Opsonin receptor expression on peritoneal exudative and circulatory neutrophils in murine acute pancreatitis

Identification of novel immune-related targets mediating disease progression in acute pancreatitis

Introduction

Acute pancreatitis (AP) is an inflammatory disease with very poor outcomes. However, the order of induction and coordinated interactions of systemic inflammatory response syndrome (SIRS) and compensatory anti-inflammatory response syndrome (CARS) and the potential mechanisms in AP are still unclear.

Methods

An integrative analysis was performed based on transcripts of blood from patients with different severity levels of AP (GSE194331), as well as impaired lung (GSE151572), liver (GSE151927) and pancreas (GSE65146) samples from an AP experimental model to identify inflammatory signals and immune response-associated susceptibility genes. An AP animal model was established in wild-type (WT) mice and Tlr2-deficient mice by repeated intraperitoneal injection of cerulein. Serum lipase and amylase, pancreas impairment and neutrophil infiltration were evaluated to assess the effects of Tlr2 in vivo.

Results

The numbers of anti-inflammatory response-related cells, such as M2 macrophages (P = 3.2 × 10^-3), were increased with worsening AP progression, while the numbers of pro-inflammatory response-related cells, such as neutrophils (P = 3.0 × 10^-8), also increased. Then, 10 immune-related AP susceptibility genes (SOSC3, ITGAM, CAMP, FPR1, IL1R1, TLR2, S100A8/9, HK3 and MMP9) were identified. Finally, compared with WT mice, Tlr2-deficient mice exhibited not only significantly reduced serum lipase and amylase levels after cerulein induction but also alleviated pancreatic inflammation and neutrophil accumulation.

Discussion

In summary, we discovered SIRS and CARS were stimulated in parallel, not activated consecutively. In addition, among the novel susceptibility genes, TLR2might be a novel therapeutic target that mediates dysregulation of inflammatory responses during AP progression.

Characteristic pancreatic and splenic immune cell infiltration patterns in mouse acute pancreatitis

BACKGROUND

A systemic evaluation of immune cell infiltration patterns in experimental acute pancreatitis (AP) is lacking. Using multi-dimensional flow cytometry, this study profiled infiltrating immune cell types in multiple AP mouse models.

METHODS

Three AP models were generated in C57BL/6 mice via cerulein (CAE) injection, alcohol and palmitoleic acid (EtOH + POA) injection, and alcohol diet feeding and cerulein (EtOH + CAE) injection. Primary pancreatic cells and splenocytes were prepared, and multi-dimensional flow cytometry was performed and analyzed by manual gating and computerized PhenoGraph, followed by visualization with t-distributed stochastic neighbor embedding (t-SNE).

RESULTS

CAE treatment induced a time-dependent increase of major innate immune cells and a decrease of follicular B cells, and T^CD4+ cells and the subtypes in the pancreas, whereas elicited a reversed pattern in the spleen. EtOH + POA treatment resulted in weaker effects than CAE treatment. EtOH feeding enhanced CAE-induced amylase secretion, but unexpectedly attenuated CAE-induced immune cell regulation. In comparison with manual gating analysis, computerized analysis demonstrated a remarkable time efficiency and reproducibility on the innate immune cells and B cells.

CONCLUSIONS

The reverse pattern of increased innate and decreased adaptive immune cells was consistent in the pancreas in CAE and EtOH + POA treatments. Alcohol feeding opposed the CAE effect on immune cell regulation. Together, the immune profiling approach utilized in this study provides a better understanding of overall immune responses in AP, which may facilitate the identification of intervention windows and new therapeutic strategies. Computerized analysis is superior to manual gating by dramatically reducing analysis time.

Effects of Granulocyte Colony-Stimulating Factor on Opsonin Receptor Expression and Neutrophil Antibacterial Activity in a Mouse Model of Severe Acute Pancreatitis

The antimicrobial function of neutrophils, which is dependent on opsonin receptors, deteriorates in severe acute pancreatitis (SAP). Granulocyte colony-stimulating factor (G-CSF) putatively enhanced levels of the opsonin receptors CD11b and CD32/16 in healthy human subjects, and provided protection against infection in animal models of SAP. A statistically convincing study of the effect of G-CSF on CD32/16 expression in an SAP model is lacking. We used a mouse model of SAP to investigate the association between G-CSF administration and CD32/16 levels on neutrophils and bacterial translocation. G-CSF or saline was subcutaneously injected into SAP-induced mice. The pancreases were histologically examined, and leukocytes were stained to count neutrophils. The expression of CD11b and CD32/16 on neutrophils was measured by flow cytometry, and bacterial translocation was observed by bacterial culture. The numbers of CD11b and CD32/16-positive neutrophils were significantly elevated in the SAP mice treated with G-CSF, and the mean fluorescence intensities of these receptors on neutrophils were significantly elevated. Bacterial translocations to cavity organs were suppressed from 17% to 6% by G-CSF treatment. Our results indicated that the number of neutrophils significantly increased with increasing expression of CD11b and CD32/16 and their mean fluorescence intensities (MFIs). This inhibited bacterial translocation to other organs. These results are in accord with other studies in SAP dogs and SAP mice. Our findings suggest that G-CSF was effective in protecting against bacterial infection in SAP mice.

Complement in Pancreatic Disease-Perpetrator or Savior?

The complement system is a major pillar of the humoral innate immune system. As a first line of defense against pathogens, it mediates early inflammatory response and links different branches of humoral and cellular immunity. Disorders affecting the exocrine pancreas, such as acute pancreatitis, potentially lead to a life-threatening systemic inflammatory response with aberrant activation of complement and coagulation cascades. Pancreatic proteases can activate key effectors of the complement system, which in turn drive local and systemic inflammation. Beyond that, the extent of pancreas–complement interaction covers complex pro- and anti-inflammatory mechanisms, which to this day remain to be fully elucidated. This review provides a comprehensive overview of the pathophysiological role of complement in diseases of the exocrine pancreas, based on existing experimental and clinical data. Participation of complement in acute and chronic pancreatitis is addressed, as well as its role in tumor immunology. Therapeutic strategies targeting complement in these diseases have long been proposed but have not yet arrived in the clinical setting.

ERK5 activation in macrophages promotes efferocytosis and inhibits atherosclerosis

BACKGROUND

Efferocytosis is a process by which dead and dying cells are removed by phagocytic cells. Efferocytosis by macrophages is thought to curb the progression of atherosclerosis, but the mechanistic insight of this process is lacking.

METHODS AND RESULTS

When macrophages were fed apoptotic cells or treated with pitavastatin in vitro, efferocytosis-related signaling and phagocytic capacity were upregulated in an ERK5 activity-dependent manner. Macrophages isolated from macrophage-specific ERK5-null mice exhibited reduced efferocytosis and levels of gene and protein expression of efferocytosis-related molecules. When these mice were crossed with low-density lipoprotein receptor(-/-) mice and fed a high-cholesterol diet, atherosclerotic plaque formation was accelerated, and the plaques had more advanced and vulnerable morphology.

CONCLUSIONS

Our results demonstrate that ERK5, which is robustly activated by statins, is a hub molecule that upregulates macrophage efferocytosis, thereby suppressing atherosclerotic plaque formation. Molecules that upregulate ERK5 and its signaling in macrophages may be good drug targets for suppressing cardiovascular diseases.

Effect of dexamethasone on peripheral blood leukocyte immune response in bile-pancreatic duct obstruction-induced acute pancreatitis

Our aim was to analyze the effects of dexamethasone (Dx) (1mg/kg), prophylactically or therapeutically administered, on the inflammatory response triggered by peripheral blood leukocytes during acute pancreatitis (AP) induced in rats by bile-pancreatic duct obstruction (BPDO) and their consequences in the progress of the disease. Flow cytometry was used to analyze the distribution of the major leukocyte populations, the CD45 expression and the activated state of monocytes as reflected by the membrane-bound intercellular adhesion molecule-1 (ICAM-1) and the production of tumor necrosis factor-alpha (TNF-alpha) and monocyte chemoattract protein-1 (MCP-1) in response to lipopolysaccaride (LPS). Interleukin-6 (IL-6) plasma levels, pancreatic fluid content and histology of pancreas sections were also evaluated. Dx, given either before or after AP, blunted the monocyte increase induced by BPDO-induced AP, but did not change lymphocyte and neutrophil counts. Membrane-bound ICAM-1 expression did not vary in circulating monocytes during BPDO, either in Dx-treated or non-treated rats. Both Dx treatments inhibited TNF-alpha and MCP-1 production in non-stimulated and LPS-stimulated monocytes, whose response was found to be higher than in controls from early AP. Leukocyte CD45 expression was found to be reduced in rats with AP and shifted to control values in Dx-post-treated rats. Cytokinemia as well as pancreatic edema and leukocyte infiltration found in BPDO rats were reduced by Dx given either before or after AP. We conclude that prophylactic and therapeutic Dx treatments inhibited the inflammatory response triggered by circulating leukocytes in rats with BPDO-induced AP, thus contributing to reducing the severity of the disease.

The role of Rac1 and Rac2 in bacterial killing

The small Rho guanosine triphosphatases (GTPases) Rac1 and Rac2 have distinct roles in regulating neutrophil chemotaxis; however, little is known about their possible unique roles in mediating bacterial killing. To elucidate the relative roles of Rac1 and Rac2 in regulating neutrophil-mediated bacterial killing, we utilized the previously described mice model in which mouse neutrophils are deficient in either Rac1, Rac2, or both isoforms. We demonstrate here that while both Rac isoforms are required for normal neutrophil chemotaxis and bacterial killing, they have non-overlapping roles in bacterial phagocytosis and NADPH oxidase function.

Cholecystokinin blockade alters the systemic immune response in rats with acute pancreatitis

Acute pancreatitis (AP) is characterized by initial pancreatic injury resulting from the activation of digestive enzymes and, later, widespread inflammation to distant organs. The aim of this study was to study whether the time-course of inflammatory events during AP induced by bile-pancreatic duct obstruction (BPDO) varies after lowering the acinar enzyme content by L364,718 (0.1 mg/kg/day) administration over 7 days before inducing AP. Flow cytometric immunophenotyping was used to analyse the following at different AP stages: distribution of major circulating leucocyte subsets, activation state of circulating neutrophils and monocytes as reflected by CD11b expression and tumour necrosis factor-alpha (TNF-alpha) production and the contribution of T-cell-derived pro-(TNF-alpha) and anti-(IL-10) inflammatory mediators. TNF-alpha plasma levels and neutrophil infiltration in pancreas and lung were also measured. At early BPDO times, L364,718 treatment partially inhibited leukocytosis and increase in peripheral blood neutrophils and monocytes as well as TNF-alpha expression by monocytes. However, from 6 h onwards after BPDO, L364,718 treatment was unable to prevent either pancreatic and lung neutrophil infiltration or the release of TNF-alpha from activated monocytes. By its action on circulating lymphocytes, L364,718 treatment enhanced the severity of the inflammatory response induced by BPDO. Peripheral blood lymphocytes were recruited from earlier BPDO times, and 12 h after BPDO, T cells displayed a significantly higher reserve of TNF-alpha able to be released under stimulation but lower functional reserve of interleukin-10 (IL-10) than observed in untreated rats. It is concluded that lowering the acinar enzyme content through L364,718 treatment prevents earlier systemic immune events in BPDO-induced AP. However, at the point of maximal injury, the inflammatory response became pronounced, largely due to the role played by activated T lymphocytes.

Expression of IL-6 and integrin family cell adhesion molecules in acute necrotizing pancreatitis complicated with multiple organ injury in rats

AIM

To detect the expression of integrin family cellular adhesion molecules LFA-1, Mac-1 and IL-6 in acute necrotizing pancreatitis complicated with multiple organ injury.

METHODS

The flow cytometer was used to detect the expression of LFA-1 and Mac-1 on leukocyte and the radio-immunity to detect the IL-6 in acute necrotizing pancreatitis of rats at different time points.

RESULTS

The expression of LFA-1 and Mac-1 increased significantly in acute pancreatitis group compared with that in control group at all time points (P<0.01), i.e.: LFA-1: 1 h, 7.6±0.4 vs 22.7±1.6; 3 h, 7.9±0.5 vs 26.7±5.5; 6 h, 13.5±1.8 vs 30.3±1.6; 12 h, 9.7±0.7 vs 20.3±4.2; 24 h, 10.1±1.1 vs 15.9±0.7. Mac-1: 1 h, 6.2±1.1 vs 7.0±2.5; 3 h, 6.3±0.8 vs 36.0±1.5; 6 h, 7.9±1.2 vs 27.1±1.4; 12 h, 6.4±0.4 vs 22.5±2.1; 24 h, 7.1±0.4 vs 20.6±1.6. Expression of IL-6 increased significantly in acute pancreatitis group compared with that in control group, i.e.: 1 h, 65.6±3.2 vs 72.4±4.0 (P<0.05); 3 h, 68.2±5.5 vs 155.3±16.3 (P<0.01); 6 h, 69.3±2.6 vs 229.2±16.4 (P<0.01); 12 h, 73.4±2.6 vs 287.7±13.9 (P<0.01); 24 h, 76.9±3.3 vs 289.5±16.1 (P<0.01). Morphological examination demonstrated that inflammatory cells, insterstitial edema, interstitial hemorrhage, desquamation and disintegration occurred in the lungs and kidneys.

CONCLUSION

IL-6, LFA-1 and Mac-1 may play the very active role in acute pancreatitis.

Contribution of circulating leukocytes to cytokine production in pancreatic duct obstruction-induced acute pancreatitis in rats

Little information is available regarding the role of circulating leukocytes in the pathogenesis of acute pancreatitis (AP). Our aim was to explore the time-course of the potential role of inflammatory peripheral blood (PB) cells during AP induced in rats by pancreatic duct obstruction (PDO). Flow cytometry immunophenotyping was used to analyse the distribution of the major circulating leukocyte subsets, the activation state of circulating monocytes as reflected by both CD11b expression and TNF-alpha production and the relative contribution of T-cell derived pro- (TNF-alpha) and anti- (IL-10) inflammatory mediators at different stages of PDO-induced AP. A progressive increase in PB neutrophils and monocytes was observed up to 6h after PDO whereas lymphocytes, as well as CD4(+) and CD8(+) T-cell subsets, rose as early as 1.5 h after PDO and decreased thereafter. Monocytes were activated in PB from 6 h after inducing AP as reflected by increases in both CD11b expression and spontaneous TNF-alpha production; nevertheless, they showed the capability of producing TNF-alpha at earlier AP stages by lipopolysaccharide (LPS) stimulation. In contrast, T-cells were unable to produce TNF-alpha during AP neither spontaneously nor after stimulation with PMA/Ionomycin. Therefore, only PB monocytes contribute to increase TNF-alpha levels in plasma as observed from 12 h onwards after inducing AP. Interleukin-10 was produced by T-cells 6 h after PDO only after PMA/Ionomycin stimulation. We conclude that systemic inflammatory events are triggered off at early stages of PDO-induced AP, with the activation of circulating monocytes, though not T-cells, playing a central role.

Peritoneal inflammatory cells in acute pancreatitis: Relationship of infiltration dynamics and cytokine production with severity of illness

BACKGROUND

The purpose of this study was to clarify the still poorly understood dynamics of peritoneal inflammatory cells (PICs) in acute pancreatitis.

METHODS

Acute pancreatitis of 3 different degrees of severity was induced in male Wistar rats. Peritoneal lavage was performed at 1, 6, 12, and 24 hours after the induction, and the fluids collected were analyzed for the number and subpopulation of PICs. The levels of apoptosis and necrosis, cytokines, and bacterial infection were also investigated.

RESULTS

The number of PICs was increased in mild and moderate pancreatitis, and the infiltration of inflammatory cells had occurred. In severe pancreatitis, the number of PICs increased until 6 hours after the induction, but thereafter the number decreased. Infiltration of neutrophils occurred 6 hours after the induction, but it was not sustained thereafter and infiltration of peritoneal macrophages did not occur. Cytokines in the lavage fluid increased in all 3 models during the first 6 hours after the induction. Subsequently, cytokines were reduced in mild and moderate pancreatitis but significantly increased in severe pancreatitis. The level of bacterial infection increased according to the severity.

CONCLUSIONS

The relationship between the PIC dynamics and cytokine levels in severe pancreatitis is very different from that observed in mild or moderate pancreatitis.