Protective effects of erythropoietin against acute lung injury in a rat model of acute necrotizing pancreatitis

Abstract

Aim: To investigate the effect of exogenous erythro-poietin (EPO) administration on acute lung injury (ALI) in an experimental model of sodium taurodeoxycholate- induced acute necrotizing pancreatitis (ANP).

Methods: Forty-seven male Wistar albino rats were randomly divided into 7 groups: sham group (n = 5), 3 ANP groups (n = 7 each) and 3 EPO groups (n = 7 each). ANP was induced by retrograde infusion of 5% sodium taurodeoxycholate into the common bile duct. Rats in EPO groups received 1000 U/kg intramuscular EPO immediately after induction of ANP. Rats in ANP groups were given 1 mL normal saline instead. All animals were sacrificed at postoperative 24 h, 48 h and 72 h. Serum amilase, IL-2, IL-6 and lung tissue malondialdehyde (MDA) were measured. Pleural effusion volume and lung/body weight (LW/BW) ratios were calculated. Tissue levels of TNF-alpha, IL-2 and IL-6 were screened immunohistochemically. Additionally, ox-LDL accumulation was assessed with immune-fluorescent staining. Histopathological alterations in the lungs were also scored.

Results: The mean pleural effusion volume, calculated LW/BW ratio, serum IL-6 and lung tissue MDA levels were significantly lower in EPO groups than in ANP groups. No statistically significant difference was observed in either serum or tissue values of IL-2 among the groups. The level of tumor necrosis factor-alpha (TNF-alpha) and IL-6 and accumulation of ox-LDL were evident in the lung tissues of ANP groups when compared to EPO groups, particularly at 72 h. Histopathological evaluation confirmed the improvement in lung injury parameters after exogenous EPO administration, particularly at 48 h and 72 h.

Conclusion: EPO administration leads to a significant decrease in ALI parameters by inhibiting polymorphonuclear leukocyte (PMNL) accumulation, decreasing the levels of proinflammatory cytokines in circulation, preserving microvascular endothelial cell integrity and reducing oxidative stress-associated lipid peroxidation and therefore, can be regarded as a cytoprotective agent in ANP-induced ALI.

Figures

Figure 1

Values of pleural effusion volumes (A) and calculated LW/BW ratios (B) (mean ± SD).

Figure 2

Values of MDA in lung tissue (mean ± SD).

Figure 3

Light microscopic view of immunohistochemical staining for intracellular accumulations of TNF-α and IL-6 in the lung sections of ANP groups (A and B) and EPO groups (C and D) at 72 h. Arrows indicate the significantly positive staining in ANP groups (A and B) and less intensive immnunohistochemical staining in EPO groups (C and D).

Figure 4

Lung tissue sections from EPO groups and ANP groups showing no fluorescent staining (A) and positive fluorescent staining (B) at 72 h. Arrows indicate the accumulation areas of ox-LDL in the lung.

Figure 5

Mean values of alveolar distension and collapse index (A), alveolar edema index (percentage of the alveolar lumen filled with edema) (B), alveolar cellularity index (C) and polymorphonuclear cell index (D) obtained in the seven groups.

Figure 6

Light microscopy revealing significant lung injury-associated alveolar septal thickening, interstitial edema, infiltration of inflammatory cells, destruction of alveolar wall (emphysema), and microabscess formation in ANP groups at 48 h (A) and 72 h (B), and attenuation of inflammatory reaction, edema and emphysema in EPO groups at 48 h (C) and 72 h (D).

Figure 7

Light microscopic view of pancreatitis with severe fatty necrosis.