PIAS1-mediated SUMOylation of influenza A virus PB2 restricts viral replication and virulence.

Host defense systems employ posttranslational modifications to protect against invading pathogens. Here, we found that protein inhibitor of activated STAT 1 (PIAS1) interacts with the nucleoprotein (NP), polymerase basic protein 1 (PB1), and polymerase basic protein 2 (PB2) of influenza A virus (IAV). Lentiviral-mediated stable overexpression of PIAS1 dramatically suppressed the replication of IAV, whereas siRNA knockdown or CRISPR/Cas9 knockout of PIAS1 expression significantly increased virus growth. The expression of PIAS1 was significantly induced upon IAV infection in both cell culture and mice, and PIAS1 was involved in the overall increase in cellular SUMOylation induced by IAV infection. We found that PIAS1 inhibited the activity of the viral RNP complex, whereas the C351S or W372A mutant of PIAS1, which lacks the SUMO E3 ligase activity, lost the ability to suppress the activity of the viral RNP complex. Notably, the SUMO E3 ligase activity of PIAS1 catalyzed robust SUMOylation of PB2, but had no role in PB1 SUMOylation and a minimal role in NP SUMOylation. Moreover, PIAS1-mediated SUMOylation remarkably reduced the stability of IAV PB2. When tested in vivo, we found that the downregulation of Pias1 expression in mice enhanced the growth and virulence of IAV. Together, our findings define PIAS1 as a restriction factor for the replication and pathogenesis of IAV.

Mechanistic Study on the Effect of Renal Impairment on the Pharmacokinetics of Vildagliptin and its Carboxylic Acid Metabolite.

PURPOSE: To clarify the mechanism of renal impairment leading to different degrees of increased plasma exposure to dipeptidyl peptidase 4 inhibitor vildagliptin and its major metabolite, M20.7. METHODS: The 5/6 nephrectomized (5/6 Nx) rat model, to simulate chronic renal failure (CRF) patients, combined with kidney slices and transporter studies in vitro were used to assess this pharmacokinetic differences. RESULTS: After intragastric administration to 5/6 Nx rats, vildagliptin showed increased plasma levels by 45.8%, and M20.7 by 7.51 times, which was similar to patients with severe renal impairment. The recovery rate of M20.7 in urine and feces increased by less than 20%, showing limited effect of renal impairment on vildagliptin metabolism. In vitro studies found M20.7 to be the substrate for organic anion transporter 3 (OAT3). However, the active uptake of M20.7 in renal slices showed no difference between the 5/6 Nx and normal rats. In OAT3 overexpressed cells, the protein-bound uremic toxins, 3-carboxy-4-methyl-5propyl-2-furanpropionate (CMPF), hippuric acid (HA) and indoxyl sulfate (IS), which accumulate in CRF patients, inhibited M20.7 uptake with IC50 values of 5.75, 29.0 and 69.5 µM respectively, far lower than plasma concentrations in CRF patients, and showed a mixed inhibition type. CONCLUSIONS: The large increase in plasma exposure of M20.7 could be attributed to the accumulation of uremic toxins in CRF patients, which inhibited OAT3 activity and blocked renal excretion of M20.7, while vildagliptin, with high permeability, showed a slight increase in plasma exposure due to reduced glomerular filtration.

The G Protein-Coupled Receptor FFAR2 Promotes Internalization during Influenza A Virus Entry.

Influenza A virus (IAV) coopts numerous host factors to complete its replication cycle. Here, we identify free fatty acid receptor 2 (FFAR2) as a cofactor for IAV entry into host cells. We found that downregulation of FFAR2 or Ffar2 expression significantly reduced the replication of IAV in A549 or RAW 264.7 cells. The treatment of A549 cells with small interfering RNA (siRNA) targeting FFAR2 or the FFAR2 pathway agonists 2-(4-chlorophenyl)-3-methyl-N-(thiazol-2-yl)butanamide (4-CMTB) and compound 58 (Cmp58) [(S)-2-(4-chlorophenyl)-3,3-dimethyl-N-(5-phenylthiazol-2-yl)butanamide] dramatically inhibited the nuclear accumulation of viral nucleoprotein (NP) at early time points postinfection, indicating that FFAR2 functions in the early stage of the IAV replication cycle. FFAR2 downregulation had no effect on the expression of sialic acid (SA) receptors on the cell membrane, the attachment of IAV to the SA receptors, or the activity of the viral ribonucleoprotein (vRNP) complex. Rather, the amount of internalized IAVs was significantly reduced in FFAR2-knocked-down or 4-CMTB- or Cmp58-treated A549 cells. Further studies showed that FFAR2 associated with ß-arrestin1 and that ß-arrestin1 interacted with the ß2-subunit of the AP-2 complex (AP2B1), the essential adaptor of the clathrin-mediated endocytosis pathway. Notably, siRNA knockdown of either ß-arrestin1 or AP2B1 dramatically impaired IAV replication, and AP2B1 knockdown or treatment with Barbadin, an inhibitor targeting the ß-arrestin1/AP2B1 complex, remarkably decreased the amount of internalized IAVs. Moreover, we found that FFAR2 interacted with three G protein-coupled receptor (GPCR) kinases (i.e., GRK2, GRK5, and GRK6) whose downregulation inhibited IAV replication. Together, our findings demonstrate that the FFAR2 signaling cascade is important for the efficient endocytosis of IAV into host cells.IMPORTANCE To complete its replication cycle, IAV hijacks the host endocytosis machinery to invade cells. However, the underlying mechanisms of how IAV is internalized into host cells remain poorly understood, emphasizing the need to elucidate the role of host factors in IAV entry into cells. In this study, we identified FFAR2 as an important host factor for the efficient replication of both low-pathogenic and highly pathogenic IAV. We revealed that FFAR2 facilitates the internalization of IAV into target cells during the early stage of infection. Upon further characterization of the role of FFAR2-associated proteins in virus replication, we found that the FFAR2-ß-arrestin1-AP2B1 signaling cascade is important for the efficient endocytosis of IAV. Our findings thus further our understanding of the biological details of IAV entry into host cells and establish FFAR2 as a potential target for antiviral drug development.

Hydrolytic Metabolism of Cyanopyrrolidine DPP-4 Inhibitors Mediated by Dipeptidyl Peptidases.

Nitrile group biotransformation is an unusual or minor metabolic pathway for most nitrile-containing drugs. However, for some cyanopyrrolidine dipeptidyl peptidase 4 (DPP-4) inhibitors (vildagliptin, anagliptin, and besigliptin, but not saxagliptin), the conversion of nitrile group into carboxylic acid is their major metabolic pathway in vivo. DPP-4 was reported to be partly involved in the metabolism. In our pilot study, it was also observed that saxagliptin, a DPP-4 specific inhibitor, decreased the plasma exposures of besigliptin carboxylic acid in rats by only 20%. Therefore, it is speculated that some other enzymes may participate in nitrile group hydrolysis. After incubating gliptins with the cytosol, microsomes, and mitochondria of liver and kidney, carboxylic acid metabolites could all be formed. In recombinant DPP family such as DPP-4, DPP-2, DPP-8, DPP-9, and fibroblast activation protein-α, more hydrolytic metabolites were found. Among them, DPP-2 had the highest hydrolytic capacity besides DPP-4, and the DPP-4 inhibitor saxagliptin and DPP-2 inhibitor AX8819 can both inhibit the hydrolysis of gliptins. Western blot results showed that DPP-2 and DPP-4 existed in the aforementioned subcellular organelles at varying amounts. In rats, AX8819 decreased the plasma exposures of besigliptin carboxylic acid by 40%. The amide intermediates of gliptins were detected in vivo and in vitro. When the amide derivatives of gliptins were incubated with DPP-4, they were completely hydrolyzed at a rate far more than that from the parent drug, including saxagliptin-amide. Therefore, it was proposed that gliptins, except saxagliptin, were initially hydrolyzed to their amides by DPPs, which was the rate-limiting step in generating the carboxylic end product.

Increased Plasma Exposures of Conjugated Metabolites of Morinidazole in Renal Failure Patients: A Critical Role of Uremic Toxins.

Morinidazole is a 5-nitroimidazole drug. Its sulfate conjugate M7 was a sensitive substrate of organic anion transporter 1 (OAT1) and OAT3, whereas N+-glucuronides M8-1 and M8-2 were only OAT3 substrates. In chronic renal failure (CRF) patients, plasma exposures of the three conjugates increased by 15-fold, which were also found in 5/6 nephrectomized (5/6 Nx) rats in this study. Although the transcriptions of Oat1 and Oat3 in 5/6 Nx rat kidneys decreased by 50%, no difference was observed on the three conjugate uptakes between control and 5/6 Nx rat kidney slices. Thus, the highly elevated endogenous uremic toxins in 5/6 Nx rats and humans, namely, 3-carboxy-4-methyl-5-propyl-2-furanpropionate (CMPF), hippuric acid (HA), and indoxyl sulfate (IS), were considered as influential factors. In rat kidney slices, the uptake of M7, M8-1, and M8-2 was dose dependently reduced by HA and IS, whose plasma concentrations were elevated 5 times in 5/6 Nx rats. In OAT3-overexpressed cells, the three conjugate uptakes were inhibited by CMPF, HA, and IS with IC50 values of 19.2, 87.4, and 222 µM (M7); 8.53, 39.4, and 161 µM (M8-1); and 6.75, 24.1, and 78.3 µM (M8-2), respectively. In OAT1-overexpressed cells, CMPF, HA, and IS showed weak inhibition on M7 uptake with IC50 values of 187, 162, and 200 µM, correspondingly. Results suggest that the reduced mRNA expression of renal transporters in CRF patients may not influence the activities of these transporters. However, accumulated uremic toxins may inhibit the transporters, particularly OAT3, leading to plasma exposure changes of relevant substrates.

Development and characterization of curcumin-loaded chitosan/egg yolk freshness-keeping edible films for chilled fresh pork packaging application.

In this study, a novel fresh-keeping edible film was prepared using egg yolk (EY) and chitosan (CS) with varying concentrations of curcumin (Cur) for food packaging. The addition of Cur notably enhanced tensile strength, elongation at break, and water resistance from 15.70 MPa to 24.24 MPa, 43.79 % to 63.69 %, and 1.599 g·mm·(m2·h·kPa)-1 to 1.541 g·mm·(m2·h·kPa)-1, respectively. Cur also impacted moisture content, swelling degree, and film color. SEM revealed a uniform distribution of Cur, creating a smooth and dense film surface. FT-IR analysis suggested that hydrogen bonding facilitated Cur integration into the film network. The films demonstrated excellent UV-blocking and antioxidant properties attributed to Cur's chromogenic and phenolic hydroxyl groups. Consequently, they effectively inhibited lipid oxidation and weight loss in meat, thereby prolonging the shelf-life of chilled pork by at least 2 d. In conclusion, this study provided a simple and cost-effective idea to incorporate actives with EY as a natural emulsifier, presenting an effective solution for developing active packaging materials to enhance the safety and quality of meat products.

Janus liposozyme for the modulation of redox and immune homeostasis in infected diabetic wounds.

Diabetic foot ulcers often become infected, leading to treatment complications and increased risk of loss of limb. Therapeutics to manage infection and simultaneously promote healing are needed. Here we report on the development of a Janus liposozyme that treats infections and promotes wound closure and re-epithelialization. The Janus liposozyme consists of liposome-like selenoenzymes for reactive oxygen species (ROS) scavenging to restore tissue redox and immune homeostasis. The liposozymes are used to encapsulate photosensitizers for photodynamic therapy of infections. We demonstrate application in methicillin-resistant Staphylococcus aureus-infected diabetic wounds showing high ROS levels for antibacterial function from the photosensitizer and nanozyme ROS scavenging from the liposozyme to restore redox and immune homeostasis. We demonstrate that the liposozyme can directly regulate macrophage polarization and induce a pro-regenerative response. By employing single-cell RNA sequencing, T cell-deficient Rag1-/- mice and skin-infiltrated immune cell analysis, we further reveal that IL-17-producing γδ T cells are critical for mediating M1/M2 macrophage transition. Manipulating the local immune homeostasis using the liposozyme is shown to be effective for skin wound repair and tissue regeneration in mice and mini pigs.

Foxo1 Drives the TGFß1-Dependent Dichotomy of Th17 Cell Fates.

T-helper 17 (Th17) cells play a dual role in immunological responses, serving as essential components in tissue homeostasis and host defense against microbial pathogens while also contributing to pro-inflammatory conditions and autoimmunity. While Transforming Growth Factor-beta 1 (TGFß1) is pivotal for the differentiation of non-pathogenic Th17 cells, the role of TGFß3 and Activin in steering Th17 cells toward a pathogenic phenotype has been acknowledged. However, the molecular mechanisms governing this dichotomy remain elusive. In this study, we demonstrate that the transcription factor Foxo1 is upregulated in a TGFß1 dose-dependent manner, serving as a critical regulator that specifically modulates the fate of pathogenic Th17 cells. Analyses in both uveitis patients and an Experimental Autoimmune Uveitis (EAU) mouse model reveal a strong correlation between disease severity and diminished Foxo1 expression levels. Ectopic expression of Foxo1 selectively attenuates IL-17A production under pathogenic Th17-inducing conditions. Moreover, enhanced Foxo1 expression, triggered by TGFß1 signaling, is implicated in fatty acid metabolism pathways that favor non-pathogenic Th17 differentiation. Our drug screening identifies several FDA-approved compounds can upregulate Foxo1. Collectively, our findings offer evidence that Foxo1 serves as a molecular switch to specifically control pathogenic versus non-pathogenic Th17 differentiation in a TGFß1-dependent manner. Suggest that targeting Foxo1 could be a promising therapeutic strategy for autoimmune diseases.

CYP2C and CYP2B Mediated Metabolic Activation of Retrorsine in Cyp3a Knockout Mice.

BACKGROUND: Retrorsine is one of the hepatotoxic pyrrolizidine alkaloids, which could be converted into a highly reactive metabolite, dehydroretrorsine, by CYP3A, and to a lesser extent by CYP2C and CYP2B. OBJECTIVE: We employed Cyp3a knockout (3AKO) mice to investigate whether the absence of CYP3A could attenuate dehydroretrorsine formation and the role of CYP2C and CYP2B in the formation. METHODS: Blood and liver samples were collected after intragastrical administration of 35 mg/kg retrorsine or saline for seven days in wild-type (WT) and 3AKO mice. Blood pyrrole-protein adducts were semi quantified by high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry. The formations of glutathionyl-6,7-dihydro-1-hydroxymethyl-5H-pyrrolizine (GSH-DHP) and the activities of CYP3A, CYP2B and CYP2C were evaluated in the liver microsomes of WT and 3AKO mice before and after treatment. The metabolic phenotype of retrorsine was determined in human liver microsomes. The gene and protein expression of retrorsine metabolism-related CYP450s in the liver was measured by quantitative real-time PCR method and western blotting method. The serum cytokine level was detected by the ELISA method to reveal the potential mechanism of Cyp3a, Cyp2b and Cyp2c downregulation. RESULTS: After an oral administration of 35 mg/kg retrorsine for seven days, the blood exposures of DHP adducts between WT and 3AKO mice were similar, consistent with the comparable formation of GSH-DHP in their liver microsomes. The chemical inhibitor experiment in liver microsomes indicated the predominant role of CYP3A and CYP2C in GSH-DHP formation in WT and 3AKO mice, respectively. Real-time qPCR analysis showed that the expressions of Cyp2b10 and Cyp2cs increased 2.3-161-fold in 3AKO mice, which was consistent with protein changes. The increased CYP2B activity in 3AKO mice supported the potential role of CYP2B in GSH-DHP formation. After a seven-day treatment of retrorsine, the yields of GSH-DHP were lower than the untreated ones in both alleles, accompanied by the decreased mRNA of Cyp3a, Cyp2b and Cyp2c. The increased serum IL6 might mediate the retrorsine-induced downregulation of Cyp450s. CONCLUSION: These data demonstrated the increased transcription of Cyp2c and Cyp2b caused by Cyp3a ablation, which played a vital role in the metabolic activation of retrorsine, and long-term exposure of retrorsine can reduce the CYP450 activities.

Generation and application of replication-competent Venus-expressing H5N1, H7N9, and H9N2 influenza A viruses.

The generation and application of replication-competent influenza A virus (IAV) expressing a reporter gene represent a valuable tool to elucidate the mechanism of viral pathogenesis and establish new countermeasures to combat the threat of influenza. Here, replication-competent IAVs with a neuraminidase (NA) segment harboring a fluorescent reporter protein, Venus, were generated in the background of H5N1, H7N9, and H9N2 influenza viruses, the three subtypes of viruses with imminent pandemic potential. All three reporter viruses maintained virion morphology, replicated with similar or slightly reduced titers relative to their parental viruses, and stably expressed the fluorescent signal for at least two passages in embryonated chicken eggs. As a proof of concept, we demonstrated that these reporter viruses, used in combination with a high-content imaging system, can serve as a convenient and rapid tool for the screening of antivirals and host factors involved in the virus life cycle. Moreover, the reporter viruses demonstrated similar growth properties and tissue tropism as their parental viruses in mice, among which the H7N9 NA-Venus virus could potentially be used in ex vivo studies to better understand H7N9 pathogenesis or to develop novel therapeutics.