Dipeptidyl peptidase 9 sets a threshold for CARD8 inflammasome formation by sequestering its active C-terminal fragment.

CARD8 detects intracellular danger signals and forms a caspase-1 activating inflammasome. Like the related inflammasome sensor NLRP1, CARD8 autoprocesses into noncovalently associated N-terminal (NT) and C-terminal (CT) fragments and binds the cellular dipeptidyl peptidases DPP8 and 9 (DPP8/9). Certain danger-associated signals, including the DPP8/9 inhibitor Val-boroPro (VbP) and HIV protease, induce proteasome-mediated NT degradation and thereby liberate the inflammasome-forming CT. Here, we report cryoelectron microscopy (cryo-EM) structures of CARD8 bound to DPP9, revealing a repressive ternary complex consisting of DPP9, full-length CARD8, and CARD8-CT. Unlike NLRP1-CT, CARD8-CT does not interact with the DPP8/9 active site and is not directly displaced by VbP. However, larger DPP8/9 active-site probes can directly weaken this complex in vitro, and VbP itself nevertheless appears to disrupt this complex, perhaps indirectly, in cells. Thus, DPP8/9 inhibitors can activate the CARD8 inflammasome by promoting CARD8 NT degradation and by weakening ternary complex stability.

Protease-mediated processing of Argonaute proteins controls small RNA association.

Small RNA pathways defend the germlines of animals against selfish genetic elements, yet pathway activities need to be contained to prevent silencing of self genes. Here, we reveal a proteolytic mechanism that controls endogenous small interfering (22G) RNA activity in the Caenorhabditis elegans germline to protect genome integrity and maintain fertility. We find that DPF-3, a P-granule-localized N-terminal dipeptidase orthologous to mammalian dipeptidyl peptidase (DPP) 8/9, processes the unusually proline-rich N termini of WAGO-1 and WAGO-3 Argonaute (Ago) proteins. Without DPF-3 activity, these WAGO proteins lose their proper complement of 22G RNAs. Desilencing of repeat-containing and transposon-derived transcripts, DNA damage, and acute sterility ensue. These phenotypes are recapitulated when WAGO-1 and WAGO-3 are rendered resistant to DPF-3-mediated processing, identifying them as critical substrates of DPF-3. We conclude that N-terminal processing of Ago proteins regulates their activity and promotes silencing of selfish genetic elements by ensuring Ago association with appropriate small RNAs.

Microbial gatekeepers: unraveling the role of the gut microbiota enzyme DPP4 in diabetes management.

Wang et al. identified dipeptidyl peptidase 4 (DPP4) as a gut microbe-derived enzyme that impacts on host glucose metabolism. They further introduced a novel therapeutic, daurisoline-d4 (Dau-d4), a selective microbial DPP4 (mDPP4) inhibitor that shows promise in improving glucose tolerance, highlighting the potential of therapies that target both host enzymes and gut microbial enzymes.

Muscle-derived Dpp regulates feeding initiation via endocrine modulation of brain dopamine biosynthesis.

In animals, the brain regulates feeding behavior in response to local energy demands of peripheral tissues, which secrete orexigenic and anorexigenic hormones. Although skeletal muscle is a key peripheral tissue, it remains unknown whether muscle-secreted hormones regulate feeding. In Drosophila, we found that decapentaplegic (dpp), the homolog of human bone morphogenetic proteins BMP2 and BMP4, is a muscle-secreted factor (a myokine) that is induced by nutrient sensing and that circulates and signals to the brain. Muscle-restricted dpp RNAi promotes foraging and feeding initiation, whereas dpp overexpression reduces it. This regulation of feeding by muscle-derived Dpp stems from modulation of brain tyrosine hydroxylase (TH) expression and dopamine biosynthesis. Consistently, Dpp receptor signaling in dopaminergic neurons regulates TH expression and feeding initiation via the downstream transcriptional repressor Schnurri. Moreover, pharmacologic modulation of TH activity rescues the changes in feeding initiation due to modulation of dpp expression in muscle. These findings indicate that muscle-to-brain endocrine signaling mediated by the myokine Dpp regulates feeding behavior.

Pharmacological expansion of type 2 alveolar epithelial cells promotes regenerative lower airway repair.

Type 2 alveolar epithelial cells (AEC2s) are stem cells in the adult lung that contribute to lower airway repair. Agents that promote the selective expansion of these cells might stimulate regeneration of the compromised alveolar epithelium, an etiology-defining event in several pulmonary diseases. From a high-content imaging screen of the drug repurposing library ReFRAME, we identified that dipeptidyl peptidase 4 (DPP4) inhibitors, widely used type 2 diabetes medications, selectively expand AEC2s and are broadly efficacious in several mouse models of lung damage. Mechanism of action studies revealed that the protease DPP4, in addition to processing incretin hormones, degrades IGF-1 and IL-6, essential regulators of AEC2 expansion whose levels are increased in the luminal compartment of the lung in response to drug treatment. To selectively target DPP4 in the lung with sufficient drug exposure, we developed NZ-97, a locally delivered, lung persistent DPP4 inhibitor that broadly promotes efficacy in mouse lung damage models with minimal peripheral exposure and good tolerability. This work reveals DPP4 as a central regulator of AEC2 expansion and affords a promising therapeutic approach to broadly stimulate regenerative repair in pulmonary disease.

Beta-endoproteolysis of the cellular prion protein by dipeptidyl peptidase-4 and fibroblast activation protein.

The cellular prion protein (PrPC) converts to alternatively folded pathogenic conformations (PrPSc) in prion infections and binds neurotoxic oligomers formed by amyloid-ß α-synuclein, and tau. ß-Endoproteolysis, which splits PrPC into N- and C-terminal fragments (N2 and C2, respectively), is of interest because a protease-resistant, C2-sized fragment (C2Sc) accumulates in the brain during prion infections, seemingly comprising the majority of PrPSc at disease endpoint in mice. However, candidates for the underlying proteolytic mechanism(s) remain unconfirmed in vivo. Here, a cell-based screen of protease inhibitors unexpectedly linked type II membrane proteins of the S9B serine peptidase subfamily to PrPC ß-cleavage. Overexpression experiments in cells and assays with recombinant proteins confirmed that fibroblast activation protein (FAP) and its paralog, dipeptidyl peptidase-4 (DPP4), cleave directly at multiple sites within PrPC's N-terminal domain. For wild-type mouse and human PrPC substrates expressed in cells, the rank orders of activity were human FAP ~ mouse FAP > mouse DPP4 > human DPP4 and human FAP > mouse FAP > mouse DPP4 >> human DPP4, respectively. C2 levels relative to total PrPC were reduced in several tissues from FAP-null mice, and, while knockout of DPP4 lacked an analogous effect, the combined DPP4/FAP inhibitor linagliptin, but not the FAP-specific inhibitor SP-13786, reduced C2Sc and total PrPSc levels in two murine cell-based models of prion infections. Thus, the net activity of the S9B peptidases FAP and DPP4 and their cognate inhibitors/modulators affect the physiology and pathogenic potential of PrPC.

GSL-DTI: Graph structure learning network for Drug-Target interaction prediction.

MOTIVATION: Drug-target interaction prediction is an important area of research to predict whether there is an interaction between a drug molecule and its target protein. It plays a critical role in drug discovery and development by facilitating the identification of potential drug candidates and expediting the overall process. Given the time-consuming, expensive, and high-risk nature of traditional drug discovery methods, the prediction of drug-target interactions has become an indispensable tool. Using machine learning and deep learning to tackle this class of problems has become a mainstream approach, and graph-based models have recently received much attention in this field. However, many current graph-based Drug-Target Interaction (DTI) prediction methods rely on manually defined rules to construct the Drug-Protein Pair (DPP) network during the DPP representation learning process. However, these methods fail to capture the true underlying relationships between drug molecules and target proteins. RESULTS: We propose GSL-DTI, an automatic graph structure learning model used for predicting drug-target interactions (DTIs). Initially, we integrate large-scale heterogeneous networks using a graph convolution network based on meta-paths, effectively learning the representations of drugs and target proteins. Subsequently, we construct drug-protein pairs based on these representations. In contrast to previous studies that construct DPP networks based on manual rules, our method introduces an automatic graph structure learning approach. This approach utilizes a filter gate on the affinity scores of DPPs and relies on the classification loss of downstream tasks to guide the learning of the underlying DPP network structure. Based on the learned DPP network, we transform the prediction of drug-target interactions into a node classification problem. The comprehensive experiments conducted on three public datasets have shown the superiority of GSL-DTI in the tasks of DTI prediction. Additionally, GSL-DTI provides a fresh perspective for advancing research in graph structure learning for DTI prediction.

Rab11 maintains the undifferentiated state of adult midgut precursors via DPP pathway.

Asymmetric stem cell divisions play instrumental roles in the maintenance, growth and differentiation of organs. Failure of asymmetric stem cell divisions may result in an array of developmental disorders, including cancer. It is well established that the gene, inscuteable, acts as the upstream component of asymmetric cell divisions. In Drosophila larval midgut, a founder adult midgut precursor (AMP) experiences an asymmetric division to instruct its first daughter to become a peripheral cell that serves as a niche where the AMP and its future daughters can remain undifferentiated. The present study demonstrates that inscuteable expressing stem cells require Rab11, a conserved small Ras-like GTPase, for proper proliferation and differentiation. As insc-GAL4 mediated Rab11RNAi in Drosophila larval and adult midguts show the disruption of the niche microenvironment of adult midgut precursors as well as elevated DPP signalling at the larval stage, which is associated with aberrant over-proliferation and early differentiation of larval AMPs and adult intestinal stem cells. The observed connections between Rab11, larval AMP proliferation, niche establishment, and DPP signalling highlight the potential for Rab11 to serve as a key regulatory factor in maintaining tissue homeostasis and balanced cellular growth.

SOX9 promotes hypoxic pulmonary hypertension through stabilization of DPP4 in pulmonary artery smooth muscle cells.

Pulmonary hypertension (PH) is a progressive cardiopulmonary disorder characterized by pulmonary vascular remodeling (PVR), primarily due to the excessive proliferation of pulmonary artery smooth muscle cells (PASMCs). This study aimed to investigate the role and molecular mechanism of SOX9 in hypoxic PH in rats. The findings revealed that SOX9 was upregulated in the pulmonary arteries and PASMCs of hypoxia-exposed rats. SOX9 knockdown inhibited hypoxia-induced proliferation and migration of PASMCs, reduced PVR, and subsequently alleviated hypoxia-induced PH in rats, suggesting that SOX9 plays a critical role in PH. Further investigation demonstrated that SOX9 interacted with DPP4, preventing its ubiquitin degradation in hypoxia-exposed PASMCs. DPP4 knockdown inhibited hypoxia-induced PASMC proliferation and migration, and administration of the DPP4 inhibitor sitagliptin (5 mg/kg) significantly reduced PVR and alleviated hypoxia-induced PH in rats, indicating that SOX9 contributes to PH by stabilizing DPP4. The results also showed that hypoxia induced YAP1 expression and dephosphorylation, leading to YAP1 nuclear localization. YAP1 knockdown promoted the degradation of HIF-1α in hypoxia-exposed PASMCs and inhibited hypoxia-induced proliferation and migration of PASMCs. Additionally, HIF-1α, as a transcription factor, promoted SOX9 expression by binding to the SOX9 promoter in hypoxia-exposed PASMCs. In conclusion, hypoxia promotes the proliferation and migration of PASMCs through the regulation of the YAP1/HIF-1α/SOX9/DPP4 signaling pathway, leading to PH in rats. These findings suggest that SOX9 may serve as a potential prognostic marker and therapeutic target for PH.

Is Drosophila Dpp/BMP morphogen spreading required for wing patterning and growth?

Secreted signaling molecules act as morphogens to control patterning and growth in many developing tissues. Since locally produced morphogens spread to form a concentration gradient in the surrounding tissue, spreading is generally thought to be the key step in the non-autonomous actions. Here, we review recent advances in tool development to investigate morphogen function using the role of decapentaplegic (Dpp)/bone morphogenetic protein (BMP)-type ligand in the Drosophila wing disc as an example. By applying protein binder tools to distinguish between the roles of Dpp spreading and local Dpp signaling, we found that Dpp signaling in the source cells is important for wing patterning and growth but Dpp spreading from this source cells is not as strictly required as previously thought. Given recent studies showing unexpected requirements of long-range action of different morphogens, manipulating endogenous morphogen gradients by synthetic protein binder tools could shed more light on how morphogens act in developing tissues.

Effectiveness and safety of empagliflozin: final results from the EMPRISE study.

AIMS/HYPOTHESIS: Limited evidence exists on the comparative safety and effectiveness of empagliflozin against alternative glucose-lowering medications in individuals with type 2 diabetes with the broad spectrum of cardiovascular risk. The EMPagliflozin compaRative effectIveness and SafEty (EMPRISE) cohort study was designed to monitor the safety and effectiveness of empagliflozin periodically for a period of 5 years with data collection from electronic healthcare databases. METHODS: We identified individuals ≥18 years old with type 2 diabetes who initiated empagliflozin or dipeptidyl peptidase-4 inhibitors (DPP-4i) from 2014 to 2019 using US Medicare and commercial claims databases. After 1:1 propensity score matching using 143 baseline characteristics, we identified four a priori-defined effectiveness outcomes: (1) myocardial infarction (MI) or stroke; (2) hospitalisation for heart failure (HHF); (3) major adverse cardiovascular events (MACE); and (4) cardiovascular mortality or HHF. Safety outcomes included lower-limb amputations, non-vertebral fractures, diabetic ketoacidosis (DKA), acute kidney injury (AKI), severe hypoglycaemia, retinopathy progression, and short-term kidney and bladder cancers. We estimated HRs and rate differences (RDs) per 1000 person-years, overall and stratified by age, sex, baseline atherosclerotic cardiovascular disease (ASCVD) and heart failure. RESULTS: We identified 115,116 matched pairs. Compared with DPP-4i, empagliflozin was associated with lower risks of MI/stroke (HR 0.88 [95% CI 0.81, 0.96]; RD -2.08 [95% CI (-3.26, -0.90]), HHF (HR 0.50 [0.44, 0.56]; RD -5.35 [-6.22, -4.49]), MACE (HR 0.73 [0.62, 0.86]; RD -6.37 [-8.98, -3.77]) and cardiovascular mortality/HHF (HR 0.57 [0.47, 0.69]; RD -10.36 [-12.63, -8.12]). Absolute benefits were larger in older individuals and in those with ASCVD/heart failure. Empagliflozin was associated with an increased risk of DKA (HR 1.78 [1.44, 2.19]; RD 1.59 [1.08, 2.09]); decreased risks of AKI (HR 0.62 [0.54, 0.72]; RD -2.39 [-3.08, -1.71]), hypoglycaemia (HR 0.75 [0.67, 0.84]; RD -2.46 [-3.32, -1.60]) and retinopathy progression (HR 0.78 [0.63, 0.96)]; RD -9.49 [-16.97, -2.10]); and similar risks of other safety events. CONCLUSIONS/INTERPRETATION: Empagliflozin relative to DPP-4i was associated with risk reductions of MI or stroke, HHF, MACE and the composite of cardiovascular mortality or HHF. Absolute risk reductions were larger in older individuals and in those who had history of ASCVD or heart failure. Regarding the safety outcomes, empagliflozin was associated with an increased risk of DKA and lower risks of AKI, hypoglycaemia and progression to proliferative retinopathy, with no difference in the short-term risks of lower-extremity amputation, non-vertebral fractures, kidney and renal pelvis cancer, and bladder cancer.

Functional roles of CD26/DPP4 in lipopolysaccharide-induced lung injury.

Acute respiratory distress syndrome (ARDS) is characterized by dysregulated inflammation and increased permeability of lung microvascular cells. CD26/dipeptidyl peptidase-4 (DPP4) is a type II membrane protein that is expressed in several cell types and mediates multiple pleiotropic effects. We previously reported that DPP4 inhibition by sitagliptin attenuates lipopolysaccharide (LPS)-induced lung injury in mice. The current study characterized the functional role of CD26/DPP4 expression in LPS-induced lung injury in mice, isolated alveolar macrophages, and cultured lung endothelial cells. In LPS-induced lung injury, inflammatory responses [bronchoalveolar lavage fluid (BALF) neutrophil numbers and several proinflammatory cytokine levels] were attenuated in Dpp4 knockout (Dpp4 KO) mice. However, multiple assays of alveolar capillary permeability were similar between the Dpp4 KO and wild-type mice. TNF-α and IL-6 production was suppressed in alveolar macrophages isolated from Dpp4 KO mice. In contrast, in cultured mouse lung microvascular endothelial cells (MLMVECs), reduction in CD26/DPP4 expression by siRNA resulted in greater ICAM-1 and IL-6 expression after LPS stimulation. Moreover, the LPS-induced vascular monolayer permeability in vitro was higher in MLMVECs treated with Dpp4 siRNA, suggesting that CD26/DPP4 plays a protective role in endothelial barrier function. In summary, this study demonstrated that genetic deficiency of Dpp4 attenuates inflammatory responses but not permeability in LPS-induced lung injury in mice, potentially through differential functional roles of CD26/DPP4 expression in resident cellular components of the lung. CD26/DPP4 may be a potential therapeutic target for ARDS and warrants further exploration to precisely identify the multiple functional effects of CD26/DPP4 in ARDS pathophysiology.NEW & NOTEWORTHY We aimed to clarify the functional roles of CD26/DPP4 in ARDS pathophysiology using Dpp4-deficient mice and siRNA reduction techniques in cultured lung cells. Our results suggest that CD26/DPP4 expression plays a proinflammatory role in alveolar macrophages while also playing a protective role in the endothelial barrier. Dpp4 genetic deficiency attenuates inflammatory responses but not permeability in LPS-induced lung injury in mice, potentially through differential roles of CD26/DPP4 expression in the resident cellular components of the lung.

Dipeptidylpeptidase-4-targeted activatable fluorescent probes visualize senescent cells.

Senescent cells promote cancer development and progression through chronic inflammation caused by a senescence-associated secretory phenotype (SASP). Although various senotherapeutic strategies targeting senescent cells have been developed for the prevention and treatment of cancers, technology for the in vivo detection and evaluation of senescent cell accumulation has not yet been established. Here, we identified activatable fluorescent probes targeting dipeptidylpeptidase-4 (DPP4) as an effective probe for detecting senescent cells through an enzymatic activity-based screening of fluorescent probes. We also determined that these probes were highly, selectively, and rapidly activated in senescent cells during live cell imaging. Furthermore, we successfully visualized senescent cells in the organs of mice using DPP4-targeted probes. These results are expected to lead to the development of a diagnostic technology for noninvasively detecting senescent cells in vivo and could play a role in the application of DPP4 prodrugs for senotherapy.

Association of procurement technique with organ yield and cost following donation after circulatory death.

Donation after circulatory death (DCD) could account for the largest expansion of the donor allograft pool in the contemporary era. However, the organ yield and associated costs of normothermic regional perfusion (NRP) compared to super-rapid recovery (SRR) with ex-situ normothermic machine perfusion, remain unreported. The Organ Procurement and Transplantation Network (December 2019 to June 2023) was analyzed to determine the number of organs recovered per donor. A cost analysis was performed based on our institution's experience since 2022. Of 43 502 donors, 30 646 (70%) were donors after brain death (DBD), 12 536 (29%) DCD-SRR and 320 (0.7%) DCD-NRP. The mean number of organs recovered was 3.70 for DBD, 3.71 for DCD-NRP (P < .001), and 2.45 for DCD-SRR (P < .001). Following risk adjustment, DCD-NRP (adjusted odds ratio 1.34, confidence interval 1.04-1.75) and DCD-SRR (adjusted odds ratio 2.11, confidence interval 2.01-2.21; reference: DBD) remained associated with greater odds of allograft nonuse. Including incomplete and completed procurement runs, the total average cost of DCD-NRP was $9463.22 per donor. By conservative estimates, we found that approximately 31 donor allografts could be procured using DCD-NRP for the cost equivalent of 1 allograft procured via DCD-SRR with ex-situ normothermic machine perfusion. In conclusion, DCD-SRR procurements were associated with the lowest organ yield compared to other procurement methods. To facilitate broader adoption of DCD procurement, a comprehensive understanding of the trade-offs inherent in each technique is imperative.

Deltex modulates Dpp morphogen gradient formation and affects Dpp signaling in Drosophila.

Deltex (Dx) is a context-dependent regulator of Notch signaling that can act in a non-canonical fashion by facilitating the endocytosis of the Notch receptor. In an RNAi-based modifier screen of kinases and phosphatases, we identified Thickveins (Tkv), the receptor of Decapentaplegic (Dpp), as one of the interactors of Dx. Dpp, a Drosophila homolog of TGF-ß and bone morphogenetic proteins, acts as a morphogen to specify cell fate along the anterior-posterior axis of the wing. Tight regulation of Dpp signaling is thus indispensable for its proper functioning. Here, we present Dx as a novel modulator of Dpp signaling. We show evidence for the very first time that dx genetically interacts with dpp and its pathway components. Immunocytochemical analysis revealed that Dx colocalizes with Dpp and its receptor Tkv in Drosophila third-instar larval tissues. Furthermore, Dx was also seen to modulate the expression of dpp and its target genes, and we attribute this modulation to the involvement of Dx in the endocytosis and trafficking of Dpp. This study thus presents a whole new avenue of Dpp signaling regulation via the cytoplasmic protein Dx. This article has an associated First Person interview with the first author of the paper.

Immunomodulatory activity of dipeptidyl peptidase-4 inhibitors in immune-related diseases.

Dipeptidyl peptidase-4 (DPP-4), also known as CD26, is a 110-kDa cell surface glycoprotein with enzymatic and signal transducing activity. DPP-4/CD26 is expressed by various cells, including CD4+ and CD8+ T cells, B cells, dendritic cells, macrophages, and NK cells. DPP-4 inhibitors (DPP-4i) were introduced to clinics in 2006 as new oral antihyperglycemic drugs approved for type 2 diabetes mellitus treatment. In addition to glucose-lowering effects, emerging data, from clinical studies and their animal models, suggest that DPP-4i could display anti-inflammatory and immunomodulatory effects as well, but the molecular and immunological mechanisms of these actions are insufficiently investigated. This review focuses on the modulatory activity of DPP-4i in the immune system and the possible application of DPP-4i in other immune-related diseases in patients with or without diabetes.

Dipeptidyl peptidase 4: A predictor of ferroptosis in ulcerative colitis.

BACKGROUND: With its rapidly increasing incidence and prevalence, ulcerative colitis (UC) has become a major global health challenge. Recent evidence suggests that ferroptosis plays a significant role in the development of UC. However, the relationship between ferroptosis and the progression of UC needs to be extensively studied. METHODS: The differentially expressed genes in UC patients were screened from the GEO database. The ferroptosis-related genes were obtained from FErrDB and GeneCards. The UC subtypes were identified with the R package "CancerSubtype" and evaluated with consensus clustering (CC) to identify gene expression patterns in patients with UC. The key genes were detected with qRT-PCR, Western blot, and immunohistochemistry in vitro and in vivo models. Ferroptosis was identified with western blotting on ferrotic-associated proteins and staining on Fe2+ with commercial FerroOrange kits. RESULTS: Dipeptidyl peptidase 4 (DPP4), also known as CD26, is a potential biomarker for ferroptosis in UC patients. Transcriptome sequencing data showed a positive correlation between decreased DPP4 expression and proinflammatory cytokines such as TNF-α, IL-6, and IL-ß, as well as immune cell infiltration in the colon tissues of UC patients. Furthermore, DPP4 was strongly associated with ferroptosis biomarkers, particularly in Subtype 2 of UC. Interestingly, our study also found that DPP4 expression was significantly reduced in RSL3-treated ferroptotic intestinal epithelial cells, more so than in LPS-treated cell models. Inhibition of DPP4 had a significant impact on the expression of ferroptotic biomarkers. Additionally, DPP4 expression was decreased in the colon tissues of DSS-treated mice, and the ferroptosis inhibitor Ferritin-1 effectively counteracted the effects of DSS on immune cell infiltration, colon length, and DPP4 expression. CONCLUSIONS: DPP4 can serve as a biomarker for ferroptosis in the diagnosis and management of UC.

Linagliptin decreased the tumor progression on glioblastoma model.

PURPOSE: Dipeptidyl peptidase-4 (DPP-4) inhibitors are oral hypoglycemic drugs and are used for type II diabetes. Previous studies showed that DPP-4 expression is observed in several tumor types and DPP-4 inhibitors suppress the tumor progression on murine tumor models. In this study, we evaluated the role of DPP-4 and the antitumor effect of a DPP-4 inhibitor, linagliptin, on glioblastoma (GBM). METHODS: We analyzed DPP-4 expression in glioma patients by the public database. We also analyzed DPP-4 expression in GBM cells and the murine GBM model. Then, we evaluated the cell viability, cell proliferation, cell migration, and expression of some proteins on GBM cells with linagliptin. Furthermore, we evaluated the antitumor effect of linagliptin in the murine GBM model. RESULTS: The upregulation of DPP-4 expression were observed in human GBM tissue and murine GBM model. In addition, DPP-4 expression levels were found to positively correlate with the grade of glioma patients. Linagliptin suppressed cell viability, cell proliferation, and cell migration in GBM cells. Linagliptin changed the expression of phosphorylated NF-kB, cell cycle, and cell adhesion-related proteins. Furthermore, oral administration of linagliptin decreases the tumor progression in the murine GBM model. CONCLUSION: Inhibition of DPP-4 by linagliptin showed the antitumor effect on GBM cells and the murine GBM model. The antitumor effects of linagliptin is suggested to be based on the changes in the expression of several proteins related to cell cycle and cell adhesion via the regulation of phosphorylated NF-kB. This study suggested that DPP-4 inhibitors could be a new therapeutic strategy for GBM.

Identification of DPP-IV inhibitory peptides derived from buffalo colostrum: Mining through bioinformatics, in silico and in vitro approaches.

Bioactive peptides derived from foods provide physiological health benefits beyond nutrition. This study focused on profiling small peptide inhibitors against two key serine proteases, dipeptidyl peptidase-IV (DPP-IV) and prolyl oligopeptidase (POP). DPP-IV is a well-known protein involved in diverse pathways regulating inflammation, renal, cardiovascular physiology, and glucose homeostasis. POP is yet another key target protein for neurodegenerative disorders. The study evaluated peptide libraries of buffalo colostrum whey and fat globule membrane proteins derived from pepsin and pepsin-pancreatin digestion through in silico web tools and structure-based analysis by molecular docking and binding free-energy estimation, followed by in vitro assay for DPP-IV inhibition for the lead peptides. The bioinformatic study indicated 49 peptides presented motifs with DPP-IV inhibition while 5 peptides with sequences for POP inhibition. In the molecular docking interactions study, 22 peptides interacted with active site residues of DPP-IV and 3 peptides with that of POP. The synthesized peptides, SFVSEVPEL and LTFQHNF inhibited DPP-IV in vitro with an IC50 of 193.5 µM and 1.782 mM, respectively. The study revealed the key residues for inhibition of DPP-IV and POP thus affirming the DPP-IV inhibitory potential of milk-derived peptides.

Activation of the NLRP1 Inflammasome and Its Role in Transmissible Gastroenteritis Coronavirus Infection.

The inflammasome pathway is a critical early response mechanism of the host that detects pathogens, initiates the production of inflammatory cytokines, and recruits effector cells to the infection site. Nonetheless, the mechanism of inflammasome activation in coronavirus infection and its biological functions in host defense remain unclear. Transmissible gastroenteritis virus (TGEV), a member of the genus Alphacoronavirus, is a significant pathogen that mainly infects piglets and causes intestinal inflammation and inflammatory cell infiltration. Here, we investigated the mechanism of inflammasome activation in intestinal epithelial cells (IECs) infected with TGEV. We observed a substantial increase in interleukin 1ß (IL-1ß) and IL-18 levels in both IECs and TGEV-infected porcine intestinal tissues. Furthermore, TGEV infection resulted in increased activation of caspase-1 and the NLRP1 (NOD-like receptor [NLR]-containing pyrin domain [PYD]) inflammasome. Our findings revealed that TGEV infection impeded the interaction between porcine NLRP1 (pNLRP1) and porcine dipeptidyl peptidases 9 (pDPP9), yet it did not reduce the expression of pDPP9. Importantly, the ZU5 domain, not the function-to-find domain (FIIND) reported in human NLRP1, was identified as the minimal domain of pNLRP1 for pDPP9 binding. In addition, the robust type I IFN expression induced by TGEV infection also upregulated pNLRP1 expression and pNLRP1 itself acts as an interferon-stimulated gene to counteract TGEV infection. Our data demonstrate that pNLRP1 has antiviral capabilities against coronavirus infection, which highlights its potential as a novel therapeutic target for coronavirus antiviral therapy. IMPORTANCE Coronavirus primarily targets the epithelial cells of the respiratory and gastrointestinal tracts, leading to damage in both humans and animals. NLRP1 is a direct sensor for RNA virus infection which is highly expressed in epithelial barrier tissues. However, until recently, the precise molecular mechanisms underlying its activation in coronavirus infection and subsequent downstream events remained unclear. In this study, we demonstrate that the alphacoronavirus TGEV induces the production of IL-1ß and IL-18 and upregulates the expression of pNLRP1. Furthermore, we found that pNLRP1 can serve as an interferon-stimulated gene (ISG) to inhibit the infection of enterovirus TGEV. Our research highlights the crucial role of NLRP1 as a regulator of innate immunity in TGEV infection and shows that it may serve as a potential therapeutic target for the treatment of coronavirus infection.