Linagliptin inhibits lipopolysaccharide-induced inflammation in human U937 monocytes

In Silico Drug Repurposing for Anti-Inflammatory Therapy: Virtual Search for Dual Inhibitors of Caspase-1 and TNF-Alpha

Inflammation involves a complex biological response of the body tissues to damaging stimuli. When dysregulated, inflammation led by biomolecular mediators such as caspase-1 and tumor necrosis factor-alpha (TNF-alpha) can play a detrimental role in the progression of different medical conditions such as cancer, neurological disorders, autoimmune diseases, and cytokine storms caused by viral infections such as COVID-19. Computational approaches can accelerate the search for dual-target drugs able to simultaneously inhibit the aforementioned proteins, enabling the discovery of wide-spectrum anti-inflammatory agents. This work reports the first multicondition model based on quantitative structure–activity relationships and a multilayer perceptron neural network (mtc-QSAR-MLP) for the virtual screening of agency-regulated chemicals as versatile anti-inflammatory therapeutics. The mtc-QSAR-MLP model displayed accuracy higher than 88%, and was interpreted from a physicochemical and structural point of view. When using the mtc-QSAR-MLP model as a virtual screening tool, we could identify several agency-regulated chemicals as dual inhibitors of caspase-1 and TNF-alpha, and the experimental information later retrieved from the scientific literature converged with our computational results. This study supports the capabilities of our mtc-QSAR-MLP model in anti-inflammatory therapy with direct applications to current health issues such as the COVID-19 pandemic.

Linagliptin Inhibits Interleukin-6 Production Through Toll-Like Receptor 4 Complex and Lipopolysaccharide-Binding Protein Independent Pathway in vitro Model

Purpose

Lipopolysaccharides (LPS) induce inflammation by binding to the Toll-like receptor (TLR) 4 complex, including LPS-binding protein (LBP). The anti-inflammatory effects of linagliptin in LPS-induced inflammation in the TLR4-independent pathway have not been examined before. We examined the anti-inflammatory effects of linagliptin in the TLR4- and the LBP-independent pathway.

Methods

U937 cells were cultured in the medium supplemented with 10% fetal bovine serum (FBS) and treated with 100 nM phorbol myristate acetate for 48 h. Cells were then left untreated or were treated with 10 μg/mL anti-TLR4 antibodies alone or in combination with linagliptin for 1 h in media supplemented with or without 10% FBS. The cells were divided into 5 groups: a) control cells (untreated) b) cells treated with LPS c) cells treated with 10 μg/mL anti-TLR4 antibodies d) cells treated with LPS and 10 μg/mL anti-TLR4 antibodies and e) cells treated with LPS, 10 μg/mL anti-TLR4 antibodies, and linagliptin. The LPS concentrations used were 50 pg/mL or 100 pg/mL for cells treated in the presence of 10% FBS and 100 pg/mL or 1 μg/mL for cells treated in the absence of FBS. Linagliptin concentrations of 1 nM, 10 nM, and 100 nM were used for treatment. The supernatants were analyzed for interleukin (IL)-6 production after 24 h of various treatments.

Results

LPS increased IL-6 production compared to the untreated control cells, and anti-TLR4 antibody suppressed LPS-induced increased IL-6 levels. Linagliptin suppressed LPS-induced IL-6 production in a concentration-dependent manner in the presence of FBS. However, only 100 nM linagliptin could suppress LPS-induced IL-6 production in the absence of FBS.

Conclusion

Concentration-dependent and -independent inflammatory suppression was observed following linagliptin treatment after LPS induction in an experimental model of TLR4 inhibition by anti-TLR4 antibodies. Our results showed that linagliptin may inhibit inflammation through multiple mechanisms centered around the TLR-4-mediated pathway.

Effects of Incretin-Related Diabetes Drugs on Bone Formation and Bone Resorption

Patients with type 2 diabetes have an increased risk of fracture compared to the general population. Glucose absorption is accelerated by incretin hormones, which induce insulin secretion from the pancreas. The level of the incretin hormone, glucagon-like peptide-1 (GLP-1), shows an immediate postprandial increase, and the circulating level of intact GLP-1 is reduced rapidly by dipeptidyl peptidase-4 (DPP-4)-mediated inactivation. Therefore, GLP-1 receptor agonists and DPP-4 inhibitors are effective in the treatment of type 2 diabetes. However, these incretin-related diabetic agents have been reported to affect bone metabolism, including bone formation and resorption. These agents enhance the expression of bone markers, and have been applied to improve bone quality and bone density. In addition, they have been reported to suppress chronic inflammation and reduce the levels of inflammatory cytokine expression. Previously, we reported that these incretin-related agents inhibited both the expression of inflammatory cytokines and inflammation-induced bone resorption. This review presents an overview of current knowledge regarding the effects of incretin-related diabetes drugs on osteoblast differentiation and bone formation as well as osteoclast differentiation and bone resorption. The mechanisms by which incretin-related diabetes drugs regulate bone formation and bone resorption are also discussed.

Prognostic roles of diabetes mellitus and hypertension in advanced hepatocellular carcinoma treated with sorafenib

BACKGROUND & AIMS

It remains limited whether diabetes mellitus (DM) and hypertension (HTN) affect the prognosis of advanced hepatocellular carcinoma (HCC) treated with sorafenib. Our study attempted to elucidate the roles of DM/HTN and the effects of diabetes medications among advanced HCC patients receiving sorafenib.

METHODS

From August 2012 to February 2018, 733 advanced HCC patients receiving sorafenib were enrolled at China Medical University, Taichung, Taiwan. According to the presence/absence of DM or HTN, they were divided into four groups: control [DM(-)/HTN(-), n = 353], DM-only [DM(+)/HTN(-), n = 91], HTN-only [DM(-)/HTN(+), n = 184] and DM+HTN groups [DM(+)/HTN(+), n = 105]. Based on the types of diabetes medications, there were three groups among DM patients (the combined cohort of DM-only and DM+HTN groups), including metformin (n = 63), non-metformin oral hypoglycemic agent (OHA) (n = 104) and regular insulin (RI)/neutral protamine hagedorn (NPH) groups (n = 29). We then assessed the survival differences between these groups.

RESULTS

DM-only and DM+HTN groups significantly presented longer overall survival (OS) than control group (control vs. DM-only, 7.70 vs. 11.83 months, p = 0.003; control vs. DM+HTN, 7.70 vs. 11.43 months, p = 0.008). However, there was no significant OS difference between control and HTN-only group (7.70 vs. 8.80 months, p = 0.111). Besides, all groups of DM patients showed significantly longer OS than control group (control vs. metformin, 7.70 vs. 12.60 months, p = 0.011; control vs. non-metformin OHA, 7.70 vs. 10.80 months, p = 0.016; control vs. RI/NPH, 7.70 vs. 15.20 months, p = 0.026).

CONCLUSIONS

Rather than HTN, DM predicts better prognosis in advanced HCC treated with sorafenib. Besides, metformin, non-metformin OHA and RI/NPH are associated with longer survival among DM-related advanced HCC patients receiving sorafenib.

DPP-4 Inhibitor Linagliptin Ameliorates Oxidized LDL-Induced THP-1 Macrophage Foam Cell Formation and Inflammation

Introduction

Atherosclerosis is one of the major causes of cardiovascular diseases. Lipid uptake and accumulation in macrophages play a major role in atherosclerotic plaque formation from its initiation to advanced atheroma formation. The dipeptidyl peptidase-4 (DPP-4) inhibitor Linagliptin is commonly used to lower blood glucose in type 2 diabetes patients. Recent studies report that Linagliptin has cardiovascular protective and anti-inflammatory effects.

Methods

THP-1 macrophage cells were treated with 100 nM PMA for 72 hour to induce foam cell formation. The differentiated cells were exposed to 100 μg/mL ox-LDL in the presence or absence of the DPP-4 inhibitor Linagliptin. The expression levels of DPP-4 and inflammatory cytokines were detected by RT-PCR, ELISA, and Western blot experiments. The cellular ROS level was measured by staining the cells with the fluorescent probe DCFH-DA. The separation of lipoprotein fractions was achieved by high-performance liquid chromatography (HPLC). The cells were labeled with fluorescent-labeled cholesterol to measure cholesterol efflux, and lipid droplets were revealed by Nile red staining.

Results

The presence of Linagliptin significantly reduced ox-LDL-induced cytokine production (IL-1β and IL-6) and ROS production. Linagliptin ameliorated ox-LDL-induced lipid accumulation and impaired cholesterol efflux in macrophages. Mechanistically, this study showed that Linagliptin mitigated ox-LDL-induced expression of the scavenger receptors CD36 and LOX-1, but not SRA. Furthermore, Linagliptin increased the expression of the cholesterol transporter ABCG1, but not ABCA1.

Conclusion

Linagliptin possesses a potent inhibitory effect on THP-1 macrophage-derived foam cell formation in response to ox-LDL. This effect could be mediated through a decrease in the expression of CD36 and LOX-1 on macrophages and an increase in the expression of the cholesterol transporter ABCG1. This study indicates that the DPP-4 inhibitor Linagliptin plays a critical role in preventing foam cell formation in vitro. However, future research using an atherosclerotic animal model is necessary to determine its effectiveness and to prove its potential implication in the prevention and treatment of atherosclerosis.

Effect of a DPP-4 Inhibitor on Orthodontic Tooth Movement and Associated Root Resorption

Objectives

Dipeptidyl peptidase-4 (DPP-4) inhibitors are used as a treatment for type 2 diabetes mellitus and have also recently been applied to enhance bone quality and density, and increase the expression of bone markers. This study aimed to investigate the effect of a DPP-4 inhibitor on orthodontic tooth movement (OTM) and related root resorption in a mouse model.

Materials and Methods

Mice were randomly divided into three groups: those undergoing OTM with the addition of a DPP-4 inhibitor (30 μg), those undergoing OTM and receiving phosphate-buffered saline (PBS), and those without force loading (control group). OTM was achieved by means of a nickel-titanium closed coil spring that moved the first molar in a mesial direction for 12 days. The distance of OTM was measured using silicone impression. Maxillae were removed for histological analysis or real-time PCR analysis.

Results

The distance of OTM and the number of osteoclasts were significantly decreased after administration of the DPP-4 inhibitor, which also significantly suppressed the number of odontoclasts and root resorption after OTM. Furthermore, the mRNA expression of tumour necrosis factor-α (TNF-α) and the receptor activator of nuclear factor kappa-B ligand (RANKL) were decreased in DPP-4 inhibitor-treated mice compared with those receiving PBS and control animals.

Conclusion

The DPP-4 inhibitor inhibited tooth movement and associated root resorption by blocking the formation of osteoclasts and odontoclasts, respectively. It also appeared to inhibit osteoclastogenesis and odontoclastogenesis by suppressing the expression of TNF-α and/or RANKL.

Linagliptin protects human chondrogenic ATDC5 cells against advanced glycation end products (AGEs)-induced apoptosis via a mitochondria-dependent pathway

Chondrocytes in joints are responsible for the formation and remodeling of articular cartilage. The accumulation of advanced glycation end products (AGEs) in cartilage is detrimental to the survival of chondrocytes. Linagliptin is one of the most commonly used anti-diabetes agents, and recent work indicates that it exerts an anti-inflammatory effect in different cell types. In this study, we showed that Linagliptin had a protective role in AGEs-induced chondrocyte injury. The presence of Linagliptin ameliorated AGEs-induced reactive oxygen species (ROS) induction and reduced cellular protein carboxyl content. Linagliptin mitigated AGEs-induced mitochondrial membrane potential (_ΔΨm) reduction and NAPDH oxidase subunit NOX-4 induction, indicating that Linagliptin is a potent anti-ROS agent in chondrocytes. Additionally, Linagliptin inhibited AGEs-induced production of high mobility group box chromosomal protein 1 (HMGB-1), and the expression of matrix metalloproteases (MMPs)-2 and -9. Flow cytometry experimentation showed that Linagliptin inhibited AGEs-induced apoptotic subpopulation. Moreover, Linagliptin inhibited the AGEs-induced increased ratio of Bax to Bcl-2, translocation of cytochrome C from mitochondria to the cytoplasm, and release of cleaved caspase-3. Collectively, our data indicate that the anti-diabetes drug Linagliptin has a new role in rescuing chondrocyte from insult by AGEs, and may, therefore, have the potential to treat joint disorders.

Linagliptin Inhibits Lipopolysaccharide-Induced Inflammation Concentration-Dependently And -Independently

Purpose

Dipeptidyl peptidase-4 inhibitors, including linagliptin, prevent inflammation. However, the in vitro effects of linagliptin are unclear. Moreover, although linagliptin inhibits lipopolysaccharide (LPS)-induced inflammation, the anti-inflammatory effects of linagliptin in this context are not concentration-dependent. In the absence of LPS-binding protein (LBP), the pro-inflammatory effects of LPS involve pathways other than the Toll-like receptor (TLR) 4 pathway. Here, we aimed to determine the anti-inflammatory mechanisms of linagliptin in an experimental model in which LBP was added to the medium.

Methods

Human U937 monocytes were cultured at 1 × 10⁶ cells/mL in Roswell Park Memorial Institute medium and differentiated into macrophages using phorbol myristate acetate. All processes were carried out in medium containing 10% fetal bovine serum (FBS). After 48 hrs of culture, we replaced the medium and pretreated the cells with 100, 250, 500, or 2500 nM linagliptin for 1 hr. We exchanged the medium again, and the cells were treated with 1 ng/mL LPS with or without 100, 250, 500, or 2500 nM linagliptin. Interleukin (IL)-6 and LBP in the supernatant, nuclear factor (NF)-κB/p65 in the nucleus, and reactive oxygen species (ROS) in the cells, as important markers of the mechanism of inflammation induction by LPS, were measured using enzyme-linked immunosorbent assay kits.

Results

Linagliptin significantly prevented LPS-stimulated IL-6 production and intranuclear NF-κB/p65 levels in a concentration-dependent manner. LPS-induced intracellular ROS levels were significantly decreased by linagliptin at all concentrations. LBP levels were markedly higher in FBS-containing medium than in medium without FBS. However, LBP levels did not change following administration of linagliptin and/or LPS.

Conclusion

Concentration-dependent and -independent inflammatory suppression was observed following linagliptin treatment in the context of LPS-induced pro-inflammatory responses. Thus, our findings suggested that linagliptin induced two different mechanisms to repress inflammation, i.e., TLR4-dependent and -independent mechanisms.

Neuroprotective Properties of Linagliptin: Focus on Biochemical Mechanisms in Cerebral Ischemia, Vascular Dysfunction and Certain Neurodegenerative Diseases

Linagliptin is a representative of dipeptidyl peptidase 4 (DPP-4) inhibitors which are registered and used effectively in a treatment of diabetes mellitus type 2. They increase the levels of active forms of endogenous incretins such as GLP-1 and GIP by inhibiting their enzymatic decomposition. Scientific reports suggest beneficial effects of linagliptin administration via immunological and biochemical pathways involved in neuroprotective processes of CNS. Linagliptin’s administration leads to a decrease in the concentration of proinflammatory factors such as: TNF-α, IL-6 and increases the number of anti-inflammatory patrolling monocytes CX3CR1^bright. Significant reduction in Aβ42 level has been associated with the use of linagliptin implying potential application in Alzheimer’s disease. Linagliptin improved vascular functions by increasing production of nitric oxide (NO) and limiting concentration of apolipoprotein B. Linagliptin-induced decrease in macrophages infiltration may provide improvement in atheromatous plaque stabilization. Premedication with linagliptin increases neuron’s survival after stroke and augments neuronal stem cells proliferation. It seems to be connected with SDF-1α/CXCR4 signaling pathway. Linagliptin prevented abnormal proliferation and migration of rat brain microvascular endothelial cells in a state of hypoperfusion via SIRT1/HIF-1α/VEGF pathway. The article presents a summary of the studies assessing neuroprotective properties of linagliptin with special emphasis on cerebral ischemia, vascular dysfunction and neurodegenerative diseases.

Klotho Ameliorates Cellular Inflammation via Suppression of Cytokine Release and Upregulation of miR-29a in the PBMCs of Diagnosed Alzheimer's Disease Patients

Alzheimer's disease (AD) is the most common neurodegenerative disorder characterized by neural inflammation and oxidative stress. In the current study, the protective effects of klotho and linagliptin treatment on human peripheral blood mononuclear cells (PBMCs) of AD patients and healthy controls (HCs) are assessed through measurement of inflammatory cytokines, signaling proteins, and miRNA expression. Sixteen diagnosed AD patients and sixteen HCs were enrolled in the study. Blood samples were obtained and PBMCs were isolated. PBMCs were treated with klotho at different concentrations (0.5, 1, and 2 nM) and linagliptin (50 μM). The concentration of interleukin-1β (IL-1β), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), epsilon isoform of protein kinase C (PKCε), phosphorylated cyclic AMP response element binding (pCREB), and Wnt1 were measured by ELISA. The expression of miR-29a and miR-195 was detected by real-time PCR. The results showed that klotho significantly reduced IL-1β, IL-6, and TNF-α levels in both groups of the experiment. Linagliptin also remarkably reduced TNF-α levels in the AD group. Moreover, klotho caused the downregulation of Wnt1 in the PBMCs of both groups and the upregulation of the pCREB in HCs. Meanwhile, klotho induced miR-29a expression in the PBMCs of HCs, while miR-29a expression was induced in the AD group by klotho and linagliptin. The current findings revealed that klotho alleviates inflammation in human PBMCs, probably through the suppression of inflammatory cytokines and the upregulation of miR-29a, and part of its beneficial effect is mediated through appropriate modulation of the Wnt1/pCREB signaling cascade. In addition, linagliptin exerts protective effects by reducing TNF-α and inducing miR-29a expression in PBMCs.

Vascular protection of DPP-4 inhibitors in retinal endothelial cells in in vitro culture

People with diabetes are at high risk of developing diabetes-related eye disease, termed as diabetic retinopathy, due damage being caused to the blood vessels in the retina. An efficient medical treatment to reduce diabetic retinopathy can improve the quality of life for diabetes patients. In our study, we show that linagliptin, a commercially available DPP-4 inhibitor, plays a protective role in retinal vascular endothelial cells. The presence of linagliptin protects retinal endothelial cells against TNF-α-induced cytotoxicity and enhances their viability. Linagliptin treatment suppresses TNF-α-induced production of reactive oxygen species and improves mitochondrial membrane potential. Moreover, linagliptin suppresses TNF-α-induced production of pro-inflammatory and pro-adhesive vascular cytokines including IL-6, IL-8, ICAM-1, and VCAM-1. The presence of linagliptin in cell media can reduce the number of THP-1 cells that adhere to retina endothelial cells. Mechanistically, linagliptin potently suppresses TNF-α-induced accumulation of NF-κB nuclear protein p65 and activation of NF-κB promoter. Our data indicate that linagliptin is an anti-inflammatory diabetic agent, with the potential to be applied as a treatment for diabetic retinopathy.