Structural Understanding of Peptide-Bound G Protein-Coupled Receptors: Peptide-Target Interactions.

The activation of G protein-coupled receptors (GPCRs) is triggered by ligand binding to their orthosteric sites, which induces ligand-specific conformational changes. Agonists and antagonists bound to GPCR orthosteric sites provide detailed information on ligand-binding modes. Among these, peptide ligands play an instrumental role in GPCR pharmacology and have attracted increased attention as therapeutic drugs. The recent breakthrough in GPCR structural biology has resulted in the remarkable availability of peptide-bound GPCR complexes. Despite the several structural similarities shared by these receptors, they exhibit distinct features in terms of peptide recognition and receptor activation. From this perspective, we have summarized the current status of peptide-bound GPCR structural complexes, largely focusing on the interactions between the receptor and its peptide ligand at the orthosteric site. In-depth structural investigations have yielded valuable insights into the molecular mechanisms underlying peptide recognition. This study would contribute to the discovery of GPCR peptide drugs with improved therapeutic effects.

Exploring Cantharidin and its Analogues as Anticancer Agents: A Review.

BACKGROUND: Cantharidin (CTD) is a highly toxic substance which can be used to treat a variety of cancers. However, the clinical application of CTD is restricted due to the serious side effects. In recent years, screening its analogues, exploring the mechanism of action and using combinatory therapy with certain substances are considered to be feasible methods which can reduce side effects and improve the therapeutic activity of CTD. This review aims to describe SAR (structure-activity relationship) of CTD analogues, CTD induction mechanisms, and combinatory therapy exploration. METHODS: We searched for research about CTD by entering the database. Important information was screened and extracted purposefully, including SAR, mechanisms, methods, etc. Finally, these contents were unified into a framework to form a review. RESULTS: Some CTD analogues with imidazolium salt or double bonds at C-5 and C-6 positions demonstrate good anticancer activity. Through introducing methyl and acetoxy groups at the C-1 or C-4 position, the inhibitory effect of PP was weakened or even inactivated. Removing the two methyl groups of C-2 and C-3 can reduce side effects and improve efficacy. Replacing methyl with fluorine can also improve the activity and reduce toxicity. Water solubility and bioavailability could be improved by opening the five fivemembered anhydride ring to form carboxylic acid, salt, amide, and ester derivatives. The anticancer mechanism can be divided into the following aspects, including inhibiting cell invasion and metastasis, inducing apoptosis, regulating cell cycle and enhancing immunity. The proper formulation of CTD and its analogues (liposomes, nanoparticles and micelles) can improve the targeting of liver cancer and reduce toxic and side effects. CTD combined with anti-angiogenic therapeutics (Ginsenoside Rg3, Bevacizumab, Apatinib and Endostar) showed additive anti-pancreatic cancer effects. CONCLUSION: It was found that the potential mechanism was closely related to multi-channel and multi-target interactions, which provided a guiding direction for the later exploration of new clinical therapeutic applications. However, some detailed mechanisms are still unclear, and more evidence is required to verify. In addition, the new methods to improve the therapeutic potential of CTD and its analogues still need more clinical trials to be tested in the future. This prospect is very broad and worthy of further study.

Mechanistic Insights Into Co-Administration of Allosteric and Orthosteric Drugs to Overcome Drug-Resistance in T315I BCR-ABL1.

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm, driven by the BCR-ABL1 fusion oncoprotein. The discovery of orthosteric BCR-ABL1 tyrosine kinase inhibitors (TKIs) targeting its active ATP-binding pocket, such as first-generation Imatinib and second-generation Nilotinib (NIL), has profoundly revolutionized the therapeutic landscape of CML. However, currently targeted therapeutics still face considerable challenges with the inevitable emergence of drug-resistant mutations within BCR-ABL1. One of the most common resistant mutations in BCR-ABL1 is the T315I gatekeeper mutation, which confers resistance to most current TKIs in use. To resolve such conundrum, co-administration of orthosteric TKIs and allosteric drugs offers a novel paradigm to tackle drug resistance. Remarkably, previous studies have confirmed that the dual targeting BCR-ABL1 utilizing orthosteric TKI NIL and allosteric inhibitor ABL001 resulted in eradication of the CML xenograft tumors, exhibiting promising therapeutic potential. Previous studies have demonstrated the cooperated mechanism of two drugs. However, the conformational landscapes of synergistic effects remain unclear, hampering future efforts in optimizations and improvements. Hence, extensive large-scale molecular dynamics (MD) simulations of wide type (WT), WT-NIL, T315I, T315I-NIL, T315I-ABL001 and T315I-ABL001-NIL systems were carried out in an attempt to address such question. Simulation data revealed that the dynamic landscape of NIL-bound BCR-ABL1 was significantly reshaped upon ABL001 binding, as it shifted from an active conformation towards an inactive conformation. The community network of allosteric signaling was analyzed to elucidate the atomistic overview of allosteric regulation within BCR-ABL1. Moreover, binding free energy analysis unveiled that the affinity of NIL to BCR-ABL1 increased by the induction of ABL001, which led to its favorable binding and the release of drug resistance. The findings uncovered the in-depth structural mechanisms underpinning dual-targeting towards T315I BCR-ABL1 to overcome its drug resistance and will offer guidance for the rational design of next generations of BCR-ABL1 modulators and future combinatory therapeutic regimens.

Ultrasound-Assisted Extraction, Identification, and Quantification of Antioxidants from 'Jinfeng' Kiwifruit.

Kiwifruit (Actinidia chinensis) is a nutrient-dense fruit abundant in vitamin C and phenolic compounds, and it exhibits strong antioxidant capacity. However, the antioxidants in 'Jinfeng' kiwifruit have seldom been extracted and analyzed, and the conditions for the extraction of kiwifruit antioxidants by ultrasound-assisted extraction (UAE) have seldom been investigated. In this study, response surface methodology (RSM) was used to optimize UAE conditions to extract antioxidants from 'Jinfeng' kiwifruit. In addition, the antioxidant capacity, contents of total phenolics and total flavonoids, ascorbic acid, and the profiles of antioxidants were also analyzed. The results showed that the optimal UAE conditions included 68% ethanol, liquid/solid ratio at 20 mL/g, extraction time at 30 min, extraction temperature at 42 °C, and ultrasonic power at 420 W. Under these conditions, the ABTS value of kiwifruit was 70.38 ± 1.38 µM TE/g DW, which was 18.5% higher than that of the extract obtained by conventional solvent extraction. The total phenolic and flavonoid contents were 15.50 ± 0.08 mg GAE/g DW and 5.10 ± 0.09 mg CE/g DW, respectively. Moreover, 20 compounds were tentatively identified by UPLC-MS/MS, and the content of main compounds, such as procyanidin B2, neochlorogenic acid, and epicatechin, were determined by HPLC-DAD. This research revealed the profiles of antioxidant phytochemicals in 'Jinfeng' kiwifruit, which can be a good dietary source of natural antioxidants with potential health functions.

Therapeutic potential of phosphodiesterase inhibitors for cognitive amelioration in Alzheimer's disease.

Alzheimer's disease (AD), one of the greatest threats to human health, is characterized by declined cognition and changed behavior. Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) that play an important role in learning and memory are hydrolyzed by phosphodiesterases (PDEs). Most PDE isoforms are highly expressed in the brain, and the inhibition of PDEs is beneficial to counteract AD. Thus, targeting PDEs represents a therapeutic potential for this disease. So far, a variety of PDE inhibitors have been discovered with significant cognitive enhancement effects in animal models and more than ten agents have entered into clinical trials. In this review, we summarize PDE mediated cyclic nucleotide signaling pathways, PDE family members involved in AD and recent advance of PDE inhibitors in preclinical and clinical studies, trying to provide an outlook of PDE inhibitors for the treatment of AD in future.

High Blood Cytomegalovirus Load Suggests Cytomegalovirus Retinitis in HIV/AIDS Patients: A Cross-Sectional Study.

PURPOSE: To clarify the cut off value of blood CMV load to indicate CMV retinitis and its relationships with ocular features. METHODS: Patients were divided into non-CMV and CMV retinitis groups. A logistic regression model was applied to estimate the association of each variable with CMV retinitis. Spearman correlation was used to estimate the correlation between the blood and aqueous CMV load. RESULTS: Blood CMV load higher than 4log10 (OR, 6.897; CI: 2.813-16.910; P < .001) was the major predictor of CMV retinitis. Blood CMV load wasn't different between the initial and early stage (P = .066). No correlation was observed between the blood and aqueous CMV load (P = .083, r = 0.228). CONCLUSIONS: Blood CMV load higher than 4log10 is an important predictor for CMV retinitis in HIV/AIDS patients, but it couldn't indicate the ocular features. Ophthalmologic screening is still necessary.Abbreviations: CMV: Cytomegalovirus; CMVR: Cytomegalovirus retinitis; HIV: Human Immunodeficiency Virus; AIDS: Acquired Immune Deficiency Syndrome; ART: Antiretroviral therapy; EOD: End-organ diseases; PCR: Polymerase Chain Reaction; OR: Odds Ratio; CI: 95% Confidence Interval; IQR: Interquartile range.

Ethylene response factor AcERF91 affects ascorbate metabolism via regulation of GDP-galactose phosphorylase encoding gene (AcGGP3) in kiwifruit.

Kiwifruit is known as 'the king of vitamin C' because of the high content of ascorbic acid (AsA) in the fruit. Deciphering the regulatory network and identification of the key regulators mediating AsA biosynthesis is vital for fruit nutrition and quality improvement. To date, however, the key transcription factors regulating AsA metabolism during kiwifruit developmental and ripening processes remains largely unknown. Here, we generated a putative transcriptional regulatory network mediating ascorbate metabolism by transcriptome co-expression analysis. Further studies identified an ethylene response factor AcERF91 from this regulatory network, which is highly co-expressed with a GDP-galactose phosphorylase encoding gene (AcGGP3) during fruit developmental and ripening processes. Through dual-luciferase reporter and yeast one-hybrid assays, it was shown that AcERF91 is able to bind and directly activate the activity of the AcGGP3 promoter. Furthermore, transient expression of AcERF91 in kiwifruit fruits resulted in a significant increase in AsA content and AcGGP3 transcript level, indicating a positive role of AcERF91 in controlling AsA accumulation via regulation of the expression of AcGGP3. Overall, our results provide a new insight into the regulation of AsA metabolism in kiwifruit.

Clinical efficacy of laser therapy in the prevention of retinal detachment in patients with acquired immunodeficiency syndrome and cytomegalovirus retinitis.

BACKGROUND: The aim of the present study was to evaluate the clinical efficacy of laser therapy in the prevention of retinal detachment in patients with acquired immunodeficiency syndrome (AIDS) and cytomegalovirus retinitis (CMVR). METHODS: A total of 96 eyes from 80 patients with AIDS and CMVR who received anticytomegalovirus (anti-CMV) treatment in the ophthalmology and infection centers of Beijing YouAn Hospital, between June 2016 and August 2018 were retrospectively investigated. The patients were randomly divided into a nonlaser group (50 eyes from 43 patients), who were treated with anti-CMV therapy, and a laser group (46 eyes from 37 patients), who were treated with a fundus laser method to close the retinopathy area after commencing the maintenance stage of anti-CMV treatment. Both groups were followed up for 24 months. The safety of laser therapy was observed, and the efficacy of the therapy was determined by evaluating the incidence of retinal detachment. RESULTS: The percentage of retinal detachment in the nonlaser group was 24% compared with 6.5% in the laser group (P=0.018). There was no significant difference between the two groups in the number of CD4+ T cells, the load of human immunodeficiency virus, or the time between the detachment and the end of the induction period. After laser therapy, 39.13% of patients exhibited keratic precipitates (KP), 30.43% had anterior chamber flare (±), 50% had anterior chamber flare (+), and 19.57% had anterior chamber flare (++). Intraocular pressure (IOP) increased in 3 eyes within 2 weeks of laser therapy. The retinal pigment reaction was not obvious in 8 eyes. CONCLUSIONS: The use of laser therapy in the main maintenance period of anti-CMV treatment can effectively reduce the incidence of retinal detachment in patients with AIDS and CMVR, and the therapy is safe and reliable.

A ratiometric fluorescent probe based on quinoline for monitoring and imaging of Leucine aminopeptidase in liver tumor cells.

Leucine aminopeptidase (LAP) is known as an important potential biomarker for liver malignancy and it is urgent to develop an intuitive and effective method to monitor the activity of LAP in liver cancer. Although, numerous LAP fluorescent probes had been developed, it is still a challenge to detect LAP activity in liver cancer. Herein, combained with the DFT, we reported a novel galactose-appended hepatoma-specific ratiometric fluorescent probe (Gal-QL-Leu) based on quinoline group for imaging and tracing LAP in liver tumor cells. Probe Gal-QL-Leu demonstrated a obvious ratiometric characteristics, better selectivity, good biocompatibility and high sensitivity. Moreover, the selective imaging of LAP in HepG2, HCT116, A549 and HeLa cells had been achieved with probe Gal-QL-Leu, demonstrating good application prospect in the detection of LAP activity in liver tumor cells.

Design, synthesis and evaluation of a novel fluorescent probe to accurately detect H2S in hepatocytes and natural waters.

Design and synthesis of fluorescent probe with fast response, excellent water solubility and good hepatocyte-targeting capacity to detect hydrogen sulfide (H2S) in hepatocytes and water samples is of great significance. Here, a novel fluorescent probe QL-Gal-N3 for detection of H2S was designed and synthesized based on H2S-mediated azide reduction strategy. This sensor demonstrated low toxicity, fast response (within 1 min), high selectivity and low detection limit (as low as 126 nM in water) for the detection of H2S. HeLa, A549 and HepG-2 cells were chosen to investigate the hepatocyte-targeting ability of QL-Gal-N3 respectively. The results indicated that the specific recognition of ASGPR over-expressed in hepatocytes by galactose group was an important reason for the good targeting ability of probe QL-Gal-N3. Furthermore, due to the introduction of glycosyl moiety, the water solubility of fluorescent probe was enhanced obviously. It was successfully applied for the detection of H2S in environmental water samples including river water, tap water, lake water and waste water.

Integrated lipid production, CO2 fixation, and removal of SO2 and NO from simulated flue gas by oleaginous Chlorella pyrenoidosa.

CO2, SO2, and NO are the main components of flue gas and can cause serious environmental issues. Utilization of these compounds in oleaginous microalgae cultivation not only could reduce air pollution but could also produce feedstock for biodiesel production. However, the continuous input of SO2 and NO inhibits microalgal growth. In this study, the toxicity of simulated flue gas (15% CO2, 0.03% SO2, and 0.03% NO, balanced with N2) was reduced through automatic pH feedback control. Integrated lipid production and CO2 fixation with the removal of SO2 and NO was achieved. Using this technique, a lipid content of 38.0% DW was achieved in Chlorella pyrenoidosa XQ-20044. The lipid composition and fatty acid profile indicated that lipid production by C. pyrenoidosa XQ-20044 cultured with flue gas is suitable as a biodiesel feedstock; 81.2% of the total lipids were neutral lipids and 99.5% of the total fatty acids were C16 and C18. The ratio of saturated fatty acids to monounsaturated fatty acids in the microalgal lipid content was 74.5%. In addition, CO2, SO2, and NO from the simulated flue gas were fixed and converted to biomass and lipids with a removal efficiency of 95.9%, 100%, and 84.2%, respectively. Furthermore, the utilization efficiencies of CO2, SO2, and NO were equal to or very close to their removal efficiencies. These results provide a novel strategy for combining biodiesel production with biofixation of flue gas.

Small molecule PROTACs in targeted therapy: An emerging strategy to induce protein degradation.

Inhibitors and nucleic acid based techniques were two main approaches to interfere with protein signaling and respective cascade in the past. Until recently, a new class of small molecules named proteolysis-targeting chimeras (PROTACs) have emerged. Each contains a target warhead, a linker and an E3 ligand. These bifunctional molecules recruit E3 ligases and target specific proteins for degradation via the ubiquitin (Ub) proteasome system (UPS). The degradation provides several advantages over inhibition in potency, selectivity and drug resistance. Thus, a variety of small molecule PROTACs have been discovered so far. In this review, we summarize the biological mechanism, advantages and recent progress of PROTACs, trying to offer an outlook in development of drugs targeting degradation in future.

Design and synthesis of a new fluorescent probe for cascade detection of Zn2+ and H2 PO4 - in water and targeted imaging of living cells.

Design and synthesis of new fluorescence probes with good water-solubility is of great importance to better understanding the significant role of ions which are related to biology and the environment. As important ions, zinc ion (Zn2+ ) and dihydrogen phosphate ion (H2 PO4 - ) display essential roles in living systems, and quantitative detection of these ions in water is still a challenge. In order to consider the significant role of the galactose moiety in the design of a water-soluble fluorescence sensor, herein, we have developed a novel probe, Gal-AQTF, for the cascade detection of Zn2+ and H2 PO4 - with excellent selectivity in water. Through the introduction of the galactose moiety onto the sensor AQTF, which has been reported earlier by us, the water-solubility, cell compatibility and targeting ability were enhanced. Gal-AQTF has been successfully applied in the imaging of the living cells of HepG2 and A549, and illustrated good selectivity for the HepG2 cells which overly express the asialoglycoprotein (ASGP) receptor.

CDK8 as a therapeutic target for cancers and recent developments in discovery of CDK8 inhibitors.

Cyclin-dependent kinases 8 (CDK8) regulates transcriptional process via associating with the mediator complex or phosphorylating transcription factors (TF). Overexpression of CDK8 has been observed in various cancers. It mediates aberrant activation of Wnt/ß-catenin signaling pathway, which is initially recognized and best studied in colorectal cancer (CRC). CDK8 acts as an oncogene and represents a potential target for developing novel CDK8 inhibitors in cancer therapeutics. However, other study has revealed its contrary role. The function of CDK8 is context dependent. Even so, a variety of potent and selective CDK8 inhibitors have been discovered after crystal structures were resolved in two states (active or inactive). In this review, we summarize co-crystal structures, biological mechanisms, dysregulation in cancers and recent progress in the field of CDK8 inhibitors, trying to offer an outlook of CDK8 inhibitors in cancer therapy in future.

Synthesis and anti-tumor activity of glycosyl oxadiazoles derivatives.

A new series of glycosyl oxadiazoles compounds were synthesized and characterized through (1)H NMR, (13)C NMR, IR and HRMS. The anti-tumor activities for MDA-MB-231 of all these new compounds were screened in vitro by MTT assay. Due to the modification of gastrodin analogues, the anti-tumor activities of these 1,3,4-oxadiazoles derivatives were greatly improved. Six compounds (6 c, 6 d, 6 i, 6 j, 6 k and 6 l) displayed relatively higher MDA-MB-231 potency with IC50 values (0.89, 0.26, 1.35, 3.60, 0.95 and 1.08 µM) compared with the reference medicine Rosiglitazone (5.23 µM).

Subfoveal choroidal thickness: the Beijing Eye Study.

PURPOSE: To study subfoveal choroidal thickness (SFCT) in adult Chinese subjects and its correlation with ocular biometric parameters, refractive error, and age. DESIGN: Population-based longitudinal study. PARTICIPANTS: The population-based Beijing Eye Study 2011 included 3468 individuals with a mean age of 64.6±9.8 years (range, 50-93 years). METHODS: A detailed ophthalmic examination was performed, including spectral-domain optical coherence tomography (SD-OCT) with enhanced depth imaging for measurement of SFCT. MAIN OUTCOME MEASURES: Subfoveal choroidal thickness. RESULTS: The SFCT measurements were available for 3233 subjects (93.2%). Mean SFCT was 253.8±107.4 µm (range, 8-854 µm). In multivariate analysis, SFCT increased with younger age (P<0.001; correlation coefficient r=4.12; beta coefficient=0.37), shorter axial length (P<0.001; r=44.7; beta coefficient=0.46), male gender (P<0.001; r=28.5; beta coefficient=-0.13), deeper anterior chamber depth (P<0.001; r=39.3; beta coefficient=0.13), thicker lens (P<0.001; r=26.8; beta coefficient=0.08), flatter cornea (P<0.001; r=46.0; beta coefficient=0.11), and better best-corrected visual acuity (BCVA) (logarithm of minimal angle of resolution; P=0.001; r=48.4; beta coefficient=0.06). In multivariate analysis, SFCT was not significantly associated with blood pressure, ocular perfusion pressure, intraocular pressure, cigarette smoking, alcohol consumption, serum concentrations of lipids and glucose, diabetes mellitus, and arterial hypertension. In the myopic refractive error range of more than -1 diopter (D), SFCT decreased by 15 µm (95% confidence interval [CI], 11.9-18.5) for every increase in myopic refractive error of 1 D, or by 32 µm (95% CI, 37.1-26.0) for every increase in axial length of 1 mm. For each year increase in age, the SFCT decreased by 4.1 µm (95% CI, 4.6-3.7) (multivariate analysis). CONCLUSIONS: Subfoveal choroidal thickness with a mean of 254±107 µm in elderly subjects with a mean age of 65 years decreased with age (4 µm per year of age) and myopia (15 µm per diopter [D] of myopia). It was also associated with male gender and the ocular biometric parameters of a deeper anterior chamber and thicker lens. The association between SFCT and BCVA indicates a functional aspect of SFCT. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.