackling COVID-19 are still needed. To date, four domestically developed oral anti-COVID-19 drugs have been granted conditional market approval in China. These drugs include azvudine, simnotrelvir-ritonavir (Xiannuoxin), leritrelvir, and mindeudesivir (VV116). Preclinical and clinical studies have explored the efficacy and tolerability of mindeudesivir and supported its early use in mild-to-moderate COVID-19 cases at high risk for progression. In this review, we discuss the most recent findings regarding the pharmacological mechanism and therapeutic effects focusing on mindeudesivir and other small-molecule antiviral agents for COVID-19. These findings will expand our understanding and highlight the potential widespread application of China's homegrown anti-COVID-19 drugs.
Humans ; Ritonavir/therapeutic use* ; COVID-19 ; Antiviral Agents/therapeutic use* ; China ; Nitriles ; Lactams ; Proline ; Adenosine/analogs & derivatives* ; Leucine

BACKGROUND: The objective of this study was to evaluate the role of proteases on the degradation of parathyroid hormone (PTH) in blood samples. METHODS: Protease inhibitors with specificity against serine proteases (aprotinin), cysteine proteases (E-64), serine and cysteine proteases (leupeptin), metalloproteases (EDTA), or a protease inhibitor cocktail with a broad spectrum of inhibitory activity were added to blood samples. After storage at room temperature (0-48 hr), PTH levels were measured. RESULTS: PTH levels in samples with the protease inhibitor cocktail did not change significantly after 48 hr of storage at room temperature, but the average PTH levels decreased by 40.7% and 20.1%, in samples stored at room temperature and stored at 4degrees C without protease inhibitors, respectively. PTH levels in samples with leupeptin were stable for up to 24 hr. After 48 hr, the mean PTH levels decreased by 17.1%, 16.0%, 26.2%, and 32.1%, with 500 KIU/mL aprotinin, 100 micro mol/L leupeptin, 10 micro mol/L E-64, and 10 micro mol/L EDTA, respectively, in the samples stored at room temperature. CONCLUSIONS: The decrease in PTH levels in blood samples seemed to be due to the degradation of PTH by proteases. Various proteases, including especially serine proteases, would act together to degrade PTH in blood specimen. The PTH degradation may be inhibited in blood specimen with protease inhibitor cocktail.
Aprotinin/pharmacology ; Blood Specimen Collection ; Edetic Acid/pharmacology ; Female ; Humans ; Leucine/analogs & derivatives/pharmacology ; Leupeptins/pharmacology ; Male ; Parathyroid Hormone/*blood/metabolism ; Protease Inhibitors/*pharmacology ; Time Factors

OBJECTIVETo investigate the effect of aminopeptidase N inhibitor ubenimex on differentiation induction of all-trans-retinoic acid (ATRA) in acute promyelocytic leukemia (APL) cells and its mechanism.

METHODSThe expression of CD11b was analyzed by flow cytometry and nitroblue-tetrazolium (NBT) reduction assay was performed to determine the cell differentiation of APL cells. The expressions of c-Myc, ERK1/2, p38MAPK protein and the phosphorylation of ERK1/2, p38MAPK protein in NB4 cells were detected by Western blot assay.

RESULTSUbenimex alone induced no significant changes in NBT reduction activity and CD11b expression but potentiated the differentiation induction activity of ATRA in APL cells. 100 microg/ml of ubenimex could enhance the NBT reduction activity induced by 10 nmol/L of ATRA, intensify the down-regulation of c-Myc protein expression and inhibit the phosphorylation of p38MAPK protein induced by 10 nmol/L of ATRA in NB4 cells.

CONCLUSIONSUbenimex could potentiate ATRA induced differentiation in APL cells, which may be correlated with the inhibition of p38 MAPK protein phosphorylation and regulation of c-Myc protein expression.

Aminopeptidases ; antagonists & inhibitors ; Cell Differentiation ; drug effects ; Drug Synergism ; Flow Cytometry ; Humans ; In Vitro Techniques ; Leucine ; analogs & derivatives ; pharmacology ; Leukemia, Promyelocytic, Acute ; pathology ; Tretinoin ; pharmacology

A 29 kDa cysteine protease of Taenia solium metacestodes was purified by Mono Q anion-exchanger and Superose 6 HR gel filtration chromatography. The enzyme was effectively inhibited by cysteine protease inhibitors, such as iodoacetic acid (IAA) and trans-epoxy-succinyl-L-leucyl-amido (4-guanidino) butane (E-64) while inhibitors acting on serine- or metallo-proteases did not affect the enzyme activity. The purified enzyme degraded human immunoglobulin G (IgG), collagen and bovine serum albumin (BSA), but human IgG was more susceptible for proteolysis by the enzyme. To define the precise biological roles of the enzyme, more detailed biochemical and functional studies would be required.
Taenia solium/*enzymology ; Serum Albumin, Bovine/metabolism ; Leucine/analogs & derivatives/pharmacology ; Iodoacetic Acid/pharmacology ; Immunoglobulin G/metabolism ; Humans ; Cysteine Proteinase Inhibitors/pharmacology ; Cysteine Endopeptidases/chemistry/*isolation & purification/metabolism ; Collagen/metabolism ; Chromatography, Ion Exchange ; Chromatography, Gel ; Animals

This study was purposed to investigate whether aminopeptidase inhibitor, bestatin, can potentiate all-trans retinoic acid (ATRA)-inducing differentiation in NB4 cells, and to explore its mechanism. The NB4 cells were exposed to either bestatin and ATRA alone or in combination, the morphological changes of NB4 cells were observed by optical microscopy, the CD11b expression was measured by flow cytometry, the function of defferentiation cells was analyzed by nitroblue-tetrazolium (NBT) reduction assay, the mRNA expressions of c-myc and c-EBPepsilon in NB4 cells were detected by RT-PCR, the c-Myc protein expression was determined by Western blot. The results showed that treatment with bestatin alone induced no significant changes in morphology, NBT reduction activity and CD11b expression in NB4 cells. NB4 cells incubated with 10 nmol/L ATRA plus 100 microg/ml bestatin showed more morphologic feature of metamyelocyte and band neutrophil than ATRA alone treated cells. 100 microg/ml bestatin enhanced the NBT reduction activity in NB4 cells induced by various concentrations of ATRA (10, 20, 40 nmol/L). The effects of various concentrations of ATRA in combination with 100 microg/ml bestatin were statistically different from the effect of ATRA alone (P < 0.01). From 48 to 96 hours, 100 microg/ml bestatin time-dependently increased NBT reduction in NB4 cells induced by 10 nmol/L ATRA (P < 0.01). 10 nmol/L ATRA plus 100 microg/ml bestatin for 72 hours prominently elevated CD11b expression in NB4 cells as compared with ATRA alone treated NB4 cells (P < 0.01). There was a substantial decrease in c-myc mRNA levels when 100 microg/ml bestatin was added to 10 nmol/L ATRA (P < 0.05). Various concentrations (50, 75, 100 microg/ml) of bestatin combined with 10 nmol/L ATRA down-regulated the expression of c-Myc protein, which was negatively correlated with the NBT reduction activity of NB4 cells induced by 10 nmol/L ATRA alone or plus bestatin at various concentrations (r = -0.940, P = 0.017). However, 100 microg/ml bestatin plus 10 nmol/L ATRA could not induce any significant changes in the levels of c-EBPepsilon mRNA as compared with ATRA alone treated NB4 cells. It is concluded that an aminopeptidase inhibitor bestatin can potentiate ATRA-inducing differentiation of NB4 cells, possibly by down-regulating c-myc expression in synergy with ATRA.
Aminopeptidases ; antagonists & inhibitors ; Antibiotics, Antineoplastic ; pharmacology ; Cell Transformation, Neoplastic ; drug effects ; Down-Regulation ; Drug Synergism ; Humans ; Leucine ; analogs & derivatives ; pharmacology ; Leukemia, Promyelocytic, Acute ; pathology ; Proto-Oncogene Proteins c-myc ; drug effects ; metabolism ; Tretinoin ; pharmacology ; Tumor Cells, Cultured

This study was purposed to investigate the effect of aminopeptidase N/CD13 on bestatin enhancing all-trans-retinoic acid (ATRA)-inducing differentiation in NB4 cells. The nitroblue-tetrazolium (NBT) reduction assay was performed to determine the differentiation of NB4 cells, MR2 cells and primary APL blasts. The expression of P38 MAPK protein and the phosphorylation of P38 MAPK protein in NB4, MR2 and K562 cells were detected by Western blot. The results showed that pre-incubation with 5 µg/ml WM-15 blocked the enhancement effect of bestatin on differentiation of NB4 cells induced by ATRA. 5 µg/ml CD13 antibody WM-15 partly blocked the inhibition of bestatin on the phosphorylation of P38 MAPK in NB4 cells. 100 µg/ml bestatin inhibited the phosphorylation of P38 MAPK in NB4 cells and MR2 cells in a time-dependent manner. 100 µg/ml bestatin had no effect on the phosphorylation of P38 MAPK in K562 cells with low level of CD13. Bestatin could not restore the sensitivity to ATRA in ATRA-resistant primary APL blasts and MR2 cells. It is concluded that aminopeptidase N/CD13 inhibitor bestatin may enhance the differentiation-inducing activity of ATRA through inhibiting the phosphorylation of P38 MAPK in NB4 cells mediated by the cell surface APN/CD13.
Antibiotics, Antineoplastic ; pharmacology ; Antineoplastic Agents ; CD13 Antigens ; antagonists & inhibitors ; metabolism ; Cell Differentiation ; drug effects ; Cell Division ; drug effects ; Cell Line, Tumor ; Humans ; Leucine ; analogs & derivatives ; pharmacology ; Leukemia, Promyelocytic, Acute ; metabolism ; pathology ; Phosphorylation ; Tretinoin ; p38 Mitogen-Activated Protein Kinases ; metabolism

OBJECTIVETo investigate the effect of DADLE, a δ-opioid receptor agonist, on the proliferation of human liver cancer HepG2 cells and explore the mechanism involving PKC pathway.

METHODSHepG2 cells were treated with DADLE at different doses (0.01, 0.1, 1.0 and 10 µmol/L). Cell viability was determined using methyl thiazolyl terazolium (MTT) assay. The expression of PKC mRNA and p-PKC protein were examined by RT-PCR and Western blot assay. After treated separately with DADLE plusing NAL or PMA, the cell cycle of HepG2 cells was analyzed by flow cytometer. MTT was used to detect their proliferation capacity and Western blot was used to examine the p-PKC expression. The growth inhibitory rate of HepG2 cells treated with DADLE and cis-diammine dichloridoplatinum (CDDP) was analyzed.

RESULTSDADLE at different concentrations showed an inhibitory effect on the proliferation of HepG2 cells though inhibiting the expression of PKC mRNA and p-PKC protein. The results of flow cytometry showed that compared with the control group, the percentage of S + G(2)/M cells in DADLE-treated group was lowered by 3.94% (P < 0.01). Meanwhile, after treated with NAL and PMA, the percentage was elevated by 3.22% and 3.63%, respectively (P < 0.01). The MTT and Western blot assays showed that compared with the control group, the values of A570 and p-PKC protein levels in the HepG2 cells of DADLE-treated group were significantly decreased (P < 0.01). After treatment with NAL and PMA, the values of A570 and p-PKC protein levels were elevated significantly (P < 0.01). The growth inhibitory rate of DADLE + CDDP group was 79.9%, significantly lower than 25.2% and 43.2% of the DADLE and CDDP groups, respectively.

CONCLUSIONSActivation of δ-opioid receptor by DADLE inhibits the apoptosis of human liver cancer HepG2 cells. The underlying mechanism may be correlated with PKC pathway. DADLE can enhance the chemosensitivity of HepG2 cells to CDDP.

Antineoplastic Agents ; pharmacology ; Cell Cycle ; drug effects ; Cell Proliferation ; drug effects ; Cisplatin ; pharmacology ; Dose-Response Relationship, Drug ; Drug Resistance, Neoplasm ; Enkephalin, Leucine-2-Alanine ; administration & dosage ; pharmacology ; Hep G2 Cells ; Humans ; Naltrexone ; analogs & derivatives ; pharmacology ; Phosphorylation ; Protein Kinase C ; genetics ; metabolism ; RNA, Messenger ; metabolism ; Receptors, Opioid, delta ; agonists ; Signal Transduction ; Tetradecanoylphorbol Acetate ; analogs & derivatives ; pharmacology

Glioma stem/progenitor cells (GSPCs) are considered to be responsible for the initiation, propagation, and recurrence of gliomas. The factors determining their differentiation remain poorly defined. Accumulating evidences indicate that alterations in autophagy may influence cell fate during mammalian development and differentiation. Here, we investigated the role of autophagy in GSPC differentiation. SU-2 cells were treated with rapamycin, 3-methyladenine (3-MA) plus rapamycin, E64d plus rapamycin, or untreated as control. SU-2 cell xenografts in nude mice were treated with rapamycin or 3-MA plus rapamycin, or untreated as control. Western blotting and immunocytochemistry showed up-regulation of microtubule-associated protein light chain-3 (LC3)-II in rapamycin-treated cells. The neurosphere formation rate and the number of cells in each neurosphere were significantly lower in the rapamycin treatment group than in other groups. Real-time PCR and immunocytochemistry showed down-regulation of stem/progenitor cell markers and up-regulation of differentiation markers in rapamycin-treated cells. Transmission electron microscopy revealed autophagy activation in rapamycin-treated tumor cells in mice. Immunohistochemistry revealed decreased Nestin-positive cells and increased GFAP-positive cells in rapamycin-treated tumor sections. These results indicate that rapamycin induces differentiation of GSPCs by activating autophagy.
Adenine ; analogs & derivatives ; pharmacology ; Animals ; Antibiotics, Antineoplastic ; pharmacology ; Autophagy ; drug effects ; Brain Neoplasms ; metabolism ; pathology ; Cell Differentiation ; drug effects ; Cell Line, Tumor ; Female ; Glial Fibrillary Acidic Protein ; genetics ; metabolism ; Glioma ; metabolism ; pathology ; Humans ; Leucine ; analogs & derivatives ; pharmacology ; Male ; Mice ; Mice, Inbred BALB C ; Mice, Nude ; Microtubule-Associated Proteins ; metabolism ; Neoplastic Stem Cells ; pathology ; RNA, Messenger ; metabolism ; Sirolimus ; pharmacology ; Xenograft Model Antitumor Assays

Because of the complexity of the cathepsin B-like (CBL) family, an information on the biological and biochemical characteristics of individual CBL genes is lacking. In this study, we investigated the degradative effects of the recombinant HC58 protein isolated from Haemonchus contortus parasites on protein substrates over a broad pH range in vitro. This protein, which hydrolyzed the synthetic peptide substrates Z-FR-AMC and Z-RR-AMC, had characteristics of the cysteine protease class of proteins. In the acidic pH range, the isolated protein actively degraded hemoglobin (Hb), the heavy chain of goat immunoglobulin G, and azocasein. By contrast, it degraded fibrinogen in the alkaline pH range. These activities were strongly inhibited in the presence of the cysteine protease inhibitor E-64. While the protein digested Hb, it did not induce the agglutination of erythrocytes from its natural host. These results suggest that the HC58 protein may play a role in the nutrition of this parasite.
Animals ; Caseins/metabolism ; Cathepsin B/antagonists&inhibitors/*genetics/isolation & purification/*metabolism ; Cysteine Proteinase Inhibitors/pharmacology ; DNA, Complementary/genetics ; Goat Diseases/*parasitology ; Goats ; Haemonchiasis/parasitology/*veterinary ; Haemonchus/*enzymology/genetics/isolation & purification ; Hemagglutination Tests/veterinary ; Hemoglobins/metabolism ; Hydrogen-Ion Concentration ; Immunoglobulin G/metabolism ; Leucine/analogs & derivatives/pharmacology ; RNA, Helminth/chemistry/genetics ; Recombinant Proteins/genetics/metabolism ; Reverse Transcriptase Polymerase Chain Reaction/veterinary

This study is to investigate the effects of ubenimex on tumor cell invasion and apoptosis, dose relationship and mechanism. Immunofluorescence staining was performed to detect the expression of CD13 in HT-1080 cells. MTT assay was used to analyze the effect of ubenimex on cell proliferation. Annexin V-EGFP/PI was used to detect apoptotic cells by flow cytometry. Cell cycle was analyzed using flow cytometry. Ala-pNA was used as substrate to evaluate the effect of ubenimex on the aminopeptidase activity. Transwell assay was used to analyze the effect of ubenimex on cell invasion and migration ability. Western blotting was used to detect the expression level of CD13. MMP activity was analyzed using gelatin zymography. The results showed that ubenimex at high concentration inhibited the proliferation of HT-1080 cells (IC50: 3.8 mg x mL(-1)), and induced cell apoptosis. Cell cycle was blocked at G1 phase. Ubenimex at low concentration inhibited the aminopeptidase activity of HT-1080 cells (IC50: 8.3 microg x mL(-1)) and inhibited cell invasion, but it had no effects on the cell migration and proliferation. Ubenimex had no effects on CD13 expression and MMP activity. In conclusion, ubenimex at low concentration can inhibit the invasion ability of tumor cells by directly inhibiting the aminopeptidase activity; ubenimex at high concentration can inhibit the proliferation of tumor cells and induce cell apoptosis by a CD13-independent pathway.
Antibiotics, Antineoplastic ; pharmacology ; Apoptosis ; drug effects ; CD13 Antigens ; metabolism ; Cell Cycle ; drug effects ; Cell Line, Tumor ; Cell Movement ; drug effects ; Cell Proliferation ; drug effects ; Fibrosarcoma ; metabolism ; pathology ; Humans ; Leucine ; analogs & derivatives ; pharmacology ; Matrix Metalloproteinase 2 ; metabolism ; Matrix Metalloproteinase 9 ; metabolism ; Neoplasm Invasiveness