DPP4 inhibition by sitagliptin attenuates LPS-induced lung injury in mice

Endothelial knockdown of the tumor suppressor, WWOX, increases inflammation in ventilator-induced lung injury

Chronic cigarette smoke exposure decreases lung expression of WWOX which is known to protect the endothelial barrier during infectious models of acute respiratory distress syndrome (ARDS). Proteomic analysis of WWOX-silenced endothelial cells (ECs) was done using tandem mass tag mass spectrometry (TMT-MS). WWOX-silenced ECs as well as those isolated from endothelial cell Wwox knockout (EC Wwox KO) mice were subjected to cyclic stretch (18% elongation, 0.5 Hz, 4 h). Cellular lysates and media supernatant were harvested for assays of cellular signaling, protein expression, and cytokine release. These were repeated with dual silencing of WWOX and zyxin. Control and EC Wwox KO mice were subjected to high tidal volume ventilation. Bronchoalveolar lavage fluid and mouse lung tissue were harvested for cellular signaling, cytokine secretion, and histological assays. TMT-MS revealed upregulation of zyxin expression during WWOX knockdown which predicted a heightened inflammatory response to mechanical stretch. WWOX-silenced ECs and ECs isolated from EC Wwox mice displayed significantly increased cyclic stretch-mediated secretion of various cytokines (IL-6, KC/IL-8, IL-1β, and MCP-1) relative to controls. This was associated with increased ERK and JNK phosphorylation but decreased p38 mitogen-activated kinases (MAPK) phosphorylation. EC Wwox KO mice subjected to VILI sustained a greater degree of injury than corresponding controls. Silencing of zyxin during WWOX knockdown abrogated stretch-induced increases in IL-8 secretion but not in IL-6. Loss of WWOX function in ECs is associated with a heightened inflammatory response during mechanical stretch that is associated with increased MAPK phosphorylation and appears, in part, to be dependent on the upregulation of zyxin.NEW & NOTEWORTHY Prior tobacco smoke exposure is associated with an increased risk of acute respiratory distress syndrome (ARDS) during critical illness. Our laboratory is investigating one of the gene expression changes that occurs in the lung following smoke exposure: WWOX downregulation. Here we describe changes in protein expression associated with WWOX knockdown and its influence on ventilator-induced ARDS in a mouse model.

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.

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.

Functional Roles of CD26/DPP4 in Bleomycin-Induced Pulmonary Hypertension Associated with Interstitial Lung Disease

Pulmonary hypertension (PH) with interstitial lung diseases (ILDs) often causes intractable conditions. CD26/Dipeptidyl peptidase-4 (DPP4) is expressed in lung constituent cells and may be related to the pathogenesis of various respiratory diseases. We aimed to clarify the functional roles of CD26/DPP4 in PH-ILD, paying particular attention to vascular smooth muscle cells (SMCs). Dpp4 knockout (Dpp4KO) and wild type (WT) mice were administered bleomycin (BLM) intraperitoneally to establish a PH-ILD model. The BLM-induced increase in the right ventricular systolic pressure and the right ventricular hypertrophy observed in WT mice were attenuated in Dpp4KO mice. The BLM-induced vascular muscularization in small pulmonary vessels in Dpp4KO mice was milder than that in WT mice. The viability of TGFβ-stimulated human pulmonary artery SMCs (hPASMCs) was lowered due to the DPP4 knockdown with small interfering RNA. According to the results of the transcriptome analysis, upregulated genes in hPASMCs with TGFβ treatment were related to pulmonary vascular SMC proliferation via the Notch, PI3K-Akt, and NFκB signaling pathways. Additionally, DPP4 knockdown in hPASMCs inhibited the pathways upregulated by TGFβ treatment. These results suggest that genetic deficiency of Dpp4 protects against BLM-induced PH-ILD by alleviating vascular remodeling, potentially through the exertion of an antiproliferative effect via inhibition of the TGFβ-related pathways in PASMCs.

Anti-inflammatory and antinociceptive effects of sitagliptin in animal models and possible mechanisms involved in the antinociceptive activity

Background

Sitagliptin is an antidiabetic drug that inhibits dipeptidyl peptidase-4 enzyme. This study aimed to investigate the antinociceptive and anti-inflammatory effects of sitagliptin in formalin and carrageenan tests and determine the possible mechanism(s) of its antinociceptive activity.

Methods

Male Swiss mice (25-30 g) and male Wistar rats (180-220 g) were used for formalin and carrageenan tests, respectively. In the formalin test, paw licking time and in the carrageenan test, paw thickness were considered as indexes of pain behavior and inflammation respectively. Three doses of sitagliptin (2.5, 5, and 10 mg/kg) were used in these tests. Also, several antagonists and enzyme inhibitors were used to evaluate the role of adrenergic, serotonergic, dopaminergic, and opioid receptors as well as the NO/cGMP/KATP pathway in the antinociceptive effect of sitagliptin (5 mg/kg).

Results

Sitagliptin showed significant antinociceptive and anti-inflammatory effects in the formalin and carrageenan tests respectively. In the carrageenan test, all three doses of sitagliptin significantly (P < 0.001) reduced paw thickness. Pretreatment with yohimbine, prazosin, propranolol, naloxone, and cyproheptadine could not reverse the antinociceptive effect of sitagliptin (5 mg/Kg), which indicates that adrenergic, opioid, and serotonin receptors (5HT2) are not involved in the antinociceptive effects. L-NAME, methylene blue, glibenclamide, ondansetron, and sulpiride were able to reverse this effect.

Conclusions

NO/cGMP/KATP, 5HT3 and D2 pathways play an important role in the antinociceptive effect of sitagliptin. Additionally significant anti-inflammatory effects observed in the carrageenan test might contribute in reduction of pain response in the second phase of the formalin test.

Ugonin P inhibits lung cancer motility by suppressing DPP-4 expression via promoting the synthesis of miR-130b-5p

Lung cancer is the leading cause of cancer-related death worldwide, and the survival rate of metastatic lung cancer is exceedingly low. Helminthostatchys Zeylanica (H. Zeylanica) is a Chinese herbal medicine renowned for its anti-inflammatory, immunomodulatory, and anti-cancer activities in various cellular and animal studies. The current study evaluated the effects of H. Zeylanica derivatives on lung cancer cells. We determined that dipeptidyl peptidase-4 (DPP-4) expression levels were higher in lung cancer tissues than in normal tissues. We also determined that DPP-4 expression levels were higher in the metastatic stage and strongly correlated with lung cancer survival rates. An H. Zeylanica derivative (ugonin P) was shown to inhibit DPP-4 mRNA and protein expression in two lung cancer cell lines in a dose-dependent manner. Ugonin P was shown to decrease migration and invasion activities in lung cancer cells while promoting the synthesis of miR-130b-5p, which was found to negatively regulate DPP-4 protein expression and cell motility in lung cancer. We determined that ugonin P suppresses the DPP-4-dependent migration and invasion of lung cancer cells by downregulating the RAF/MEK/ERK signalling pathway and enhancing the expression of miR-130b-5p. This study provides compelling evidence that ugonin P could be used to develop novel therapeutic agents for the treatment of lung cancer.

Glucose metabolism disorder: a potential accomplice of SARS-CoV-2

Globally, 265,713,467 confirmed cases of SARS-CoV-2 (CoV-2), including 5,260,888 deaths, have been reported by the WHO. It is important to study the mechanism of this infectious disease. A variety of evidences show the potential association between CoV-2 and glucose metabolism. Notably, people with type 2 diabetes mellitus (T2DM) and other metabolic complications were prone to have a higher risk of developing a more severe infection course than people who were metabolically normal. The correlations between glucose metabolism and CoV-2 progression have been widely revealed. This review will discuss the association between glucose metabolism disorders and CoV-2 progression, showing the promoting effect of diabetes and other diseases related to glucose metabolism disorders on the progression of CoV-2. We will further conclude the effects of key proteins and pathways in glucose metabolism regulation on CoV-2 progression and potential interventions by targeting glucose metabolism disorders for CoV-2 treatment. Therefore, this review will provide systematic insight into the treatment of CoV-2 from the perspective of glucose metabolism.

Sitagliptin ameliorates busulfan-induced pulmonary and testicular injury in rats through antioxidant, anti-inflammatory, antifibrotic, and antiapoptotic effects

Busulfan (BUS) is an anticancer agent with serious adverse effects on various body organs, including the lung and testis. Sitagliptin was proven to have antioxidant, anti-inflammatory, antifibrotic, and antiapoptotic effects. This study aims to evaluate whether sitagliptin, a DPP4I, ameliorates BUS-induced pulmonary and testicular injury in rats. Male Wistar rats were split into control, sitagliptin (10 mg/kg), BUS (30 mg/kg), and sitagliptin + BUS groups. Weight change, lung and testis indices, serum testosterone, sperm parameters, markers of oxidative stress [malondialdehyde (MDA) and reduced glutathione (GSH)], inflammation [tumor necrosis factor-alpha (TNF-α)], and relative expression of sirtuin1 (SIRT1) and forkhead box protein type O1 (FOXO1) genes were estimated. Histopathological examination of lung and testicular tissues was done to detect architectural changes [Hematoxylin & Eosin (H&E)], fibrosis (Masson's trichrome), and apoptosis (caspase-3). Sitagliptin treatment reduced body weight loss, lung index, lung and testis MDA, serum TNF-α and sperm abnormal morphology, and increased testis index, lung and testis GSH, serum testosterone, sperm count, viability and motility. SIRT1/FOXO1 balance was restored. Also, sitagliptin attenuated fibrosis and apoptosis in lung and testicular tissues via reducing collagen deposition and caspase-3 expression. Accordingly, sitagliptin ameliorated BUS-induced pulmonary and testicular damage in rats via attenuating oxidative stress, inflammation, fibrosis, and apoptosis.

COVID-19 therapeutics: Clinical application of repurposed drugs and futuristic strategies for target-based drug discovery

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) causes the complicated disease COVID-19. Clinicians are continuously facing huge problems in the treatment of patients, as COVID-19-specific drugs are not available hence the principle of drug repurposing serves as a one-and-only hope. Globally, the repurposing of many drugs is underway; few of them are already approved by the regulatory bodies for their clinical use and most of them are in different phases of clinical trials. Here in this review, our main aim is to discuss in detail the up-to-date information on the target-based pharmacological classification of repurposed drugs, the potential mechanism of actions, and the current clinical trial status of various drugs which are under repurposing since early 2020. At last, we briefly proposed the probable pharmacological and therapeutic drug targets that may be preferred as a futuristic drug discovery approach in the development of effective medicines.

Current management of diabetes patients with COVID-19

INTRODUCTION

Diabetes mellitus (DM) and the 2019 coronavirus (COVID-19) appear to interact in both directions. There is mounting proof that patients with DM have a worse COVID-19 prognosis than those without it. Pharmacotherapy is also known to affect in view of the possible interplay between drugs and the pathophysiology of the above conditions in a given patient.

AREAS COVERED

In this review, we discuss the pathogenesis of COVID-19 and its connections with diabetes mellitus. We also analyze the treatment modalities for COVID-19 and diabetes patients. The possible mechanisms of the different medications and their management limitations are also systematically reviewed.

EXPERT OPINION

COVID-19 management as well as its knowledge base is changing constantly. The Pharmacotherapy and the choice of drugs also need to be specifically considered in view of the concomitant presence of these conditions in a patient. Anti-diabetic agents must be carefully evaluated in diabetic patients in view of the disease's severity, blood glucose level, appropriate treatment, and other components that could aggravate adverse events. A methodical technique is anticipated to enable the safe and rational use of drug therapy in COVID-19-positive diabetic patients to take.

Aggressive alternative splicing events discovered in cecum ligation and puncture induced lung injury

AIMS

Acute lung injury (ALI) induced by sepsis and its complications have high morbidity and mortality rates globally. The objective of this study was to enhance our understanding of the underlying mechanism of ALI by identifying potential splicing events that are regulated in this condition.

MATERIALS AND METHODS

The CLP mouse model was utilized for mRNA sequencing, and the expression and splicing data were analyzed. Verification of the changes in expression and splicing induced by CLP was conducted using qPCR and RT-PCR.

RESULTS

Our results showed that splicing-related genes were regulated, suggesting that splicing regulation may be a key mechanism in ALI. We also found that more than 2900 genes displayed alternative splicing in the lungs of mice with sepsis. Using RT-PCR, we verified that TLR4 and other genes had differential splicing isoforms in the lungs of mice with sepsis. We confirmed the presence of TLR4-s in the lungs of mice with sepsis using RNA-fluorescence in situ hybridization.

CONCLUSION

Our results suggest that sepsis-induced ALI can significantly alter splicing in the lungs of mice. The list of DASGs and splicing factors is valuable for further study in the search for new treatment approaches for sepsis-induced ALI.

Current management of diabetes patients with COVID-19

INTRODUCTION

Diabetes mellitus (DM) and the 2019 coronavirus (COVID-19) appear to interact in both directions. There is mounting proof that patients with DM have a worse COVID-19 prognosis than those without it. Pharmacotherapy is also known to affect in view of the possible interplay between drugs and the pathophysiology of the above conditions in a given patient.

AREAS COVERED

In this review, we discuss the pathogenesis of COVID-19 and its connections with diabetes mellitus. We also analyze the treatment modalities for COVID-19 and diabetes patients. The possible mechanisms of the different medications and their management limitations are also systematically reviewed.

EXPERT OPINION

COVID-19 management as well as its knowledge base is changing constantly. The Pharmacotherapy and the choice of drugs also need to be specifically considered in view of the concomitant presence of these conditions in a patient. Anti-diabetic agents must be carefully evaluated in diabetic patients in view of the disease's severity, blood glucose level, appropriate treatment, and other components that could aggravate adverse events. A methodical technique is anticipated to enable the safe and rational use of drug therapy in COVID-19-positive diabetic patients to take.

DPP-4 Inhibitors as a savior for COVID-19 patients with diabetes

Diabetic patients are at particular risk of severe COVID-19. Human dipeptidyl peptidase-4 (DPP-4) is a membrane-bound aminopeptidase that regulates insulin release by inactivating incretin. DPP-4 inhibitors (DPP-4is) are therefore used as oral anti-diabetic drugs to restore normal insulin levels. These molecules also have anti-inflammatory and anti-hypertension effects. Recent studies on the interactions of SARS-CoV-2 spike glycoprotein and DPP-4 predict a possible entry route for SARS-CoV-2. Therefore, DPP-4is could be effective at reducing the virus-induced 'cytokine storm', thereby ceasing inflammatory injury to vital organs. Moreover, DPP-4is may interfere with viral entry into host cells. Herein, we have reviewed the efficacy of DPP-4is as potential repurposed drugs to reduce the severity of SARS-CoV-2 infection in patients with diabetes.

Dipeptidyl peptidase 4 inhibitors in COVID-19: Beyond glycemic control

Coronavirus disease 2019 (COVID-19) is associated with a high risk of mortality and complications in patients with diabetes mellitus. Achieving good glycemic control is very important in diabetic patients to reduce complications and mortality due to COVID-19. Recent studies have shown the mortality benefit and anti-inflammatory effects of Dipeptidyl-peptidase-4 inhibitors (DPP-4i) in diabetic patients with COVID-19. DPP-4i may have a beneficial role in halting the severity of infection primarily by three routes, namely viral entry inhibition, anti-inflammatory and anti-fibrotic effects and glycemic control. This has raised the pro-mising hypothesis that DPP-4i might be an optimal strategy for treating COVID-19 in patients with diabetes. This review aims to summarise the possible therapeutic non-glycemic effects of DPP-4i in diabetic patients diagnosed with COVID-19 in the light of available evidence.

Potential Therapeutic Benefits of Metformin Alone and in Combination with Sitagliptin in the Management of Type 2 Diabetes Patients with COVID-19

Type 2 diabetes mellitus (T2DM) is a potential risk factor for the development of COVID-19 and is associated with higher severity and mortality rates. T2DM patients are commonly treated with metformin monotherapy or metformin plus sitagliptin. In the present case-control, single-center cohort study, a total number of 112 T2DM patients suffering from COVID-19 and aged 44−62 years old were compared with 78 T2DM patients without COVID-19 and aged 42−56 years old. Both the patient group and the control group were allocated into four groups. Group A: T2DM patients with COVID-19 on metformin treatments plus standard therapy (n = 60); group B: T2DM patients with COVID-19 on metformin plus sitagliptin plus standard therapy (n = 52); group C: T2DM patients without COVID-19 on metformin treatments (n = 40); and group D: T2DM patients without COVID-19 on metformin plus sitagliptin (n = 38). The investigation duration was 2−3 weeks. Anthropometric measurements, serological and biochemical investigations, pulmonary radiological findings, and clinical outcomes were evaluated. Only 101 T2DM patients with COVID-19 continued the study, 71 (70.29%) with mild-moderate COVID-19 and 30 (29.7%) with severe COVID-19 were compared with 78 T2DM patients as a control. Inflammatory biomarkers (C reactive protein, ferritin, and procalcitonin), a lung injury biomarker (lactate dehydrogenase), and a coagulopathy biomarker (D-dimer) were elevated in severe COVID-19 patients compared with mild-moderate COVID-19 (p < 0.05) and T2DM patients (p < 0.05). However, metformin plus sitagliptin was more effective than metformin monotherapy in T2DM patients with COVID-19, as evidenced by the mitigation of oxidative stress, CT scan score, and clinical outcomes. The present study confirmed the protective effects of this combination against the development of COVID-19 severity, as most T2DM COVID-19 patients develop mild-moderate forms. Herein, the combination of metformin and sitagliptin may lead to more beneficial effects than metformin monotherapy.

Novel hit of DPP-4Is as promising antihyperglycemic agents with dual antioxidant/anti-inflammatory effects for type 2 diabetes with/without COVID-19

DPP-4Is are well recognized therapy for type 2 diabetes. In spite of sharing a common mode of action, the chemical diversity among members of DPP-4Is raised the question whether structural differences may result in distinguished activities. DPP-4Is were recently explored as drug repurposing means for treatment of SARS-CoV-2 due to the urgent need for small molecule drugs for controlling infections. The use of DPP-4Is was not correlated with adverse COVID-19-related consequences among patients with type 2 diabetes. Inspired by these reasons and the importance of pyrimidinone ring as DPP-4I with both antioxidant and anti-inflammatory activities, we succeeded to prepare some novel pyrimidinone and thio-pyrimidinone derivatives, which were then screened for their antidiabetic activity and DPP-4 inhibition. In addition, their anti-inflammatory effect on LPS-stimulated RAW 264.7 cells were evaluated. Furthermore, their antioxidant activities were also tested.

An update on the interaction between COVID-19, vaccines, and diabetic kidney disease

Up to now, coronavirus disease 2019 (COVID-19) is still affecting worldwide due to its highly infectious nature anrapid spread. Diabetic kidney disease (DKD) is an independent risk factor for severe COVID-19 outcomes, and they have a certain correlation in some aspects. Particularly, the activated renin–angiotensin–aldosterone system, chronic inflammation, endothelial dysfunction, and hypercoagulation state play an important role in the underlying mechanism linking COVID-19 to DKD. The dipeptidyl peptidase-4 inhibitor is considered a potential therapy for COVID-19 and has similarly shown organ protection in DKD. In addition, neuropilin-1 as an alternative pathway for angiotensin-converting enzyme 2 also contributes to severe acute respiratory syndrome coronavirus 2 entering the host cells, and its decreased expression can affect podocyte migration and adhesion. Here, we review the pathogenesis and current evidence of the interaction of DKD and COVID-19, as well as focus on elevated blood glucose following vaccination and its possible mechanism. Grasping the pathophysiology of DKD patients with COVID-19 is of great clinical significance for the formulation of therapeutic strategies.

Non-Insulin Novel Antidiabetic Drugs Mechanisms in the Pathogenesis of COVID-19

The present study aimed to analyse the published data and to realize an update about the use and pathogenesis of the novel antidiabetic drugs, respectively, dipeptidyl peptidase-4 inhibitors (DPP-4i), glucagon-like peptide-1 receptor agonists (GLP-1 Ra), and sodium-glucose co-transporter-2 inhibitors (SGLT-2i), in patients with type 2 diabetes mellitus (T2DM) and coronavirus disease (COVID-19). Literature research in the PubMed and Web of Science database was performed in order to identify relevant published clinical trials and meta-analyses that include information about the treatment with novel antidiabetic agents in patients with T2DM and COVID-19. A total of seven articles were included, and their primary and secondary outcomes were reported and analysed. DPP-4i has mixed results on mortality in T2DM patients with COVID-19 but with an overall slightly favourable or neutral effect, whereas GLP-1 Ra seems to have a rather beneficial impact, while SGLT-2i may be useful in acute illness. Even if there are limited data, they seem to have favourable efficacy and safety profiles. The available evidence is heterogenous and insufficient to evaluate if the benefits of non-insulin novel antidiabetic drugs in COVID-19 treatment are due to the improvement of glycaemic control or to their intrinsic anti-inflammatory effects but highlights their beneficial effects in the pathogenesis and evolution of the disease.

The dipeptidyl peptidase-4 inhibitor linagliptin ameliorates LPS-induced acute lung injury by maintenance of pulmonary microvascular barrier via activating the Epac1/AKT pathway

Pulmonary microvascular endothelial cells (PMVECs) barrier dysfunction is a main pathophysiological feature of sepsis-related acute lung injury (ALI). This study aimed to investigate whether the dipeptidyl peptidase (DPP)-4 inhibitor linagliptin could protect against LPS-induced PMVECs barrier disruption and its underlying molecular mechanisms. A classical ALI animal model and LPS-treated PMVECs were applied and all were treated with or without linagliptin. Cellular experiments demonstrated that linagliptin could mitigate LPS-induced PMVECs hyperpermeability and intercellular junction (VE-cadherin, β-catenin, and ZO-1) disruption in a dose-dependent manner. Correspondingly, it was observed that linagliptin pretreatment distinctly relieved LPS-induced lung injury, oxidative stress, and pulmonary edema in vivo. Furthermore, we found that the inhibition of oxidative stress by linagliptin may be achieved by reversing impaired mitochondrial function. Mechanistically, linagliptin administration promoted the activation of the Epac1 pathway and its downstream AKT pathway, while inhibition of the Epac1/Akt signaling pathway significantly alleviated the above-mentioned protective effect of linagliptin on the PMVECs barrier. Taken together, these data suggest that linagliptin can effectively reserve PMVECs barrier dysfunction and inhibit oxidative stress to protect against ALI via activating the Epac1/AKT signaling pathway, and thus may become a potential clinical therapeutic strategy for ALI.

Vesicles of yeast cell wall-sitagliptin to alleviate neuroinflammation in Alzheimer's disease

A cell-based drug delivery system based on yeast-cell wall loaded with sitagliptin, a drug with an anti-inflammatory effect, was developed to control neuroinflammation associated with Alzheimer's disease. The optimized nanoparticles had a spherical shape with a negative surface charge, and were shown to be less toxic than the carrier and sitagliptin. Moreover, the nanoparticles caused anti-inflammatory effects against tumor necrosis factor-alpha in mice model of neuroinflammation. The pharmacokinetics study showed the brain concentration of drug in the nanoparticles group was much higher than in the control group. To evaluate the effect of P-glycoprotein on brain entry of sitagliptin, the experiment was repeated with verapamil, as a P-glycoprotein inhibitor. Brain concentration of the nanoparticles group remained approximately unchanged, proving the "Trojan Horse" effect of the developed nanocarriers. The results are promising for using yeast-cell wall as a carrier for targeted delivery to immune cells for the management of inflammation.

The anti-inflammatory feature of glucagon-like peptide-1 and its based diabetes drugs—Therapeutic potential exploration in lung injury

Since 2005, GLP-1 receptor (GLP-1R) agonists (GLP-1RAs) have been developed as therapeutic agents for type 2 diabetes (T2D). GLP-1R is not only expressed in pancreatic islets but also other organs, especially the lung. However, controversy on extra-pancreatic GLP-1R expression still needs to be further resolved, utilizing different tools including the use of more reliable GLP-1R antibodies in immune-staining and co-immune-staining. Extra-pancreatic expression of GLP-1R has triggered extensive investigations on extra-pancreatic functions of GLP-1RAs, aiming to repurpose them into therapeutic agents for other disorders. Extensive studies have demonstrated promising anti-inflammatory features of GLP-1RAs. Whether those features are directly mediated by GLP-1R expressed in immune cells also remains controversial. Following a brief review on GLP-1 as an incretin hormone and the development of GLP-1RAs as therapeutic agents for T2D, we have summarized our current understanding of the anti-inflammatory features of GLP-1RAs and commented on the controversy on extra-pancreatic GLP-1R expression. The main part of this review is a literature discussion on GLP-1RA utilization in animal models with chronic airway diseases and acute lung injuries, including studies on the combined use of mesenchymal stem cell (MSC) based therapy. This is followed by a brief summary.

The Potential Role of Cyclopeptides from Pseudostellaria heterophylla, Linum usitatissimum and Drymaria diandra, and Peptides Derived from Heterophyllin B as Dipeptidyl Peptidase IV Inhibitors for the Treatment of Type 2 Diabetes: An In Silico Study

Dipeptidyl peptidase 4 (DPP4) inhibitors can treat type 2 diabetes by slowing GLP-1 degradation to increase insulin secretion. Studies have reported that Pseudostellaria heterophylla, Linum usita-tissimum (flaxseed), and Drymaria diandra, plants rich in Caryophyllaceae-type cyclopeptides and commonly used as herbal or dietary supplements, are effective in controlling blood sugar. The active site of DPP4 is in a cavity large enough to accommodate their cyclopeptides. Molecular modeling by AutoDock Vina reveals that certain cyclopeptides in these plants have the potential for DPP4 inhibition. In particular, “Heterophyllin B” from P. heterophylla, “Cyclolinopeptide C” from flaxseed, and “Diandrine C” from D. diandra, with binding affinities of −10.4, −10.0, and −10.7 kcal/mol, are promising. Docking suggests that DPP4 inhibition may be one of the reasons why these three plants are beneficial for lowering blood sugar. Because many protein hydrolysates have shown the effect of DPP4 inhibition, a series of peptides derived from Heterophyllin B precursor “IFGGLPPP” were included in the study. It was observed that IFWPPP (−10.5 kcal/mol), IFGGWPPP (−11.4 kcal/mol), and IFGWPPP (−12.0 kcal/mol) showed good binding affinity and interaction for DPP4. Various IFGGLPPP derivatives have the potential to serve as scaffolds for the design of novel DPP4 inhibitors.

Knockdown of DPP4 promotes the proliferation and the activation of the CREB/aromatase pathway in ovarian granulosa cells

Dipeptidyl peptidase 4 (DPP4) has been revealed to be upregulated in women suffering from polycystic ovary syndrome (PCOS), which is a common reproductive disorder. The present study was designed to investigate the effects of inhibition of DPP4 expression on the proliferation of ovarian granulosa cells as well as on the activation of the cAMP response element‑binding protein (CREB)/aromatase pathway. The expression levels of DPP4 in rat serum samples with or without PCOS and ovarian granulosa cells (KGN cells) were detected using reverse transcription‑quantitative PCR (RT‑qPCR) and western blot analyses. Cell viability and cell cycle progression were detected using the Cell Counting Kit‑8 assay and flow cytometric analysis, respectively. The 5‑ethynyl‑2'‑deoxyuridine assay was employed to detect the proliferation of glycolaldehyde‑bovine serum albumin (GOA‑BSA)‑treated KGN cells. In addition, RT‑qPCR and western blot analyses were applied to detect the expression levels of CREB, specific cell cycle‑associated proteins and cytochrome P450 (CYP) 19A1 and CYP11A1 enzymes in KGN cells. The expression levels of DPP4 were upregulated in rats with PCOS. Inhibition of DPP4 expression promoted the proliferation and cell cycle arrest of KGN cells. It was also revealed that the expression levels of cell cycle‑associated proteins were upregulated in DPP4‑silenced KGN cells. In addition, their proliferation was decreased following treatment with GOA‑BSA, while the addition of sitagliptin partially reversed these effects. Additionally, sitagliptin reversed the inhibitory effects caused by GOA‑BSA treatment on the cell cycle progression and on the activation of the CREB/aromatase pathway in KGN cells, as determined by the increased expression levels of the cell cycle‑associated proteins as well as those of the CREB protein and the CYP19A1 and CYP11A1 enzymes. In conclusion, inhibition of DPP4 expression promoted the proliferation of KGN cells and the activation of the CREB/aromatase pathway.

Effect of linagliptin plus insulin in comparison to insulin alone on metabolic control and prognosis in hospitalized patients with SARS-CoV-2 infection

To evaluate the effect of the combination of linagliptin and insulin on metabolic control and prognosis in hospitalized patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and hyperglycemia. A parallel double-blind randomized clinical trial including hospitalized patients with SARS-CoV-2 infection and hyperglycemia, randomized to receive 5 mg linagliptin + insulin (LI group) or insulin alone (I group) was performed. The main outcomes were the need for assisted mechanical ventilation and glucose levels during hospitalization. Subjects were screened for eligibility at hospital admission if they were not with assisted mechanical ventilation and presented hyperglycemia, and a total of 73 patients with SARS-CoV-2 infection and hyperglycemia were randomized to the LI group (n = 35) or I group (n = 38). The average hospital stay was 12 ± 1 vs 10 ± 1 days for the I and LI groups, respectively (p = 0.343). There were no baseline clinical differences between the study groups, but the percentage of males was higher in the LI group (26 vs 18, p = 0.030). The improvements in fasting and postprandial glucose levels were better in the LI group that the I group (122 ± 7 vs 149 ± 10, p = 0.033; and 137 ± 7 vs 173 ± 12, p = 0.017, respectively), and insulin requirements tended to be lower in the LI group than the I group. Three patients in the LI group and 12 in the I group required assisted mechanical ventilation (HR 0.258, CI 95% 0.092–0.719, p = 0.009); 2 patients in the LI group and 6 in the I group died after a follow-up of 30 days (p = 0.139). No major side effects were observed. The combination of linagliptin and insulin in hospitalized patients with SARS-CoV-2 infection and hyperglycemia reduced the relative risk of assisted mechanical ventilation by 74% and improved better pre and postprandial glucose levels with lower insulin requirements, and no higher risk of hypoglycemia.

This study is registered at clinicaltrials.gov, number NCT04542213 on 09/03/2020.

Sphingosine Kinase 1 Plays an Important Role in Atorvastatin-Mediated Anti-Inflammatory Effect against Acute Lung Injury

Atorvastatin is a 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) inhibitor and inhibits cholesterol synthesis. Recently, atorvastatin also showed anti-inflammatory effect in acute lung injury, ameliorating pulmonary gas-blood exchanging function. Sphingosine kinase 1 plays a central role in endothelial (EC) cytoskeleton rearrangement and EC barrier integrity regulation. In this study, the role of sphingosine kinase 1 in atorvastatin anti-inflammatory effect against acute lung injury was investigated. Both wild-type (WT) and SphK1^-/- mice were challenged with high tidal volume ventilation (40 ml/kg body weight, 65 breathing/min, 4 hours). The acute lung injury was evaluated and the mechanisms were explored. In WT mice, atorvastatin treatment significantly decreased acute lung injury responding to high tidal volume ventilation (HT), including protein, cellular infiltration, and cytokine releasing; comparing to WT mice, SphK1^-/- mice showed significantly worsen pulmonary injuries on HT model. Moreover, the atorvastatin-mediated anti-inflammatory effect was diminished in SphK1^-/- mice. To further confirm the role of SphK1 in VILI, we then compared the inflammatory response of endothelial cells that were isolated from WT and SphK1^-/- mice to cyclic stretching. Similarly, atorvastatin significantly decreased cytokine generation from WT EC responding to cyclic stretching. Atorvastatin also significantly preserved endothelial junction integrity in WT EC against thrombin challenge. However, the inhibitory effect of atorvastatin on cytokine generation induced by cyclic stretching was abolished on SphK1^-/- mice EC. The endothelial junction integrity effects of atorvastatin also diminished on SphK1^-/- mouse EC. Signal analysis indicated that atorvastatin inhibited JNK activation induced by cyclic stretch. SphK1 knockout also blocked atorvastatin-mediated VE-cadherin junction enhancement. In summary, by inhibition of MAPK activity and maintenance of EC junction homeostasis, SphK1 plays a critical role in atorvastatin-mediated anti-inflammatory effects in both cellular and in vivo model. This study also offers an insight into mechanical stress-mediated acute lung injury and potential therapy in the future.

SARS-CoV-2 cell entry beyond the ACE2 receptor

BACKGROUND

Angiotensin-converting enzyme 2 (ACE2) is known as the major viral entry site for SARS-CoV-2. However, viral tissue tropism and high rate of infectivity do not directly correspond with the level of ACE2 expression in the organs. It may suggest involvement of other receptors or accessory membrane proteins in SARSCoV-2 cell entry.

METHODS AND RESULTS

A systematic search was carried out in PubMed/Medline, EMBASE, and Cochrane Library for studies reporting SARS-CoV-2 cell entry. We used a group of the MeSH terms including "cell entry", "surface receptor", "ACE2", and "SARS-CoV-2". We reviewed all selected papers published in English up to end of February 2022. We found several receptors or auxiliary membrane proteins (including CD147, NRP-1, CD26, AGTR2, Band3, KREMEN1, ASGR1, ANP, TMEM30A, CLEC4G, and LDLRAD3) along with ACE2 that facilitate virus entry and transmission. Expression of Band3 protein on the surface of erythrocytes and evidence of binding with S protein of SARS-CoV-2 may explain asymptomatic hypoxemia during COVID19 infection. The variants of SARS-CoV-2 including the B.1.1.7 (Alpha), B.1.617.1 (Kappa), B.1.617.2 (Delta), B.1.617.2+ (Delta+), and B.1.1.529 (Omicron) may have different potency to bond with these receptors.

CONCLUSIONS

The high rate of infectivity of SARS-CoV-2 may be due to its ability to enter the host cell through a group of cell surface receptors. These receptors are potential targets to develop novel therapeutic agents for SARS-CoV-2.

Diabetes and COVID-19; A Bidirectional Interplay

There seems to be a bidirectional interplay between Diabetes mellitus (DM) and coronavirus disease 2019 (COVID-19). On the one hand, people with diabetes are at higher risk of fatal or critical care unit-treated COVID-19 as well as COVID-19 related health complications compared to individuals without diabetes. On the other hand, clinical data so far suggest that the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may result in metabolic dysregulation and in impaired glucose homeostasis. In addition, emerging data on new onset DM in previously infected with SARS-CoV-2 patients, reinforce the hypothesis of a direct effect of SARS-CoV-2 on glucose metabolism. Attempting to find the culprit, we currently know that the pancreas and the endothelium have been found to express Angiotensin-converting enzyme 2 (ACE2) receptors, the main binding site of the virus. To move from bench to bedside, understanding the effects of COVID-19 on metabolism and glucose homeostasis is crucial to prevent and manage complications related to COVID-19 and support recovering patients. In this article we review the potential underlying pathophysiological mechanisms between COVID-19 and glucose dysregulation as well as the effects of antidiabetic treatment in patients with diabetes and COVID-19.

The Roles of Dipeptidyl Peptidase 4 (DPP4) and DPP4 Inhibitors in Different Lung Diseases: New Evidence

CD26/Dipeptidyl peptidase 4 (DPP4) is a type II transmembrane glycoprotein that is widely expressed in various organs and cells. It can also exist in body fluids in a soluble form. DPP4 participates in various physiological and pathological processes by regulating energy metabolism, inflammation, and immune function. DPP4 inhibitors have been approved by the Food and Drug Administration (FDA) for the treatment of type 2 diabetes mellitus. More evidence has shown the role of DPP4 in the pathogenesis of lung diseases, since it is highly expressed in the lung parenchyma and the surface of the epithelium, vascular endothelium, and fibroblasts of human bronchi. It is a potential biomarker and therapeutic target for various lung diseases. During the coronavirus disease-19 (COVID-19) global pandemic, DPP4 was found to be an important marker that may play a significant role in disease progression. Some clinical trials on DPP4 inhibitors in COVID-19 are ongoing. DPP4 also affects other infectious respiratory diseases such as Middle East respiratory syndrome and non-infectious lung diseases such as pulmonary fibrosis, lung cancer, chronic obstructive pulmonary disease (COPD), and asthma. This review aims to summarize the roles of DPP4 and its inhibitors in infectious lung diseases and non-infectious diseases to provide new insights for clinical physicians.

The early start of hemoperfusion decreases the mortality rate among severe COVID-19 patients: A preliminary study

BACKGROUND

Coronavirus disease-2019 (COVID-19)-related organ failure is partly related to a sepsis-like syndrome and extreme pro-inflammatory cytokine release, named cytokine storm. Therapeutic strategies that prevent the production of or remove the pro-inflammatory cytokines could potentially be an effective therapy in critically afflicted COVID-19 patients.

METHODS

In this clinical trial study, from April until June 2020, 68 COVID-19 patients (35 vs. 33 controls) with severe critical symptoms, and PaO₂ /FiO₂ (P/F) ratio less than 200 mmHg either received a single standard therapy or a combination of standard treatment for COVID-19 combined with hemoperfusion (hemofilter, HA330 D Javfron) for 4 h, in 3 consecutive days. The length of hospital stay and mechanical ventilation, the resolution of radiologic abnormalities, and the mortality rate were defined as the primary outcomes.

RESULTS

Demographic characteristics, the acute physiology, and chronic health evaluation score of both groups were similar (p > 0.05). Importantly, we noticed a significant mortality rate reduction in the perfused group compared with controls (37.1% vs. 63.6%, p = 0.02), this positive effect was stronger among those with a P/F ratio higher than 75 (mortality rate of 84.7% for P/F ratio < 75 vs. 15.4% for P/F ratio ≥ 75, p = 0.02).

CONCLUSIONS

The results imply that early start of hemoperfusion could be more effective and significantly reduce the mortality rate among COVID-19 patients with critical diseases.

Functional Roles for CD26/DPP4 in Mediating Inflammatory Responses of Pulmonary Vascular Endothelial Cells

Excessive inflammation in the lung is a primary cause of acute respiratory distress syndrome (ARDS). CD26/dipeptidyl peptidase-4 (DPP4) is a transmembrane protein that is expressed in various cell types and exerts multiple pleiotropic effects. We recently reported that pharmacological CD26/DPP4 inhibition ameliorated lipopolysaccharide (LPS)-induced lung injury in mice and exerted anti-inflammatory effects on human lung microvascular endothelial cells (HLMVECs), in vitro. However, the mechanistic roles of CD26/DPP4 in lung injury and its effects on HLMVECs remain unclear. In this study, transcriptome analysis, followed by various confirmation experiments using siRNA in cultured HLMVECs, are performed to evaluate the role of CD26/DPP4 in response to the pro-inflammatory involved in inflammation, barrier function, and regenerative processes in HLMVECs after pro-inflammatory stimulation. These are all functions that are closely related to the pathophysiology and repair process of lung injury. Confirmatory experiments using flow cytometry; enzyme-linked immunosorbent assay; quantitative polymerase chain reaction; dextran permeability assay; WST-8 assay; wound healing assay; and tube formation assay, reveal that the reduction of CD26/DPP4 via siRNA is associated with altered parameters of inflammation, barrier function, and the regenerative processes in HLMVECs. Thus, CD26/DPP4 can play a pathological role in mediating injury in pulmonary endothelial cells. CD26/DPP4 inhibition can be a new therapeutic strategy for inflammatory lung diseases, involving pulmonary vascular damage.

Association between cardiometabolic risk factors and COVID-19 susceptibility, severity and mortality: a review

The novel coronavirus, which began spreading from China Wuhan and gradually spreaded to most countries, led to the announcement by the World Health Organization on March 11, 2020, as a new pandemic. The most important point presented by the World Health Organization about this disease is to better understand the risk factors that exacerbate the course of the disease and worsen its prognosis. Due to the high majority of cardio metabolic risk factors like obesity, hypertension, diabetes, and dyslipidemia among the population over 60 years old and higher, these cardio metabolic risk factors along with the age of these people could worsen the prognosis of the coronavirus disease of 2019 (COVID-19) and its mortality. In this study, we aimed to review the articles from the beginning of the pandemic on the impression of cardio metabolic risk factors on COVID-19 and the effectiveness of COVID-19 on how to manage these diseases. All the factors studied in this article, including hypertension, diabetes mellitus, dyslipidemia, and obesity exacerbate the course of Covid-19 disease by different mechanisms, and the inflammatory process caused by coronavirus can also create a vicious cycle in controlling these diseases for patients.

Correlation between circulating endothelial cell level and acute respiratory distress syndrome in postoperative patients

BACKGROUND

Acute respiratory distress syndrome (ARDS) is injury of alveolar epithelial cells and capillary endothelial cells caused by various factors, including endogenous and exogenous lung factors, leading to diffuse pulmonary interstitial and alveolar edema, and acute respiratory failure. ARDS involves alveolar epithelial cells and pulmonary interstitial capillary endothelial cells. Circulating endothelial cells (CECs) are the only marker that directly reflects vascular endothelial injury in vivo. There have been few studies on the correlation between peripheral blood CECs and ARDS at home and abroad. The lungs are the organs with the highest capillary density and the most endothelial cells, thus, it is speculated that when ARDS occurs, CECs are stimulated and damaged, and released into the circulatory system.

AIM

To explore the correlation between CEC level and severity of ARDS in patients postoperatively.

METHODS

Blood samples were collected from all patients on day 2 (d2) and day 5 (d5) after surgery. The control group comprised 32 healthy volunteers. Number of CECs was measured by flow cytometry, and operation time was recorded. Changes in various indexes of patients were monitored, and diagnosis of ARDS was determined based on ARDS Berlin definition. We comprised d2 CECs in different groups, correlation between operation time and d2 CECs, ARDS of different severity by d2 CECs, and predictive value of d2 CECs for ARDS in postoperative patients.

RESULTS

The number of d2 CECs in the ARDS group was significantly higher than that in the healthy control group (P < 0.001). The number of d2 CECs in the ARDS group was significantly higher than that in the non-ARDS group (P < 0.001). The number of d2 CECs in the non-ARDS group was significantly higher than that in the healthy control group (P < 0.001). Operation time was positively correlated with number of CECs on d2 (rs = 0.302, P = 0.001). The number of d2 CECs in the deceased group was significantly higher than that in the improved group (P < 0.001). There was no significant difference in number of d2 CECs between patients with mild and moderate ARDS. The number of d2 CECs in patients with severe ARDS was significantly higher than that in patients with mild and moderate ARDS (P = 0.041, P = 0.037). There was no significant difference in number of d5 and d2 CECs in the non-ARDS group after admission to intensive care. The number of d5 CECs was higher than the number of d2 CECs in the ARDS improved group (P < 0.001). The number of d5 CECs was higher than the number of d2 CECs in the ARDS deceased group (P = 0.002). If the number of CECs was > 1351/mL, sensitivity and specificity of predicting ARDS were 80.8% and 78.1%, respectively.

CONCLUSION

Changes in number of CECs might predict occurrence and adverse outcome of ARDS after surgery, and higher numbers of CECs indicate worse prognosis of ARDS.

Anagliptin alleviates lipopolysaccharide-induced inflammation, apoptosis and endothelial dysfunction of lung microvascular endothelial cells

It has been reported that dipeptidyl peptidase-4 (DPP4) inhibition protects against acute lung injury (ALI). Anagliptin is a novel selective inhibitor of DPP4 but its role in ALI has not been studied. The present study aimed to investigate the effects of anagliptin on lipopolysaccharide (LPS)-induced human pulmonary microvascular endothelial cell (HPMVEC) injury, as well as its underlying mechanism. HPMVECs were exposed to LPS in the presence or absence of anagliptin co-treatment. MTT assay was used to evaluate cell viability and nitric oxide (NO) production was detected using a commercial kit. DPP4 and pro-inflammatory cytokine expression levels, apoptosis and migration were assessed via reverse transcription-quantitative PCR, western blotting, TUNEL staining and wound healing assay, respectively. Western blot analysis was performed to assess expression levels of proteins involved in NF-κB signaling, cell apoptosis and migration, as well as high mobility group box 1 (HMGB1)/receptor for advanced glycation end products (RAGE). LPS decreased cell viability and NO production, but elevated expression of DPP4 in HPMVECs. LPS promoted pro-inflammatory cytokine expression, NF-κB activation and cell apoptosis, but inhibited cell migration and phosphorylated-AKT/endothelial NO synthase expression. Anagliptin co-treatment significantly restored all of these effects. Mechanistically, the upregulation of HMGB1/RAGE expression induced by LPS was markedly blocked by anagliptin. In conclusion, anagliptin alleviated inflammation, apoptosis and endothelial dysfunction in LPS-induced HPMVECs via modulating HMGB1/RAGE expression. These data provide a basis for use of anagliptin in ALI treatment.

Differential urine proteome analysis of a ventilator-induced lung injury rat model by label-free quantitative and parallel reaction monitoring proteomics

Urine is a promising resource for biomarker research. Therefore, the purpose of this study was to investigate potential urinary biomarkers to monitor the disease activity of ventilator-induced lung injury (VILI). In the discovery phase, a label-free data-dependent acquisition (DDA) quantitative proteomics method was used to profile the urinary proteomes of VILI rats. For further validation, the differential proteins were verified by parallel reaction monitoring (PRM)-targeted quantitative proteomics. In total, 727 high-confidence proteins were identified with at least 1 unique peptide (FDR ≤ 1%). Compared to the control group, 110 proteins (65 upregulated, 45 downregulated) were significantly changed in the VILI group (1.5-fold change, P < 0.05). The canonical pathways and protein-protein interaction analyses revealed that the differentially expressed proteins were enriched in multiple functions, including oxidative stress and inflammatory responses. Finally, thirteen proteins were identified as candidate biomarkers for VILI by PRM validation. Among these PRM-validated proteins, AMPN, MEP1B, LYSC1, DPP4 and CYC were previously reported as lung-associated disease biomarkers. SLC31, MEP1A, S15A2, NHRF1, XPP2, GGT1, HEXA, and ATPB were newly discovered in this study. Our results suggest that the urinary proteome might reflect the pathophysiological changes associated with VILI. These differential proteins are potential urinary biomarkers for the activity of VILI.

Managing diabetes in diabetic patients with COVID: where do we start from?

AIMS

COVID-19 has and still is sweeping away the national health systems worldwide. In this review, we sought to determine the evidence base proofs on the antidiabetic treatment capable to reduce the risk of COVID-19-related mortality.

METHODS

We have performed a systematic search of published articles using PubMed, and EMBASE from March 2020 to March 31st, 2021. We excluded editorials, commentary, letters to the editor, reviews, and studies that did not have mortality as an outcome. For metformin and insulin only, we performed a meta-analysis using Cochrane RevMan 5.2.

RESULTS

Among antidiabetic drugs, metformin was the only drug associated with a reduced risk of mortality. Conversely, insulin appears associated with an increased risk. The other classes of drugs were neutral.

CONCLUSIONS

The totality of articles reports retrospective data strongly affected by "channeling bias" so that most of the existing results on each class of drugs are driven by the phenotype of patients likely to receive that specific drug by prescription.

SARS-CoV-2 and diabetes: A potential therapeutic effect of dipeptidyl peptidase 4 inhibitors in diabetic patients diagnosed with COVID-19

COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 and has become an urgent economic and health challenge. Dipeptidyl peptidase 4 (DPP4), also mentioned as a cluster of differentiation 26 (CD26) is a serine exopeptidase found in two arrangements: a soluble form (sDPP-4) and a plasma membrane-bound form. Because other coronaviruses enter the cells by binding to DPP-4, it has been speculated that DPP-4 inhibitors may exert activity against COVID-19. Therefore, this review aimed to summarize the potential therapeutic effect of dipeptidyl peptidase 4 inhibitors in diabetic patients diagnosed with COVID-19. To include different studies, publications related to Dipeptidyl peptidase-4 inhibitor use and clinical outcomes from COVID-19 were searched from the databases such as Web of Science, PubMed, Medline, Elsevier, Google Scholar, and SCOPUS, via English key terms. A direct engrossment of DPP4 in COVID-19 needs to be elucidated, there is also evidence confirming that DPP4 inhibitors exert anti-fibrotic and modulate inflammation activity. Thus, the use of DPP-4 inhibitors could reduce mortality due to COVID-19 or improve the progression of COVID-19; this evidence may support the management of diabetic patients diagnosed with COVID-19; however more well-designed investigation is urgently required.

Sitagliptin activates the p62-Keap1-Nrf2 signalling pathway to alleviate oxidative stress and excessive autophagy in severe acute pancreatitis-related acute lung injury

Acute lung injury (ALI) is a complication of severe acute pancreatitis (SAP). Sitagliptin (SIT) is a DPP4 inhibitor that exerts anti-inflammatory and antioxidant effects; however, its mechanism of action in SAP-ALI remains unclear. In this study, we investigated the effects of SIT on SAP-ALI and the specific pathways involved in SAP-induced lung inflammation, including oxidative stress, autophagy, and p62-Kelch-like ECH-associated protein 1 (Keap1)-NF-E2-related factor 2 (Nrf2) signalling pathways. Nrf2 knockout (Nrf2-/-) and wild-type (WT) mice were pre-treated with SIT (100 mg/kg), followed by caerulein and lipopolysaccharide (LPS) administration to induce pancreatic and lung injury. BEAS-2B cells were transfected with siRNA-Nrf2 and treated with LPS, and the changes in inflammation, reactive oxygen species (ROS) levels, and autophagy were measured. SIT reduced histological damage, oedema, and myeloperoxidase activity in the lung, decreased the expression of pro-inflammatory cytokines, and inhibited excessive autophagy and ROS production via the activation of the p62-Keap1-Nrf2 signalling pathway and promotion of the nuclear translocation of Nrf2. In Nrf2-knockout mice, the anti-inflammatory effect of SIT was reduced, resulting in ROS accumulation and excessive autophagy. In BEAS-2B cells, LPS induced ROS production and activated autophagy, further enhanced by Nrf2 knockdown. This study demonstrates that SIT reduces SAP-ALI-associated oxidative stress and excessive autophagy through the p62-Keap1-Nrf2 signalling pathway and nuclear translocation of Nrf2, suggesting its therapeutic potential in SAP-ALI.

Lung development and immune status under chronic LPS exposure in rat pups with and without CD26/DPP4 deficiency

Dipeptidyl-peptidase IV (CD26), a multifactorial integral type II protein, is expressed in the lungs during development and is involved in inflammation processes. We tested whether daily LPS administration influences the CD26-dependent retardation in morphological lung development and induces alterations in the immune status. Newborn Fischer rats with and without CD26 deficiency were nebulized with 1 µg LPS/2 ml NaCl for 10 min from days postpartum (dpp) 3 to 9. We used stereological methods and fluorescence activated cell sorting (FACS) to determine morphological lung maturation and alterations in the pulmonary leukocyte content on dpp 7, 10, and 14. Daily LPS application did not change the lung volume but resulted in a significant retardation of alveolarization in both substrains proved by significantly lower values of septal surface and volume as well as higher mean free distances in airspaces. Looking at the immune status after LPS exposure compared to controls, a significantly higher percentage of B lymphocytes and decrease of CD4⁺CD25⁺ T cells were found in both subtypes, on dpp7 a significantly higher percentage of CD4 T⁺ cells in CD26⁺ pups, and a significantly higher percentage of monocytes in CD26⁻ pups. The percentage of T cells was significantly higher in the CD26-deficient group on each dpp. Thus, daily postnatal exposition to low doses of LPS for 1 week resulted in a delay in formation of secondary septa, which remained up to dpp 14 in CD26⁻ pups. The retardation was accompanied by moderate parenchymal inflammation and CD26-dependent changes in the pulmonary immune cell composition.

Factors influencing on development of COVID-19 pneumonia and association with oral anti-diabetic drugs in hospitalized patients with diabetes mellitus

BACKGROUND

Diabetes mellitus (DM) increases mortality and morbidity in patients with coronavirus disease (COVID-19). In this study, it was aimed to assess factors influencing on COVID-19 pneumonia in hospitalized patients with diabetes and association with oral anti-diabetic drugs.

MATERIALS AND METHODS

This cross-sectional study included 432 patients with type 2 diabetes mellitus diagnosed with COVID-19. Data regarding clinical characteristics, demographic characteristics, intensive care unit (ICU) rate in patients admitted to ICU, laboratory results on day 1 and 7, thoracic computed tomography (CT) findings and oral anti-diabetic drugs used were extracted from medical records. In all patients, 75-days mortality was recorded. Data were assessed independently.

RESULTS

There was pneumonia in 386 (89.4%) of 432 patients with diabetes. The risk for pneumonia was markedly higher in patients on DPP-4 inhibitors; however, there was no significant among other oral anti-diabetic groups and subgroups. In addition, elevated CRP was linked to the increased risk for pneumonia. Only patients in the pneumonia group had SGLT-2 inhibitor use. During follow-up, 91 patients died. In Cox regression analysis, low Glasgow Coma Scale score, and increased lactate dehydrogenase levels were identified as significant independent risk factors for mortality.

CONCLUSION

The study indicated that DPP-4 inhibitor used and elevated CRP level were associated with pneumonia development. Only patients in the pneumonia group had SGLT-2 inhibitor use. No oral anti-diabetics was found to be associated with COVID-19 related death.

Sitagliptin Reduces Endothelial Dysfunction and Apoptosis Induced by High-Fat Diet and Palmitate in Thoracic Aortas and Endothelial Cells via ROS-ER Stress-CHOP Pathway

Macrovascular disease is tightly associated with obesity-induced metabolic syndrome. Sitagliptin (SIT), an orally stable selective inhibitor of Dipeptidyl peptidase-4 (DPP-4), has protective effects on endothelium. However, the mechanisms enabling SIT to exhibit resistance to diet-induced obesity (DIO) related with reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress in the aorta and endothelial cells have not been reported yet. Therefore, the present study was conducted to determine if SIT exerts protective role in the thoracic aortas isolated from the high-fat diet (HFD)-treated rats and palmitate (PA)-treated endothelial cells by alleviating ROS and ER stress. Male Sprague Dawley rats were randomly divided into standard chow diet (SCD), HFD and HFD plus sitagliptin administration (HFD + SIT) groups. The rats of latter two groups were given HFD fodder for 12 weeks, then the HFD + SIT rats were treated with SIT (10 mg/kg/d) by intragastric administration for another 8 weeks. The body mass, vascular tension, serum oxidative stress indices and inflammatory parameters, pathological changes, protein expression of endothelial nitric oxide synthase (eNOS), the genes associated with ER stress and apoptosis in the thoracic aorta were measured. Furthermore, cell proliferation, ROS and the protein expression associated with ER stress (especially CHOP) and apoptosis were assessed in human umbilical vein endothelial cells (HUVECs) incubated with SIT and PA. Compared to the SCD rats, the HFD rats had higher serum lipid levels, decreased vascular tension, increased inflammation, oxidative and ER stress, and apoptosis of endothelial cells. PA promoted ROS generation, ER stress and apoptosis, inhibited cell proliferation in HUVECs. SIT treatment obviously ameliorated apoptosis via alleviating ROS and ER stress in the thoracic aortas isolated from HFD-fed rats and PA-treated HUVECs. The results suggest that SIT improved endothelial function via promoting cell proliferation and alleviating ROS-ER stress-CHOP pathway both in vivo and in vitro.

Contribution of dipeptidyl peptidase 4 to non-typeable Haemophilus influenzae-induced lung inflammation in COPD

Dipeptidyl peptidase 4 (DPP4) expression is increased in the lungs of chronic obstructive pulmonary disease (COPD). DPP4 is known to be associated with inflammation in various organs, including LPS-induced acute lung inflammation. Since non-typeable Haemophilus influenzae (NTHi) causes acute exacerbations in COPD patients, we examined the contribution of DPP4 in NTHi-induced lung inflammation in COPD. Pulmonary macrophages isolated from COPD patients showed higher expression of DPP4 than the macrophages isolated from normal subjects. In response to NTHi infection, COPD, but not normal macrophages show a further increase in the expression of DPP4. COPD macrophages also showed higher expression of IL-1β, and CCL3 responses to NTHi than normal, and treatment with DPP4 inhibitor, diprotin A attenuated this response. To examine the contribution of DPP4 in NTHi-induced lung inflammation, COPD mice were infected with NTHi, treated with diprotin A or PBS intraperitoneally, and examined for DPP4 expression, lung inflammation, and cytokine expression. Mice with COPD phenotype showed increased expression of DPP4, which increased further following NTHi infection. DPP4 expression was primarily observed in the infiltrated inflammatory cells. NTHi-infected COPD mice also showed sustained neutrophilic lung inflammation and expression of CCL3, and this was inhibited by DPP4 inhibitor. These observations indicate that enhanced expression of DPP4 in pulmonary macrophages may contribute to sustained lung inflammation in COPD following NTHi infection. Therefore, inhibition of DPP4 may reduce the severity of NTHi-induced lung inflammation in COPD.

Identification of significant alteration genes, pathways and TFs induced by LPS in ARDS via bioinformatical analysis

Background and aims

Acute respiratory distress syndrome (ARDS) or acute lung injury (ALI) is one of the most common acute thoracopathy with complicated pathogenesis in ICU. The study is to explore the differentially expressed genes (DEGs) in the lung tissue and underlying altering mechanisms in ARDS.

Methods

Gene expression profiles of GSE2411 and GSE130936 were available from GEO database, both of them included in GPL339. Then, an integrated analysis of these genes was performed, including gene ontology (GO) and KEGG pathway enrichment analysis in DAVID database, protein–protein interaction (PPI) network construction evaluated by the online database STRING, Transcription Factors (TFs) forecasting based on the Cytoscape plugin iRegulon, and their expression in varied organs in The Human Protein Atlas.

Results

A total of 39 differential expressed genes were screened from the two datasets, including 39 up-regulated genes and 0 down-regulated genes. The up-regulated genes were mainly enriched in the biological process, such as immune system process, innate immune response, inflammatory response, and also involved in some signal pathways, including cytokine–cytokine receptor interaction, Salmonella infection, Legionellosis, Chemokine, and Toll-like receptor signal pathway with an integrated analysis. GBP2, IFIT2 and IFIT3 were identified as hub genes in the lung by PPI network analysis with MCODE plug-in, as well as GO and KEGG re-enrichment. All of the three hub genes were regulated by the predictive common TFs, including STAT1, E2F1, IRF1, IRF2, and IRF9.

Conclusions

This study implied that hub gene GBP2, IFIT2 and IFIT3, which might be regulated by STAT1, E2F1, IRF1, IRF2, or IRF9, played significant roles in ARDS. They could be potential diagnostic or therapeutic targets for ARDS patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06578-7.

Anti-Diabetic Drugs GLP-1 Agonists and DPP-4 Inhibitors may Represent Potential Therapeutic Approaches for COVID-19

The fast spread of coronavirus 2019 (COVID-19) calls for immediate action to counter the associated significant loss of human life and deep economic impact. Certain patient populations like those with obesity and diabetes are at higher risk for acquiring severe COVID-19 disease and have a higher risk of COVID-19 associated mortality. In the absence of an effective and safe vaccine, the only immediate promising approach is to repurpose an existing approved drug. Several drugs have been proposed and tested as adjunctive therapy for COVID-19. Among these drugs are the glucagon-like peptide-1 (GLP-1) 2 agonists and the dipeptidylpeptidase-4 (DPP-4) inhibitors. Beyond their glucose-lowering effects, these drugs have several pleiotropic protective properties, which include cardioprotective effects, anti-inflammatory and immunomodulatory activities, antifibrotic effects, antithrombotic effects, and vascular endothelial protective properties. This narrative review discusses these protective properties and addresses their scientific plausibility for their potential use as adjunctive therapy for COVID-19 disease.

Dipeptidyl Peptidase-4 Inhibitors and COVID-19-Related Deaths among Patients with Type 2 Diabetes Mellitus: A Meta-Analysis of Observational Studies

The coronavirus disease 2019 (COVID-19) pandemic remains an unbeaten enemy. Unfortunately, no targeted treatment option is available. Patients with type 2 diabetes mellitus (T2DM) have increased odds for severe or fatal disease, as demonstrated in recent observational studies. There is an ongoing discussion regarding the impact of different antidiabetic drug classes on outcomes of interest among affected subjects. Dipeptidyl peptidase-4 (DPP-4) inhibitors have been placed at the epicenter, since the DPP-4 enzyme seems to be implicated in the disease pathogenesis. Herein we present an updated meta-analysis of observational studies addressing the risk of COVID-19 death among patients with T2DM on prior DPP-4 inhibitor treatment. We pooled data from 10 observational studies, showing that DPP-4 inhibitors produce a non-significant decrease in the risk for COVID-19-related death. However, when administered in the inpatient setting, DPP-4 inhibitors decrease the risk for COVID-19-related death by 50%. Ongoing randomized controlled trials will shed further light.

Trelagliptin Alleviates Lipopolysaccharide (LPS)-Induced Inflammation and Oxidative Stress in Acute Lung Injury Mice

Acute lung injury (ALI) is an urgent disease lacking effective therapies, resulting in relatively high morbidity and mortality. The pathological mechanism of ALI is reported to be related to excessive inflammation and activated oxidative stress. The present study aims to investigate the protective effects of the DPP-4 inhibitor Trelagliptin against lipopolysaccharide (LPS)-induced ALI and the underlying mechanism. LPS was used to induce ALI mice models. The pathological condition of ALI mice was evaluated using MPO activity assay, lung wet to dry weight ratio detection, and HE staining on the lung tissues. Lung function was assessed using a spirometer. The oxidative stress level in the lung tissues was checked by MDA measurement and GPx detection using commercial kits. The leukocyte and neutrophil numbers were determined using a hemocytometer and the total concentration of protein in the BALF was detected using a bicinchoninic acid method. The expression levels of TNF-α, IL-6, and CXCL2 in the lung tissues were evaluated using qRT-PCR and ELISA. Western blot analysis was used to determine the expression levels of TLR4 and p-NF-κB p65. LPS-induced elevated MPO activity, pulmonary wet to dry weight ratio, airway resistance (RAW), the total number of leukocytes and neutrophils, production of inflammatory factors, decreased pulmonary dynamic compliance (Cdyn), and peak expiratory flow (PEF), and an aggravated histopathological state (such as disordered alveolar structure, significant pulmonary interstitial edema, and large numbers of red blood cells and inflammatory cells in the alveolar cavity) were significantly reversed by the administration of Trelagliptin. The TLR4/NF-κB signaling pathway was activated and oxidative stress was induced by stimulation with LPS; however, both effects were suppressed by the administration of Trelagliptin. Trelagliptin might alleviate LPS-induced inflammation and oxidative stress in acute lung injury mice.

Group V Phospholipase A2 Mediates Endothelial Dysfunction and Acute Lung Injury Caused by Methicillin-Resistant Staphylococcus Aureus

Lung endothelial dysfunction is a key feature of acute lung injury (ALI) and clinical acute respiratory distress syndrome (ARDS). Previous studies have identified the lipid-generating enzyme, group V phospholipase A2 (gVPLA2), as a mediator of lung endothelial barrier disruption and inflammation. The current study aimed to determine the role of gVPLA2 in mediating lung endothelial responses to methicillin-resistant Staphylococcus aureus (MRSA, USA300 strain), a major cause of ALI/ARDS. In vitro studies assessed the effects of gVPLA2 inhibition on lung endothelial cell (EC) permeability after exposure to heat-killed (HK) MRSA. In vivo studies assessed the effects of intratracheal live or HK-MRSA on multiple indices of ALI in wild-type (WT) and gVPLA2-deficient (KO) mice. In vitro, HK-MRSA increased gVPLA2 expression and permeability in human lung EC. Inhibition of gVPLA2 with either the PLA2 inhibitor, LY311727, or with a specific monoclonal antibody, attenuated the barrier disruption caused by HK-MRSA. LY311727 also reduced HK-MRSA-induced permeability in mouse lung EC isolated from WT but not gVPLA2-KO mice. In vivo, live MRSA caused significantly less ALI in gVPLA2 KO mice compared to WT, findings confirmed by intravital microscopy assessment in HK-MRSA-treated mice. After targeted delivery of gVPLA2 plasmid to lung endothelium using ACE antibody-conjugated liposomes, MRSA-induced ALI was significantly increased in gVPLA2-KO mice, indicating that lung endothelial expression of gVPLA2 is critical in vivo. In summary, these results demonstrate an important role for gVPLA2 in mediating MRSA-induced lung EC permeability and ALI. Thus, gVPLA2 may represent a novel therapeutic target in ALI/ARDS caused by bacterial infection.

Disentangling conflicting evidence on DPP-4 inhibitors and outcomes of COVID-19: narrative review and meta-analysis

BACKGROUND

The infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly spread all over the world, becoming pandemic. Several studies have shown that diabetes mellitus (DM) is an independent risk factor that increases mortality and other adverse outcomes of coronavirus disease-19 (COVID-19). Studies have suggested that SARS-CoV-2 may bind dipeptidyl peptidase-4 (DPP4) for entering cells of the respiratory tract. Besides, DPP4 takes part in immune system regulation. Thus, DPP-4 inhibitors (DPP4i) may play a role against COVID-19.

METHODS

We focused on the impact of DPP4i treatment on COVID-19-related outcomes in people with DM. For this purpose, we conducted a systematic review and meta-analysis to summarize the existing evidence on this topic.

RESULTS

Retrospective observational studies provide inconsistent results on the association between use of DPP4i and outcomes of COVID-19. While two studies reported significantly lower mortality rates among patients with DM who received DPP4i versus those who did not, a series of other studies showed no effect of DPP4i or even worse outcomes. A meta-analysis of 7 studies yielded a neutral estimate of the risk ratio of COVID-19-related mortality among users of DPP4i (0.81; 95% CI 0.57-1.15).

CONCLUSION

In the absence of randomized controlled trials, observational research available so far provides inconclusive results and insufficient evidence to recommend use of DPP4i against COVID-19.

Treatment with a DPP-4 inhibitor at time of hospital admission for COVID-19 is not associated with improved clinical outcomes: data from the COVID-PREDICT cohort study in The Netherlands

Purpose

Inhibition of dipeptidyl peptidase (DPP-)4 could reduce coronavirus disease 2019 (COVID-19) severity by reducing inflammation and enhancing tissue repair beyond glucose lowering. We aimed to assess this in a prospective cohort study.

Methods

We studied in 565 patients with type 2 diabetes in the CovidPredict Clinical Course Cohort whether use of a DPP-4 inhibitor prior to hospital admission due to COVID-19 was associated with improved clinical outcomes. Using crude analyses and propensity score matching (on age, sex and BMI), 28 patients using a DPP-4 inhibitor were identified and compared to non-users.

Results

No differences were found in the primary outcome mortality (matched-analysis = odds-ratio: 0,94 [95% confidence interval: 0,69 – 1,28], p-value: 0,689) or any of the secondary outcomes (ICU admission, invasive ventilation, thrombotic events or infectious complications). Additional analyses comparing users of DPP-4 inhibitors with subgroups of non-users (subgroup 1: users of metformin and sulphonylurea; subgroup 2: users of any insulin combination), allowing to correct for diabetes severity, did not yield different results.

Conclusions

We conclude that outpatient use of a DPP-4 inhibitor does not affect the clinical outcomes of patients with type 2 diabetes who are hospitalized because of COVID-19 infection.

DPP-4 inhibitors may improve the mortality of coronavirus disease 2019: A meta-analysis

Aims

DPP-4 inhibitors are predicted to exert a protective effect on the progression of coronavirus disease 2019 (COVID-19). We conducted this meta-analysis to investigate this hypothesis.

Methods

Four databases, namely, PubMed, Web of Science, EMBASE and the Cochrane Library, were used to identify studies on DPP-4 and COVID-19. The outcome indicators were the mortality of COVID-19. Funnel plots, Begg’s tests and Egger’s tests were used to assess publication bias.

Results

Four articles were included with a total of 1933 patients with COVID-19 and type 2 diabetes. The use of DPP-4 inhibitors was negatively associated with the risk of mortality (odds ratio (OR) = 0.58 95% confidence interval (CI), 0.34–0.99).

Conclusions

DPP-4 inhibitors may improve the mortality of patients with COVID-19 and type 2 diabetes. As few relevant studies are available, more large-scale studies need to be performed.