Role of substance P and the neurokinin 1 receptor in acute pancreatitis and pancreatitis-associated lung injury

Abstract

Substance P, acting via the neurokinin 1 receptor (NK1R), plays an important role in mediating a variety of inflammatory processes. However, its role in acute pancreatitis has not been previously described. We have found that, in normal mice, substance P levels in the pancreas and pancreatic acinar cell expression of NK1R are both increased during secretagogue-induced experimental pancreatitis. To evaluate the role of substance P, pancreatitis was induced in mice that genetically lack NK1R by administration of 12 hourly injections of a supramaximally stimulating dose of the secretagogue caerulein. During pancreatitis, the magnitude of hyperamylasemia, hyperlipasemia, neutrophil sequestration in the pancreas, and pancreatic acinar cell necrosis were significantly reduced in NK1R-/- mice when compared with wild-type NK1R+/+ animals. Similarly, pancreatitis-associated lung injury, as characterized by intrapulmonary sequestration of neutrophils and increased pulmonary microvascular permeability, was reduced in NK1R-/- animals. These effects of NK1R deletion indicate that substance P, acting via NK1R, plays an important proinflammatory role in regulating the severity of acute pancreatitis and pancreatitis-associated lung injury.

Figures

Figure 1

Effects of NK1R deletion on caerulein-induced pancreatitis. Mice were given 12 hourly injections of caerulein (50 μg/kg, i.p.). One hour after the last caerulein injection, mice were sacrificed, and serum amylase activity, serum lipase activity, pancreatic MPO activity, and acinar-cell necrosis were measured. Values are expressed as a percent of the values obtained for wild-type animals given caerulein. These values (100%) were as follows: serum amylase, 32,865 ± 4,064 units/liter; serum lipase, 4,074 + 380 units/liter; pancreas MPO, (1.73 ± 0.18)-fold increase over saline-treated controls; acinar-cell injury/necrosis, 31.3 ± 3.64% of acinar tissue. Results shown are the mean ± SEM for 10 or more animals in each group. Asterisks indicates P < 0.05 when NK1R−/− animals were compared with NK1R+/+ animals.

Figure 2

Immunohistochemistry of NK1R after caerulein-induced pancreatitis as viewed with confocal microscopy. Mice were given 12 hourly injections of caerulein (50 μg/kg, i.p.). One hour after the last caerulein injection, mice were sacrificed and NK1R expression in the pancreatic cryosections was determined. (A) Section of pancreas from saline-injected NK1R+/+ mouse. (200×.) (B) Section from the same animal with antigen-adsorbed antibody control. (C) Pancreas section from the NK1R+/+ mouse with caerulein-induced pancreatitis. (D) Section from the same animal as C with antigen-adsorbed control. (E) Section of pancreas from saline-injected NK1R−/− mouse. (F) Pancreas section from the NK1R−/− mouse with caerulein-induced pancreatitis.

Figure 3

Morphologic changes of pancreatitis and pancreatitis-associated lung injury. Representative hematoxylin/eosin-stained sections of pancreas (A–C) and lung (D–F) were examined by light microscopy in normal control animals not given caerulein (A and D), in wild-type NK1R+/+ animals given caerulein (B and E), and in NK1R−/− mice given caerulein (C and F).

Figure 4

Effects of NK1R deletion on pancreatitis-associated lung injury. Mice were given 12 hourly injections of caerulein (50 μg/kg, i.p.). One hour after the last caerulein injection, mice were sacrificed and capillary leakage of FITC-albumin and lung MPO activity were measured. Values are expressed as a percent of the value obtained for wild-type animals given caerulein. These values (100%) were as follows: lung MPO activity, 3.06 ± 0.37; FITC-albumin bronchoalveolar lavage fluid to serum ratio 2.13 ± 0.24. Results shown are the mean ± SEM for 10 or more animals in each group. Asterisk indicates P < 0.05 when NK1R−/− animals were compared with NK1R+/+ animals.

Figure 5

Caerulein-stimulated amylase secretion from pancreatic acini. Acini were prepared from NK1R+/+ and NK1R−/− mice and amylase secretion was determined in response to caerulein treatment as described earlier (14). The results shown are from a representative experiment. The experiment was repeated twice with same results.