Mechanism of molecular interaction of sitagliptin with human DPP4 enzyme - New Insights.

PURPOSE: Dipeptidyl peptidase 4 (DPP4) inactivates a range of bioactive peptides. The cleavage of insulinotropic peptides and glucagon-like peptide 1 (GLP1) by DPP4 directly influences glucose homeostasis. This study aimed to describe the mode of interaction between sitagliptin (an antidiabetic drug) and human DPP4 using in silico approaches. MATERIALS AND METHODS: Docking studies were conducted using AutoDock Vina, 2D and 3D schematic drawings were obtained using PoseView and PLIP servers, and the DPP4-sitagliptin complex was visualized with Pymol software. RESULTS: The best affinity energy to form the DPP4-sitagliptin complex was E-value â€‹= â€‹- 8.1 â€‹kcal â€‹mol-1, as indicated by docking simulations. This result suggests a strong interaction. According to our observations, hydrophobic interactions involving the amino acids residues Tyr663 and Val712, hydrogen bonds (Glu203, Glu204, Tyr663, and Tyr667), π-Stacking interactions (Phe355 and Tyr667), and halogenic bonds (Arg123, Glu204, and Arg356) were prevalent in the DPP4-sitagliptin complex. Root Mean Square Deviation prediction also demonstrated that the global structure of the human DPP4 did not have a significant change in its topology, even after the formation of the DPP4-sitagliptin complex. CONCLUSION: The stable interaction between the sitagliptin ligand and the DPP4 enzyme was demonstrated through molecular docking simulations. The findings presented in this work enhance the understanding of the physicochemical properties of the sitagliptin interaction site, supporting the design of more efficient gliptin-like iDPP4 inhibitors.

Targeting adrenergic receptors to mitigate invariant natural killer T cells-induced acute liver injury.

Invariant Natural Killer T (iNKT) cell activation by α-galactosylceramide (αGC) potentiates cytotoxic immune responses against tumors. However, αGC-induced liver injury is a limiting factor for iNKT-based immunotherapy. Although adrenergic receptor stimulation is an important immunosuppressive signal that curbs tissue damage induced by inflammation, its effect on the antitumor activity of invariant Natural Killer T (iNKT) cells remains unclear. We use mouse models and pharmacological tools to show that the stimulation of the sympathetic nervous system (SNS) inhibits αGC-induced liver injury without impairing iNKT cells' antitumoral functions. Mechanistically, SNS stimulation prevents the collateral effect of TNF-α production by iNKT cells and neutrophil accumulation in hepatic parenchyma. Our results suggest that the modulation of the adrenergic signaling can be a complementary approach to αGC-based immunotherapy to mitigate iNKT-induced liver injury without compromising its antitumoral activity.

Tissue-specific metabolic profile drives iNKT cell function during obesity and liver injury.

Invariant natural killer T (iNKT) cells are a distinct population of lymphocytes characterized by their reactivity to glycolipids presented by CD1d. iNKT cells are found throughout the body, and little is known about their tissue-specific metabolic regulation. Here, we show that splenic and hepatic iNKT cells are metabolically comparable and rely on glycolytic metabolism to support their activation. Deletion of the pyruvate kinase M2 (Pkm2) gene in splenic and hepatic iNKT cells impairs their response to specific stimulation and their ability to mitigate acute liver injury. In contrast, adipose tissue (AT) iNKT cells exhibit a distinctive immunometabolic profile, with AMP-activated protein kinase (AMPK) being necessary for their function. AMPK deficiency impairs AT-iNKT physiology, blocking their capacity to maintain AT homeostasis and their ability to regulate AT inflammation during obesity. Our work deepens our understanding on the tissue-specific immunometabolic regulation of iNKT cells, which directly impacts the course of liver injury and obesity-induced inflammation.

New insights about the EptA protein and its correlation with the pmrC gene in polymyxin resistance in Pseudomonas aeruginosa.

Nowadays, clinical and scientific interest in antibiotics, as polymyxin, has increased due to the large number of reports of multiresistant Gram-negative bacteria, as Pseudomonas aeruginosa. The aim of this study was to investigate a related group of proteins for resistance to polymyxins, encoded by P. aeruginosa genome, through in silico analysis. The mobilized colistin resistance 1 (MCR1) protein from Escherichia coli was used for comparison. Similar sequences to the protein MCR1 in P. aeruginosa were analysed for physicochemical properties. 31 protein isoforms in P. aeruginosa (EptA) were found able to confer resistance to polymyxin showing protein lengths between 551 and 572 amino acids, with molecular mass values between 61.36 - 62. 80 kDa, isoelectric point between 6.10 to 7.17, instability index between 33.76 to 41.87, aliphatic index between 98.67 to 102.63 and the hydropathyindex between - 0.008 to 0.094. These proteins belong to the DUF1705 superfamily with bit-score values between 559.81 and 629.78. A high degree of similarity between EpTAs in P. aeruginosa was observed in relation to other proteins that confer resistance to polymyxins, present in Gram-negative bacteria species of clinical interest. Although, further studies are needed to identify the actual contribution of EptAs in P. aeruginosa species.

Nano spray dryer for vectorizing α-galactosylceramide in polymeric nanoparticles: A single step process to enhance invariant Natural Killer T lymphocyte responses.

The recognition of α-galactosylceramide (αGC), a high-affinity CD1d antigen, by the invariant Natural Killer T (iNKT) lymphocytes results in potent immunostimulatory responses that have been exploited in advanced cancer patients. Therefore, to improve αGC biological activity, several studies vectorized this agonist in PLGA and/or PEG-based nanoparticles. Despite promising findings, these approaches require several steps, from organic solvent decontamination through extrusion in membrane systems. Using a nano spray dryer, we vectorized αGC into a cationic copolymer (dimethylaminoethyl methacrylate, butyl methacrylate and methyl methacrylate - DBM) in a single step process, free of organic solvent. This methodology allowed the production of stable αGC-vectorized nanoparticles (DBM + αGC) with a more potent biological activity than the free agonist. DBM nanoparticles improved in vivo αGC loading into the CD1d molecule and induced a higher frequency of IFN-γ-expressing iNKT cells. Consequently, mice treated with DBM + αGC presented higher levels of serum IFN-γ than those treated with free agonist. Also, vectorized nanoparticles improved αGC ability to control the growth of murine lung metastatic carcinoma. Thus, this is the first study showing that nano spray dryer technology is a simple and alternative approach to enhance iNKT responses.