Protective effects of gabexate mesilate on acute pancreatitis induced by tacrolimus (FK-506) in rats in which the pancreas was stimulated by caerulein

Immune cells and immune cell-targeted therapy in chronic pancreatitis

In recent years, studies have attempted to understand the immune cells and mechanisms underlying the pathogenesis of chronic pancreatitis (CP) by constructing a model of CP. Based on these studies, the innate immune response is a key factor in disease pathogenesis and inflammation severity. Novel mechanisms of crosstalk between immune and non-immune pancreatic cells, such as pancreatic stellate cells (PSC), have also been explored. Immune cells, immune responses, and signaling pathways in CP are important factors in the development and progression of pancreatitis. Based on these mechanisms, targeted therapy may provide a feasible scheme to stop or reverse the progression of the disease in the future and provide a new direction for the treatment of CP. This review summarizes the recent advances in research on immune mechanisms in CP and the new advances in treatment based on these mechanisms.

T Lymphocytes: A Promising Immunotherapeutic Target for Pancreatitis and Pancreatic Cancer?

Pancreatic disorders cause a broad spectrum of clinical diseases, mainly including acute and chronic pancreatitis and pancreatic cancer, and are associated with high global rates of morbidity and mortality. Unfortunately, the pathogenesis of pancreatic disease remains obscure, and there is a lack of specific treatments. T lymphocytes (T cells) play a vital role in the adaptive immune systems of multicellular organisms. During pancreatic disease development, local imbalances in T-cell subsets in inflammatory and tumor environments and the circulation have been observed. Furthermore, agents targeting T cells have been shown to reverse the natural course of pancreatic diseases. In this review, we have discussed the clinical relevance of T-cell alterations as a potential outcome predictor and the underlying mechanisms, as well as the present status of immunotherapy targeting T cells in pancreatitis and neoplasms. The breakthrough findings summarized in this review have important implications for innovative drug development and the prospective use of immunotherapy for pancreatitis and pancreatic cancer.

Dendritic cells loaded with FK506 kill T cells in an antigen-specific manner and prevent autoimmunity in vivo

FK506 (Tacrolimus) is a potent inhibitor of calcineurin that blocks IL2 production and is widely used to prevent transplant rejection and treat autoimmunity. FK506 treatment of dendritic cells (FKDC) limits their capacity to stimulate T cell responses. FK506 does not prevent DC survival, maturation, or costimulatory molecule expression, suggesting that the limited capacity of FKDC to stimulate T cells may be due to inhibition of calcineurin signaling in the DC. Instead, we demonstrate that DC inhibit T cells by sequestering FK506 and continuously releasing the drug over several days. T cells encountering FKDC proliferate but fail to upregulate the survival factor bcl-xl and die, and IL2 restores both bcl-xl and survival. In mice, FKDC act in an antigen-specific manner to inhibit T-cell mediated autoimmune arthritis. This establishes that DCs can act as a cellular drug delivery system to target antigen specific T cells.

DOI:http://dx.doi.org/10.7554/eLife.00105.001

Although our health depends on our immune system's ability to recognize and attack foreign material, this same response can cause the body to reject an organ transplant or even to spontaneously attack itself (this is called autoimmune disease). To help prevent rejection, patients who receive donated organs are given immunosuppressant drugs, with a compound called FK506, or Tacrolimus, the most commonly used. However, FK506 can have a number of serious side effects, including high blood pressure, kidney damage and diabetes.

The job of starting an immune response falls in large part to a type of white blood cell called the dendritic cell, which patrols the body in search of cells in trouble—such as those infected with viruses. Dendritic cells are efficient at engulfing dying cells, which they break down and display fragments of on their cell surface. These fragments—which are known as antigens—are presented directly to T cells, which trigger a cascade of additional immune responses leading ultimately to the destruction of infected cells.

In some cases of autoimmune disease, however, T cells begin to mistake the body's own cells for infected cells and to launch attacks against healthy tissue. Evidence suggests that immunosuppressive drugs such as FK506 can help to tone down these inappropriate immune responses. However, the use of FK506 to treat autoimmune disease has been limited by its side effects.

Now, Orange et al. have shown that dendritic cells can be exploited to deliver drugs such as FK506 in a targeted and controlled manner. When the researchers loaded dendritic cells with FK506, they found that the cells sequestered the drug and then released it slowly in quantities that were sufficient to inhibit T-cell responses for at least 72 hr.

Using a mouse model of rheumatoid arthritis—an autoimmune disease characterized by inflammation and destruction of joint tissue—Orange and co-workers demonstrated that their novel drug delivery system could be therapeutically useful. They loaded dendritic cells displaying the antigen that triggers the mouse immune system to attack joint tissue, with FK506, and used the resulting cells to treat arthritic mice. Mice that received these cells showed less severe arthritis than control animals treated with dendritic cells that had not been loaded with FK506. Moreover, the total dose of FK506 that the mice were exposed to was very low, with the result that they showed no evidence of the side effects typically seen with this drug.

This proof-of-concept study suggests that dendritic cells could be used for the gradual and controlled delivery of drugs to specific target cells within the immune system. By precisely targeting relevant immune cells, it should be possible to use much lower drug doses, and thereby reduce side effects. Follow-up studies are now required to determine whether dendritic cells can be used as vehicles for the delivery of other drugs to treat a range of diseases.

DOI:http://dx.doi.org/10.7554/eLife.00105.002

Bile acids induce pancreatic acinar cell injury and pancreatitis by activating calcineurin

Biliary pancreatitis is the leading cause of acute pancreatitis in both children and adults. A proposed mechanism is the reflux of bile into the pancreatic duct. Bile acid exposure causes pancreatic acinar cell injury through a sustained rise in cytosolic Ca(2+). Thus, it would be clinically relevant to know the targets of this aberrant Ca(2+) signal. We hypothesized that the Ca(2+)-activated phosphatase calcineurin is such a Ca(2+) target. To examine calcineurin activation, we infected primary acinar cells from mice with an adenovirus expressing the promoter for a downstream calcineurin effector, nuclear factor of activated T-cells (NFAT). The bile acid taurolithocholic acid-3-sulfate (TLCS) was primarily used to examine bile acid responses. TLCS caused calcineurin activation only at concentrations that cause acinar cell injury. The activation of calcineurin by TLCS was abolished by chelating intracellular Ca(2+). Pretreatment with 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (acetoxymethyl ester) (BAPTA-AM) or the three specific calcineurin inhibitors FK506, cyclosporine A, or calcineurin inhibitory peptide prevented bile acid-induced acinar cell injury as measured by lactate dehydrogenase leakage and propidium iodide uptake. The calcineurin inhibitors reduced the intra-acinar activation of chymotrypsinogen within 30 min of TLCS administration, and they also prevented NF-κB activation. In vivo, mice that received FK506 or were deficient in the calcineurin isoform Aβ (CnAβ) subunit had reduced pancreatitis severity after infusion of TLCS or taurocholic acid into the pancreatic duct. In summary, we demonstrate that acinar cell calcineurin is activated in response to Ca(2+) generated by bile acid exposure, bile acid-induced pancreatic injury is dependent on calcineurin activation, and calcineurin inhibitors may provide an adjunctive therapy for biliary pancreatitis.

Action of tacrolimus in arginine induced experimental acute pancreatitis

OBJECTIVE

To determine whether tacrolimus administered to rats, in the presence of pancreatitis induced by L-Arginine, interferes with the serum levels of amylase and glucose and the histological pattern of the pancreatic parenchyma.

METHODS

Forty Wistar rats were divided into four groups with 10 rats each: control group (C), tacrolimus group (T), pancreatitis group (P) and pancreatitis-tacrolimus group (PT). We evaluated serum levels of amylase, glucose, and tacrolimus and made histological assessments of the pancreas. Induction of pancreatitis was made by inoculation of L-Arginine at a dose of 500 mg/100g body weight intraperitoneally, and tacrolimus treatment at a dose of 1ìg/kg subcutaneously for four days.

RESULTS

Serum amylase was higher (p = 0.0000) in groups PT, P and T than in the control group. The PT group mean was higher (p = 0.0009) than in the T group, but did not differ (p = 0.6802) from the average of the P group. There was no difference between groups P and T (p = 0.2568). Neither in mean blood glucose between the groups (p = 0.4920); serum levels of tacrolimus were similar in PT and T groups (p = 0.7112). There were no histological changes in groups T and C and no hemorrhage in the pancreas of rats in groups P and PT. In group P, there was no edema in 30%, mild edema in 20% and in 50%, moderate; as for inflammatory infiltration, it was moderate in 80% and absent in 20%, and atrophy of the parenchyma was moderate in 60% and severe in 40%. In the PT group, there was edema, inflammatory infiltration or atrophy in the pancreas in all rats.

CONCLUSION

Treatment with Tacrolimus induced an increase in serum amylase in normal mice, but did not affect blood glucose or the histological pattern of the pancreatic parenchyma. In the presence of pancreatitis induced by L-Arginine tacrolimus induced edema, inflammatory infiltration and more severe atrophy in the pancreatic parenchyma.

Protease activation during in vivo pancreatitis is dependent on calcineurin activation

The premature activation of digestive proenzymes, specifically proteases, within the pancreatic acinar cell is an early and critical event during acute pancreatitis. Our previous studies demonstrate that this activation requires a distinct pathological rise in cytosolic Ca(2+). Furthermore, we have shown that a target of aberrant Ca(2+) in acinar cells is the Ca(2+)/calmodulin-dependent phosphatase calcineurin (PP2B). In this study, we hypothesized that PP2B mediates in vivo protease activation and pancreatitis severity. To test this, pancreatitis was induced in mice over 8 h by administering hourly intraperitoneal injections of the cholecystokinin analog caerulein (50 microg/kg). Treatment with the PP2B inhibitor FK506 at 1 and 8 h after pancreatitis induction reduced trypsin activities by greater than 50% (P < 0.005). Serum amylase and IL-6 was reduced by 86 and 84% relative to baseline (P < 0.0005) at 8 h, respectively. Histological severity of pancreatitis, graded on the basis of pancreatic edema, acinar cell vacuolization, inflammation, and apoptosis, was reduced early in the course of pancreatitis. Myeloperoxidase activity from both pancreas and lung was reduced by 93 and 83% relative to baseline, respectively (P < 0.05). These data suggest that PP2B is an important target of the aberrant acinar cell Ca(2+) rise associated with pathological protease activation and pancreatitis.

Caerulein-induced intracellular pancreatic zymogen activation is dependent on calcineurin

Aberrant cytosolic Ca(2+) flux in pancreatic acinar cells is critical to the pathological pancreatic zymogen activation observed in acute pancreatitis, but the downstream effectors are not known. In this study, we examined the role of Ca(2+)-activated protein phosphatase 2B (or calcineurin) in zymogen activation. Isolated pancreatic acinar cells were stimulated with supraphysiological caerulein (100 nM) with or without the calcineurin inhibitors FK506 or cell-permeable calcineurin inhibitory peptide (CiP). Chymotrypsin activity was measured as a marker of zymogen activation, and the percent amylase secretion was used as a measure of enzyme secretion. Cytosolic Ca(2+) changes were recorded in acinar cells loaded with the intermediate Ca(2+)-affinity dye fluo-5F using a scanning confocal microscope. A 50% reduction in chymotrypsin activity was observed after pretreatment with 1 microM FK506 or 10 microM CiP. These pretreatments did not affect amylase secretion or the rise in cytosolic Ca(2+) after caerulein stimulation. These findings suggest that calcineurin mediates caerulein-induced intra-acinar zymogen activation but not enzyme secretion or the initial caerulein-induced cytosolic Ca(2+) signal.

Biochemistry and biology of SPINK-PSTI and monitor peptide

This article summarizes structural and functional properties of pancreatic secretory trypsin inhibitor (PSTI), which has been identified in many species. Its prominent role is to protect the pancreas from prematurely activated trypsinogen before entry into the duodenum. In the rat there are two isoforms, one of which is PSTI-I, a 61-amino acid peptide involved in the feedback regulation of pancreatic enzymes. Independent investigations in neoplastic diseases led to the discovery of tumor-associated trypsin inhibitor,which is identical to PSTI.

Ciclosporin aggravates tissue damage in ischemia reperfusion-induced acute pancreatitis

OBJECTIVES

Ischemia reperfusion (I/R)-associated early graft pancreatitis is a major complication after pancreas transplantation. The influence of immunosuppressants on graft pancreatitis remains unclear. The aim of this study was to evaluate ciclosporin and tacrolimus in experimental pancreatic I/R.

METHODS

Moderate pancreatitis was induced in rats by I/R injury. Animals were assigned to 4 groups: (1) control without I/R, (2) I/R without therapy, (3) I/R + ciclosporin, or (4) I/R + tacrolimus. After 24 hours, pancreatic damage was evaluated by amylase, endothelin 1, thromboxane A2, and histology. Additionally, microcirculation was evaluated 12 hours after reperfusion by intravital microscopy.

RESULTS

I/R significantly increased amylase compared with controls, with maximum levels after ciclosporin treatment. Histology showed comparable tissue injury in control and tacrolimus-treated animals. Ciclosporin-treated animals developed significantly (P < 0.05) more inflammation and necrosis compared with the other groups. Erythrocyte velocity evaluated by intravital microscopy was reduced in all animals after I/R. This was significantly pronounced after ciclosporin application. There was a significant increase of adherent leukocytes and platelets in ciclosporin-treated animals compared with both other groups.

CONCLUSIONS

Tacrolimus does not negatively influence I/R-induced pancreatitis, whereas ciclosporin aggravates pancreatic tissue damage after I/R. These effects should be evaluated in the clinical setting of pancreas transplantation.

Role of T cells in development of chronic pancreatitis in male Wistar Bonn/Kobori rats: effects of tacrolimus

We assessed T cell association with acinar cell apoptosis and a preventive effect of tacrolimus, a T cell suppressant, on the development of chronic pancreatitis in male Wistar Bonn/Kobori rats. At 15 wk, cellular infiltrates composed of F4/80-positive cells (monocytes/macrophages), CD4-positive cells, and CD8-positive cells were extensive in the interlobular connective tissue and parenchyma. In particular, CD8-positive cells invaded pancreatic lobules and formed close associations with acinar cells, some of which demonstrated features of apoptosis. At 20 wk, CD8-positive cells were still abundant in the fibrotic tissue formed with loss of acinar cells. Repeated subcutaneous injection of 0.1 mg x kg(-1) x day(-1) but not 0.025 mg x kg(-1) x day(-1) of tacrolimus for 10 wk completely prevented the occurrence of acinar cell apoptosis, infiltration of CD4- and CD8-positive cells, and development of pancreatitis at the age of 20 wk, but these maneuvers did not recover the decreased plasma corticosterone levels, which may be responsible for the development of disease. We demonstrated that T cells, possibly CD8-positive cells, are involved in inducing apoptosis of acinar cells, raising the possibility that tacrolimus might find clinical application in the treatment of autoimmune chronic pancreatitis.

Alcohol and the pancreas

Alcoholic pancreatitis is a major, often lethal complication of alcohol abuse. Until recently it was generally accepted that alcoholic pancreatitis was a chronic disease from the outset. However, there is now emerging evidence in favour of the necrosis-fibrosis hypothesis that alcoholic pancreatitis begins as an acute process and that repeated acute attacks lead to chronic pancreatitis, resulting in exocrine and endocrine failure. Over the past 10-15 years, the focus of research into the pathogenesis of alcoholic pancreatitis has shifted from possible sphincteric and ductular abnormalities to the acinar cell itself which has increasingly been implicated as the initial site of injury. Recent studies have shown that the acinar cell can metabolize alcohol at rates comparable to those observed in hepatocytes. In addition, it has been demonstrated that alcohol and its metabolites exert direct effects on the pancreatic acinar cell which may promote premature digestive enzyme activation and oxidant stress. The challenge remains to identify predisposing and triggering factors in this disease.