Tumor Progression Locus-2 Is a Critical Regulator of Pancreatic and Lung Inflammation during Acute Pancreatitis

Abstract

Pancreatic and lung inflammation during acute pancreatitis is a poorly understood, but clinically important, phenomenon. The proto-oncogene Tpl2 (tumor progression locus-2) has recently been shown to have important immunomodulatory effects on some inflammatory processes, but its importance to pancreatitis has not been previously examined. Our studies were designed to (a) define the effects of Tpl2 on pancreatic and lung inflammation during pancreatitis and (b) identify mechanisms and cell types responsible for those effects. We examined pancreatitis-associated Tpl2 effects in wild type and Tpl2 ؊/؊ mice subjected to either secretagogue-induced or bile salt-induced pancreatitis. To determine the myeloid or non-myeloid lineage of cells responsible for the Tpl2 effects, we used Tpl2 ؊/؊ chimeric mice generated by lethal irradiation followed by bone marrow transplantation. Mechanisms responsible for the effects of Tpl2 ablation on caerulein-induced proinflammatory events were evaluated under in vivo and in vitro conditions using the techniques of electrophoretic mobility shift assay, immunoblot analysis, and quantitative reverse transcription-PCR. We found that Tpl2 ablation markedly reduced pancreatic and lung inflammation in these two dissimilar models of pancreatitis, but it did not alter pancreatic injury/necrosis in either model. The reduction in caerulein-induced pancreatic inflammation is dependent upon Tpl2 ablation in non-myeloid cells and is associated with both in vivo and in vitro inhibition of MEK, JNK, and AP-1 activation and the expression of MCP-1, MIP-2, and interleukin-6. Non-myeloid cell expression of Tpl2 regulates pancreatic inflammation during pancreatitis by mediating proinflammatory signals and the generation of neutrophil chemoattracting factors.Severe acute pancreatitis is a devastating disease associated with considerable morbidity and with mortality rates that can reach or exceed 20%. Most of the early deaths during severe pancreatitis are the result of inflammation-related complications including the systemic immune response syndrome and/or pancreatitis-associated lung injury, which clinically presents as the adult respiratory distress syndrome. The events responsible for regulating the inflammatory response in acute pancreatitis, and for coupling pancreatic injury with lung injury, are poorly understood but are of considerable clinical importance because interventions that prevent or limit those responses are likely to reduce the morbidity and mortality of the disease.Tpl2 is a proto-oncogene that has been shown to function as a MAP3K (mitogen-activated protein kinase kinase kinase) and, in this way, to play critical roles in certain inflammatory conditions. We now report the first studies that have examined the possible immunomodulatory effects of Tpl2 in acute pancreatitis. The results of our studies lead us to conclude that Tpl2 acts as a critical regulator of pancreatitis-associated inflammation by mediating the induction of chemoattracting chemokines and that it is Tpl2 expressed b...

Protease-activated Receptor-2 Exerts Contrasting Model-specific Effects on Acute Experimental Pancreatitis

“…the ease of controlled pancreatic duct infusion), and it has not been employed in studies using mice. In recently published studies, however, we have shown that the sodium taurocholate model can, in fact, be adapted for use in mice (3) and that the use of this model in genetically modified mouse strains can provide valuable insights into mechanistic issues related to pancreatitis (4). Virtually all of our observations characterizing this bile salt-in-duced pancreatitis model have been confirmed in a series of studies recently reported by Wittel et al (5).…”

“…Small pancreatic acini (1-10 cells per cluster) used to evaluate calcium transients or lactate dehydrogenase leakage were filtered through a 40-m Nitex filter. For preparation of pancreatic fragments, freshly harvested portions of pancreas were minced, in the absence of collagenase, to create small (Ͻ0.2-mm 3 ) pieces as described previously (4).…”

Regulation and function of TPL-2, an IκB kinase-regulated MAP kinase kinase kinase

“…Analyses of pancreas homogenates demonstrate that caerulein activation of ERK, JNK and AP-1 is dependent on TPL-2 expression, as is the induction of MCP-1 (monocyte chemotactic protein-1), MIP-2 (macrophageinflammatory protein-2) and IL-6 [85]. Thus, TPL-2 may regulate pancreatic inflammation during pancreatitis by mediating proinflammatory signals and the generation of neutrophil chemoattracting factors.…”

“…For example, TPL-2 positively regulates the development of pancreatic and lung inflammation during caerulein-induced acute pancreatitis [85]. By generating bone marrow chimeras, pancreatic inflammation was shown to be controlled by TPL-2 in non-myeloid cells.…”

Cot/tpl2 (MAP3K8) Mediates Myeloperoxidase Activity and Hypernociception following Peripheral Inflammation*

“…Cot/tpl2 is required to process pre-TNF␣ to its mature secreted form in LPS-stimulated macrophages (24). In addition, in different isolated cell types Cot/tpl2 controls the secretion of other cytokines and chemokines such as IL-8, MCP-1, MIP-1␤, KC,10,[24][25][26][27]. Moreover, Cot/tpl2 activation is necessary for the production of PGE 2 in LPS-stimulated macrophages (9).…”