Nicotinamide adenine dinucleotide phosphate oxidase in pancreatic diseases: Mechanisms and future perspectives

Pancreatitis and pancreatic cancer (PC) stand as the most worrisome ailments affecting the pancreas. Researchers have dedicated efforts to unraveling the mechanisms underlying these diseases, yet their true nature continues to elude their grasp. Within this realm, oxidative stress is often believed to play a causal and contributory role in the development of pancreatitis and PC. Excessive accumulation of reactive oxygen species (ROS) can cause oxidative stress, and the key enzyme responsible for inducing ROS production in cells is nicotinamide adenine dinucleotide phosphate hydrogen oxides (NOX). NOX contribute to pancreatic fibrosis and inflammation by generating ROS that injure acinar cells, activate pancreatic stellate cells, and mediate macrophage polarization. Excessive ROS production occurs during malignant transformation and pancreatic carcinogenesis, creating an oxidative microenvironment that can cause abnormal apoptosis, epithelial to mesenchymal transition and genomic instability. Therefore, understanding the role of NOX in pancreatic diseases contributes to a more in-depth exploration of the exact pathogenesis of these diseases. In this review, we aim to summarize the potential roles of NOX and its mechanism in pancreatic disorders, aiming to provide novel insights into understanding the mechanisms underlying these diseases.

Protocol for isolation and spectral flow cytometry analysis of immune cells from the murine exocrine and endocrine pancreas

Diabetes mellitus is a disease of the hormone-secreting endocrine pancreas. However, increasing evidence suggests that the exocrine pancreas is also involved in the pathogenesis of diabetes. In this protocol, we describe how to harvest both isolated islets and exocrine tissue from one mouse pancreas, followed by a detailed explanation of how to isolate and analyze immune cells using full-spectrum flow cytometry.

Biomimetic Nanoparticles Loaded with Ulinastatin for the Targeted Treatment of Acute Pancreatitis

Ulinastatin is commonly used in the clinic to treat acute pancreatitis (AP), but its therapeutic effect was limited by the presence of the blood-pancreas barrier (BPB) and low specificity. Here, we prepared a macrophage biomimetic nanoparticle (MU) that delivered ulinastatin to address the above issues. Macrophage membrane was used as a shell for a mixture of PEG-PLGA and ulinastatin. It was found that MU showed good stability and biocompatibility in vitro and in vivo. According to in vivo fluorescence imaging, MU displayed a great inflammation targeting effect both in a subcutaneous inflammation model and in situ pancreatitis mouse model, which was ascribed to the presence of adhesion proteins. In vitro and in vivo results demonstrated that MU have a superior AP treatment effect by inhibiting pro-inflammatory factors and keeping cells viability. It was suggested the MU could provide a new strategy for targeted AP treatment.

Distinct Serum Immune Profiles Define the Spectrum of Acute and Chronic Pancreatitis From the Multicenter Prospective Evaluation of Chronic Pancreatitis for Epidemiologic and Translational Studies (PROCEED) Study

BACKGROUND & AIMS

Pancreatitis is a disease continuum, starting with acute pancreatitis (AP) and progressing in some cases to recurrent acute pancreatitis (RAP) and chronic pancreatitis (CP). Currently, there are no approved therapies or early diagnostic or prognostic biomarkers for pancreatitis. The current study examined whether patient serum immune profiling could identify noninvasive biomarkers and provide mechanistic insight into the disease continuum of pancreatitis.

METHODS

Using Olink immunoassay, we assessed the protein levels of 92 immune markers in serum samples from participants enrolled in the Prospective Evaluation of Chronic Pancreatitis for Epidemiologic and Translational Studies (PROCEED) study of the Chronic Pancreatitis, Diabetes, and Pancreatic Cancer (CPDPC) consortium. Samples (N = 231) were obtained from individuals without pancreatic disease (n = 56) and from those with chronic abdominal pain (CAP) (n = 24), AP (n = 38), RAP (n = 56), and CP (n = 57).

RESULTS

A total of 33 immune markers differentiated the combined pancreatitis groups from controls. Immune markers related to interleukin (IL) 17 signaling distinguished CP from AP and RAP. Similarly, the serum level of IL17A and C-C motif chemokine ligand 20 differentiated CP from CAP, suggesting the involvement of T helper 17 cells in CP pathogenesis. The receiver operator characteristic curve with 2 immune markers (IL17A and sulfotransferase 1A1) could differentiate CP from CAP (optimistic area under the curve = 0.78). The macrophage classical activation pathway elevated along the continuum of pancreatitis, suggesting an accumulation of proinflammatory signals over disease progression. Several immune markers were associated with smoking, alcohol, and diabetes status.

CONCLUSIONS

Immune profiling of serum samples from a large pancreatitis cohort led to identifying distinct immune markers that could serve as potential biomarkers to differentiate the varying pancreatitis disease states. In addition, the finding of IL17 signaling in CP could provide insight into the immune mechanisms underlying disease progression.

Multivalent mannose-conjugated siRNA causes robust gene silencing in pancreatic macrophages in vivo

Nucleic acid therapeutics have been utilized for gene regulation, and their recent advancement has led to approval of novel drugs for liver-related disorders. However, systemic extrahepatic delivery remains challenging. Here, we report newly designed mannose-conjugated oligonucleotides for delivering oligonucleotides to macrophages by leveraging the mannose receptor, C-type 1 (MRC1, CD206), which is abundantly expressed in macrophages. We investigated the relationship between cellular uptake and multivalency (mono to tetra) of mannose ligands or linker length and selected a trivalent-mannose ligand. Trivalent-mannose (Man3)-conjugated siRNA induced concentration-dependent gene silencing in both human CD206-overexpressing cells and human macrophages in vitro. After subcutaneous injection into mice, we observed a high distribution of Man3-conjugated oligonucleotides in the liver and pancreata as well as cellular uptake into Kupffer cells and pancreatic macrophages. A single subcutaneous injection of Man3-conjugated siRNA (10 mg/kg) targeting β₂-microglobulin (B2M) silenced B2m mRNA expression by ∼50% and decreased its protein levels in mouse pancreatic macrophages compared to those in saline-treated mice. Of note, multiple subcutaneous injections decreased B2m gene expression and B2M protein levels by ∼80% and ∼85%, respectively. These results show that mannose-conjugation with oligonucleotides is expected to help deliver oligonucleotides to macrophages and regulate gene expression in vivo, particularly in the pancreas.

Circulating monocytes in acute pancreatitis

Acute pancreatitis is a common gastrointestinal disease characterized by inflammation of the exocrine pancreas and manifesting itself through acute onset of abdominal pain. It is frequently associated with organ failure, pancreatic necrosis, and death. Mounting evidence describes monocytes - phagocytic, antigen presenting, and regulatory cells of the innate immune system - as key contributors and regulators of the inflammatory response and subsequent organ failure in acute pancreatitis. This review highlights the recent advances of dynamic change of numbers, phenotypes, and functions of circulating monocytes as well as their underling regulatory mechanisms with a special focus on the role of lipid modulation during acute pancreatitis.

Modulatory Role of Carbon Monoxide on the Inflammatory Response and Oxidative Stress Linked to Gastrointestinal Disorders

Significance: Carbon monoxide (CO) is an endogenous gaseous mediator that plays an important role in maintaining gastrointestinal (GI) tract homeostasis, acting in mucosal defense, and providing negative modulation of pathophysiological markers of clinical conditions. Recent Advances: Preclinical studies using animal models and/or cell culture show that CO can modulate the inflammatory response and oxidative stress in GI mucosal injuries and pathological conditions, reducing proinflammatory cytokines and reactive oxygen species, while increasing antioxidant defense mechanisms. Critical Issues: CO has potent anti-inflammatory and antioxidant effects. The defense mechanisms of the GI tract are subject to aggression by different chemical agents (e.g., drugs and ethanol) as well as complex and multifactorial diseases, with inflammation and oxidative stress as strong triggers for the deleterious effects. Thus, it is possible that CO acts on a variety of molecules involved in the inflammatory and oxidative signaling cascades, as well as reinforcing several defense mechanisms that maintain GI homeostasis. Future Directions: CO-based therapies are promising tools for the treatment of GI disorders, such as gastric and intestinal injuries, inflammatory bowel disease, and pancreatitis. Therefore, it is necessary to develop safe and selective CO-releasing agents and/or donor drugs to facilitate effective treatments and methods for analysis of CO levels that are simple and inexpensive. Antioxid. Redox Signal. 37, 98-114.

Disruption of monocyte-macrophage differentiation and trafficking by a heme analog during active inflammation

Heme metabolism is a key regulator of inflammatory responses. Cobalt protoporphyrin IX (CoPP) is a heme analog and mimic that potently activates the NRF2/heme oxygenase-1 (HO-1) pathway, especially in monocytes and macrophages. We investigated the influence of CoPP on inflammatory responses using a murine model of colitis. Surprisingly, conditional deletion of myeloid HO-1 did not impact the colonic inflammatory response or the protective influence of CoPP in the setting of dextran sodium sulfate-induced colitis. Rather, we reveal that CoPP elicits a contradictory shift in blood myeloid populations relative to the colon during active intestinal inflammation. Major population changes include markedly diminished trafficking of CCR2⁺Ly6C^hi monocytes to the inflamed colon, despite significant mobilization of this population into circulation. This resulted in significantly diminished colonic expansion of monocyte-derived macrophages and inflammatory cytokine expression. These findings were linked with significant induction of systemic CCL2 leading to a disrupted CCL2 chemoattractant gradient toward the colon and concentration-dependent suppression of circulating monocyte CCR2 expression. Administration of CoPP also induced macrophage differentiation toward a Marco^hiHmox1^hi anti-inflammatory erythrophagocytic phenotype, contributing to an overall decreased inflammatory profile. Such findings redefine protective influences of heme metabolism during inflammation, and highlight previously unreported immunosuppressive mechanisms of endogenous CCL2 induction.

CaMK II Inhibition Attenuates ROS Dependent Necroptosis in Acinar Cells and Protects against Acute Pancreatitis in Mice

As a calcium-regulated protein, CaMK II is closely related to cell death, and it participates in the development of pathological processes such as reperfusion injury, myocardial infarction, and oligodendrocyte death. The function of CaMK II activation in acute pancreatitis (AP) remains unclear. In our study, we confirmed that the expression of p-CaMK II was increased significantly and consistently in injured pancreatic tissues after caerulein-induced AP. Then, we found that KN93, an inhibitor of CaMK II, could mitigate the histopathological manifestations in pancreatic tissues, reduce serum levels of enzymology, and decrease oxidative stress products. Accordingly, we elucidated the effect of KN93 in vitro and found that KN93 had a protective effect on the pancreatic acinar cell necroptosis pathway by inhibiting the production of ROS and decreasing the expression of RIP3 and p-MLKL. In addition, we identified the protective effect of KN93 on AP through another mouse model induced by pancreatic duct ligation (PDL). Together, these data demonstrated that CaMK II participates in the development of AP and that inhibiting CaMK II activation could protect against AP by reducing acinar cell necroptosis, which may provide a new idea target for the prevention and treatment of AP in the clinic.

CD47 blockade enhances the efficacy of intratumoral STING-targeting therapy by activating phagocytes

Activation of STING signaling plays an important role in anti-tumor immunity, and we previously reported the anti-tumor effects of STING through accumulation of M1-like macrophages in tumor tissue treated with a STING agonist. However, myeloid cells express SIRPα, an inhibitory receptor for phagocytosis, and its receptor, CD47, is overexpressed in various cancer types. Based on our findings that breast cancer patients with highly expressed CD47 have poor survival, we evaluated the therapeutic efficacy and underlying mechanisms of combination therapy with the STING ligand cGAMP and an antagonistic anti-CD47 mAb using E0771 mouse breast cancer cells. Anti-CD47 mAb monotherapy did not suppress tumor growth in our setting, whereas cGAMP and anti-CD47 mAb combination therapy inhibited tumor growth. The combination therapy enhanced phagocytosis of tumor cells and induced systemic anti-tumor immune responses, which rely on STING and type I IFN signaling. Taken together, our findings indicate that coadministration of cGAMP and an antagonistic anti-CD47 mAb may be promising for effective cancer immunotherapy.

CORM-2 inhibits intracerebral hemorrhage-mediated inflammation

Background and purpose: Low-dose of carbon monoxide delivered by CO-releasing molecule-2 (CORM-2) had been confirmed having anti-inflammatory efficacy in some inflammatory diseases. Herein, we assessed the usefulness of CORM-2 in correcting intracerebral hemorrhage (ICH)-mediated inflammation.Methods: Healthy male Sprague Dawley (SD) rats randomly entered into four groups: sham-ICH, ICH, ICH+CORM-2, and ICH+ inactive carbon monoxide releasing molecule 2 (iCORM-2). ICH was induced by 50 μl of autologous arterial blood injected in situ in the rat brain. Neuro-functions of the ICH rats were evaluated with Garcia 18 scores at the 6th, 24th , 48th hou, and the fifthh day post-ICH. And brain tissues surrounding the hematoma area were collected from all ICH rats and assayed with Western blot and immunofluoresence analysis.Results: Neuro-dysfunctions in ICH rats were very severe than those in ICH +CORM-2 rats. Compared to sham group, the levels of HO-1, IKKβ, NF-κB, and TNF-α in ICH group began to elevate at the 6th hour, and reached to peak at the 48th hour post-ICH, all p < 0.05. While in ICH +CORM-2 group, the expressions of IKKβ, NF-κB, and TNF-α were very weaker than that in ICH group at every time points mentioned above; however, this phenomenon was not reproduced in ICH + iCORM-2 group. HO-1 in ICH+CORM-2 group highlighted in perihematomal area with many activated microglia (Iba-1-positive cells) and co-expressed with TNF-α, all of which were diminished at the fifth day post-ICH.Conclusion: CORM-2 may attenuate ICH-mediated inflammation by inhibiting microglial activation, which may involve the IKK/NF-κB pathway.AbbreviationsICH: intracerebral hemorrhage; CO: carbon monoxide; CORM-2: carbon monoxide releasing molecule-2; iCORM-2: inactive carbon monoxide releasing molecule-2; HO-1: heme oxygenase 1; IKKβ: inhibitor of IκB kinases β; NF-κB: nuclear factor-κB; TNF-α: tumor necrosis factor-α; Iba-1: ionized calcium binding adaptor molecule-1; IκB: inhibitor of NF-κB; iNOS: inducible nitric oxide synthase; Keap1: Kelch-like ECH-associated protein 1; Nrf2: NF-E2-related factor 2; DMSO: dimethylsulfoxide.

Electroacupuncture Ameliorates Acute Pancreatitis: A Role for the Vagus Nerve-Mediated Cholinergic Anti-Inflammatory Pathway

Organ failure resulting from excessive inflammation is the leading cause of death in the early phase of acute pancreatitis (AP). The autonomic nervous system was reported to be involved in AP, and the vagus nerve could exert anti-inflammatory effects through α7 nicotinic acetylcholine receptor (α7nAChR) signaling. Acupuncture has been widely used in traditional Asian medicine, and recent studies suggested the inflammation modulating effect of electroacupuncture (EA) might be mediated by the autonomic nervous system. In this study, we aimed to investigate the effects of EA in AP animal models. Two independent AP mouse models were used, namely, caerulein hyperstimulation and pancreatic duct ligation. We found that EA at Zusanli acupoint increased vagus nerve activity, suppressed systemic inflammation, and alleviated the histopathological manifestations and leukocyte infiltrations of the pancreas. Induction of AP resulted in a remarkable decrease in the frequency of α7nAchR⁺ macrophages in the pancreas, while EA counteracted this phenomenon. The anti-inflammatory, pancreatic protective and upregulation of α7nAchR effects of EA were reduced in mice with vagotomy. Moreover, the therapeutic effects of EA were attenuated in mice treated with methyllycaconitine citrate, a selective α7nAChR antagonist. Taken together, EA could modulate inflammation, thereby exerting protective effects in AP. The mechanism may include activating the vagus nerve through the cholinergic anti-inflammatory pathway.

Protectin D1 decreases pancreatitis severity in mice by inhibiting neutrophil extracellular trap formation

BACKGROUND

Docosahexaenoic acid-derived protectin D1 (PD1) was identified critical in the resolution of inflammation in vivo, where it modulates the innate immune response and stimulates resolution. Acute pancreatitis (AP) is characterized by local pancreatic inflammation with mild forms whereas systemic inflammation with severe forms. Herein we investigate the impact of PD1 in murine models of pancreatitis.

METHODS

Three independent AP models, which induced in male mice via intraperitoneal injection of caerulein, L-arginine or pancreatic duct ligation, were used to confirm the protective effect of PD1. Infiltrationsof neutrophils and macrophages in pancreas were detected by flow cytometry and immunohistochemistry. In vitro and in vivo neutrophil extracellular traps formation was detected by immunofluorescence staining. Expression of peptidylarginine deiminase 4 (PAD4) in activated neutrophils was evaluated by western blotting.

RESULTS

Systemic treatment with PD1 reduced serum activities of amylase and lipase, blunted the concentrations of tumor necrosis factor-α and interleukin-6 in serum and protected against pancreas histologic damage in three AP models. PD1 also prolonged the survival in the pancreatic duct ligation model. Moreover, pancreatic infiltrationofneutrophils and neutrophil CitH3 expression were reduced after PD1 administration. In vitro studies revealed PD1 decreased supernatant cell-free DNA and CitH3 levels and downregulated PAD4 expression in mouse bone-marrow derived neutrophils. However, in the caerulein mice pretreated with GSK484 hydrochloride, an inhibitor of PAD4, PD1 treatment showed no more protective effect.

CONCLUSIONS

PD1 ameliorates AP by decreasing early infiltration of neutrophils into the pancreas and neutrophil extracellular traps formation through PAD4. These results supply the foundation to consider PD1 as a therapy for AP.

The Proresolving Lipid Mediator Maresin1 Alleviates Experimental Pancreatitis via Switching Macrophage Polarization

Method

Repeated caerulein injection was used to induce AP and chronic pancreatitis (CP) models in mice. The histopathological and serological changes were examined for evaluating the severity of the AP model, and flow cytometry was used for detecting macrophage phagocytosis and phenotype. Meanwhile, clodronate liposomes were used for macrophage depletion in mice. Finally, the CP model was adopted to further observe the protective effect of MaR1.

Result

MaR1 administration manifested the improved histopathological changes and the lower serum levels of amylase and lipase. However, MaR1 played no protective role in the pancreatic acinar cell line in vitro. It obviously reduced the macrophage infiltration in the injured pancreas, especially M1-type macrophages. After macrophage clearance, MaR1 showed no further protection in vivo. This study also demonstrated that MaR1 could alleviate fibrosis to limit AP progression in the CP model.

Conclusion

Our data suggests that MaR1 was a therapeutic and preventive target for AP in mice, likely operating through its effects on decreased macrophage infiltration and phenotype switch.

Vagus Nerve Stimulation Decreases Pancreatitis Severity in Mice

Background

Vagus nerve stimulation (VNS) is effective in reducing inflammation in various diseases, such as rheumatoid arthritis, colitis and acute kidney injury. The anti-inflammatory effect of vagus nerve in these diseases necessitates the interactions of neural activation and α7 nicotinic acetylcholine receptors (α7nAChRs) on splenic macrophages. In this study, we aimed to investigate the effect of VNS on severity in experimental acute pancreatitis (AP).

Methods

Two independent AP models were used, which induced in ICR mice with caerulein or pancreatic duct ligation (PDL). Thirty minutes after modeling, the left cervical carotid sheath containing the vagus nerve was electrically stimulated for 2 min. Plasma lipase and amylase activities, TNF-α levels and pancreas histologic damage were evaluated. In caerulein mice, the percentages of α7nAChR⁺ macrophage in pancreas and spleen were assessed by flow cytometry. Furthermore, splenectomy and adoptive transfer of VNS-conditioned α7nAChR splenocytes were performed in caerulein mice to evaluate the role of spleen in the protective effect of VNS.

Results

VNS reduced plasma lipase and amylase activities, blunted the concentrations of TNF-α and protected against pancreas histologic damage in two AP models. Survival rates were improved in the PDL model after VNS. In caerulein AP mice, VNS increased the percentages of α7nAChR⁺ macrophages in pancreas and spleen. Adoptive transfer of VNS-treated α7nAChR splenocytes provided protection against pancreatitis in recipient mice. However, splenectomy did not abolish the protective effect of VNS.

Conclusions

VNS reduces disease severity and attenuates inflammation in AP mice. This effect is independent of spleen and is probably related to α7nAChR on macrophage.

Heme Oxygenase-1 in Gastrointestinal Tract Health and Disease

Heme oxygenase 1 (HO-1) is the rate-limiting enzyme of heme oxidative degradation, generating carbon monoxide (CO), free iron, and biliverdin. HO-1, a stress inducible enzyme, is considered as an anti-oxidative and cytoprotective agent. As many studies suggest, HO-1 is highly expressed in the gastrointestinal tract where it is involved in the response to inflammatory processes, which may lead to several diseases such as pancreatitis, diabetes, fatty liver disease, inflammatory bowel disease, and cancer. In this review, we highlight the pivotal role of HO-1 and its downstream effectors in the development of disorders and their beneficial effects on the maintenance of the gastrointestinal tract health. We also examine clinical trials involving the therapeutic targets derived from HO-1 system for the most common diseases of the digestive system.

Drug discovery and formulation development for acute pancreatitis

Acute pancreatitis is a sudden inflammation and only last for a short time, but might lead to a life-threatening emergency. Traditional drug therapy is an essential supportive method for acute pancreatitis treatment, yet, failed to achieve satisfactory therapeutic outcomes. To date, it is still challenging to develop therapeutic medicine to redress the intricate microenvironment promptly in the inflamed pancreas, and more importantly, avoid multi-organ failure. The understanding of the acute pancreatitis, including the causes, mechanism, and severity judgment, could help the scientists bring up more effective intervention and treatment strategies. New formulation approaches have been investigated to precisely deliver therapeutics to inflammatory lesions in the pancreas, and some even could directly attenuate the pancreatic damages. In this review, we will briefly introduce the involved pathogenesis and underlying mechanisms of acute pancreatitis, as well as the traditional Chinese medicine and the new drug option. Most of all, we will summarize the drug delivery strategies to reduce inflammation and potentially prevent the further development of pancreatitis, with an emphasis on the bifunctional nanoparticles that act as both drug delivery carriers and therapeutics.

Macrophage phenotypic switch orchestrates the inflammation and repair/regeneration following acute pancreatitis injury

Background

Impaired or hyperactive pancreas regeneration after injury would cause exocrine insufficiency or recurrent / chronic pancreatitis and potentially carcinogenesis. Macrophages are the most abundant immune cells in the regenerative pancreas, however their phenotype and role remain poorly defined.

Method

Using caerulein-induced acute pancreatitis (AP) model, we examined the dynamic landscape of pancreatic macrophages throughout the acute inflammation to regeneration phases by flow cytometric and RNA-seq analyses. Liposome depletion of macrophages, Il4ra^−/− mice as well as inhibitors were used to elucidate the role and regulatory mechanism of macrophages during pancreatic regeneration.

Findings

We found that M1 macrophages dominated in the pro-inflammatory phase of AP, while M2-like macrophages dominated during pancreas repair/regeneration. Depletion of macrophages at early or late regenerative stage dramatically blocked the acinar-ductal metaplasia (ADM) or delayed inflammation resolution, respectively. Moreover, alternative activation of macrophages was partially dependent on IL-4RA signaling, and ECM/AKT activation in pancreatic macrophages facilitated inflammation resolution during tissue regeneration.

Interpretation

Our findings illustrate a dynamic phenotype and function of macrophages during AP repair/regeneration, helping us better understand the mechanism of pancreatic regeneration and providing clues for novel therapeutic strategy.

Myeloid-specific dopamine D2 receptor signalling controls inflammation in acute pancreatitis via inhibiting M1 macrophage

BACKGROUND AND PURPOSE

Macrophage infiltration and activation is a critical step during acute pancreatitis (AP). We have shown that pancreas-specific D₂ receptor signalling protects against AP severity. As it is unclear to what extent myeloid-specific D₂ receptor mediates AP, we investigated the role of myeloid-specific D₂ receptor signalling in AP.

EXPERIMENTAL APPROACH

Using wild-type and LysM^+/cre D₂ ^fl/fl mice, AP was induced by l-arginine, caerulein and LPS. Murine bone marrow-derived macrophages and human peripheral blood mononuclear cells (PBMCs) were isolated, cultured and then induced to M1 phenotype. AP severity was assessed by measurements of serum amylase and lipase and histological grading. Macrophage phenotype was assessed by flow cytometry and qRT-PCR. NADPH oxidase-induced oxidative stress and NF-κB and NLRP3 inflammasome signalling pathways were also evaluated.

KEY RESULTS

We found that dopaminergic system was activated and dopamine reduced inflammatory cytokine expression in M1-polarized macrophages from human PBMCs. Dopaminergic synthesis was also activated, but D₂ receptor expression was down-regulated in M1-polarized macrophages from murine bone marrows. During AP, myeloid-specific D₂ receptor deletion worsened pancreatic injury, systematic inflammation and promoted macrophages to M1 phenotype. Furthermore, M1 macrophages from LysM^+/cre D₂ ^fl/fl mice exhibited increased NADPH oxidase-induced oxidative stress and enhanced NF-κB and NLRP3 inflammasome activation. D₂ receptor activation inhibited M1 macrophage polarization, oxidative stress-induced NF-κB and NLRP3 inflammasome activation.

CONCLUSION AND IMPLICATIONS

Our data for the first time showed that myeloid-specific D₂ receptor signalling controls pancreatic injury and systemic inflammation via inhibiting M1 macrophage, suggesting D₂ receptor activation might serve as therapeutic target for AP.

Ly-6Chigh inflammatory-monocyte recruitment is regulated by p38 MAPK/MCP-1 activation and promotes ventilator-induced lung injury

Lymphocyte antigen 6Chigh (Ly-6C^high) inflammatory monocytes, as novel mononuclear cells in the innate immune system, participate in infectious diseases. In this study, we investigated the potential role of these monocytes in ventilator-induced lung injury (VILI) and the possible mechanism involved in their migration to lung tissue. Our results showed that mechanical ventilation with high tidal volume (HTV) increased the accumulation of Ly-6C^high inflammatory monocytes in lung tissues and that blocking C‑C chemokine receptor 2 (CCR2) could significantly reduce Ly-6C^high inflammatory-monocyte migration and attenuate the degree of inflammation of lung tissues. In addition, inhibition of p38 mitogen-activated protein kinase (p38 MAPK) activity could decrease the secretion of monocyte chemoattractant protein 1 (MCP-1), which in turn decreased the migration of Ly-6C^high inflammatory monocytes into lung tissue. We also demonstrated that high ventilation caused Ly-6C^high inflammatory monocytes in the bone marrow to migrate into and aggregate in the lungs, creating inflammation, and that the mechanism was quite different from that of infectious diseases. Ly-6C^high inflammatory monocytes might play a pro-inflammatory role in VILI, and blocking their infiltration into lung tissue might become a new target for the treatment of this injury.

Systemic vasoprotection by inhaled carbon monoxide is mediated through prolonged alterations in monocyte/macrophage function

Carbon monoxide (CO) is anti-inflammatory and protective in models of disease. Its actions in vitro are short-lived but are sustained in vivo. We hypothesize that systemic CO can mediate prolonged phenotype changes in vivo, with a focus on macrophages (Mφs). Mφs isolated from CO treated rats responded to lipopolysaccharide (LPS) with increased IL6, IL10 and iNOS expression but decreased TNF. Conditioned media (CM) collected from peritoneal Mφs isolated from CO treated rats stimulated endothelial cell (EC) proliferation versus CM from Mφs from air treated rats. This effect was mediated by Mφ released VEGF and HMGB1. Inhaled CO reduced LPS induced Mφ M1 inflammatory phenotype for up to 5 days. Mitochondrial oxygen consumption in LPS treated Mφs from CO treated mice was preserved compared to LPS treated Mφs from control mice. Finally, transient reduction of inflammatory cells at the time of inhaled CO treatment eliminated the vasoprotective effect of CO in a rodent carotid injury model. Thus, inhaled CO induces a prolonged mixed phenotype change in Mφs, and potentially other inflammatory cells, that contribute to vasoprotection. These findings demonstrate the ability of inhaled CO to modify Mφs in a sustained manner to mediate its therapeutic actions, supporting the translational potential of inhaled CO.

Blockade of CCL2/CCR2 signaling pathway prevents inflammatory monocyte recruitment and attenuates OVA-Induced allergic asthma in mice

Recent studies have reported recruitment of inflammatory monocytes by cytokines including chemokine (C-C motif) ligand 2 (CCL2) are critical in allergic responses. We aimed to investigate the role of inflammatory monocytes and CCL2 in mouse model with ovalbumin (OVA)-induced allergic asthma. Mice were sensitized with OVA to induce allergic asthma. The proportion of inflammatory cells in bronchoalveolar lavage fluid (BALF) and peritoneal lavage fluid (PLF) were measured by flow cytometry. The expression of CCL2 and CCL2 receptor (CCR2) were determined by qPCR and western blot. The concentrations of Type 1 helper T (Th1) and Type 2 helper T (Th2) cytokines in PLF were detected by ELISA. Inflammatory monocytes are recruited in PLF, and expression of CCL2 and CCR2 were elevated in OVA-induced mice. In addition, transfer of CCR2 knockdown inflammatory monocytes decreased the levels of allergic asthma biomarkers. Injection of anti-CCL2 or anti-CCR2 antibody decreased the proportion of eosinophils and inflammatory monocytes in BALF. Blockade of CCL2/CCR2 signaling pathway suppressed the allergen-induced Th2 cytokines and enhanced the levels of Th1-associated cytokines. Blockade of CCL2/CCR2 signaling pathway in sensitization-recruited inflammatory monocytes exhibits protective effects in mouse model of OVA-induced allergic asthma by inhibiting the Th2 inflammatory responses.