Beneficial effects of Mn(III)tetrakis (4-benzoic acid) porphyrin (MnTBAP), a superoxide dismutase mimetic, in zymosan-induced shock

Abstract

1 The therapeutic efficacy of Mn(III)tetrakis (4-benzoic acid) porphyrin (MnTBAP), a novel superoxide dismutase mimetic which scavenges peroxynitrite, was investigated in rats subjected to shock induced by peritoneal injection of zymosan. 2 Our data show that MnTBAP (given at 1, 3 and 10 mg kg-1 intraperitoneally, 1 and 6 h after zymosan injection) significantly reduce in dose dependent manner the development of peritonitis (peritoneal exudation, high nitrate/nitrite and peroxynitrite plasma levels, leukocyte infiltration and histological examination). 3 Furthermore, our data suggest that there is a reduction in the lung, small intestine and liver myeloperoxidase (MPO) activity and lipid peroxidation activity from MnTBAP-treated rats. 4 MnTBAP also reduced the appearance of nitrotyrosine immunoreactivity in the inflamed tissues. 5 Furthermore, a significant reduction of suppression of mitochondrial respiration, DNA strand breakage and reduction of cellular levels of NAD+ was observed in ex vivo macrophages harvested from the peritoneal cavity of zymosan-treated rat. 6 In vivo treatment with MnTBAP significantly reduced in a dose-dependent manner peroxynitrite formation and prevented the appearance of DNA damage, the decrease in mitochondrial respiration and the loss of cellular levels of NAD+. 7 In conclusion our results showed that MnTBAP was effective in preventing the development of zymosan-induced shock.

Figure 1

Data represent values at 18 h after vehicle or zymosan administration (500 mg kg⁻¹ i.p.). (A) Exudate volumes; (B) leukocytes accumulation; (C) plasma NOx levels; (D) plasma peroxynitrite production. MnTBAP (1, 3 and 10 mg kg⁻¹, i.p. 1 and 6 h after zymosan) treatment induced in a dose dependent manner a significant decrease of peritoneal exudate, leukocyte migration and NOx and peroxynitrite levels. Data are means±s.e.mean of 10 rats for each group. ^*P<0.01 versus sham. °P<0.01 versus zymosan.

Figure 2

Immunohistochemical localization of nitrotyrosine in the rat lung. Eighteen following zymosan injection, nitrotyrosine immunoreactivity was localized mainly in vascular wall (A), bronchial (B) and macrophages (C). There was no detectable immunostaining in the lungs of zymosan-treated rats when rats were treated with MnTBAP (D). Original magnification: ×100.

Figure 3

Immunohistochemical localization of nitrotyrosine in the rat small intestine. Positive staining was found in the intestine from zymosan-treated rats (A). There was no detectable immunostaining in the intestine of zymosan-treated rats when they were treated with MnTBAP (10 mg kg⁻¹, i.p. 1 and 6 h after zymosan) (B). Original magnification: A-B 100×; C-D 200×.

Figure 4

Myeloperoxidase (MPO) activity (A) and malondialdehyde (MDA) (B) in the lungs, small intestine and liver of zymosan-treated rats. MPO activity and MDA levels were significantly increased in the lung, small intestine and liver of the zymosan-treated rats in comparison to sham ras MnTBAP (1, 3 and 10 mg kg⁻¹, i.p. 1 and 6 h after zymosan) treatment significantly reduce in dose dependent manner the zymosan-induced increase in MPO activity and MDA levels. Each value is the mean±s.e.mean for n=10. ^*P<.01 versus sham; °P<.01 versus zymosan.

Figure 5

Lung sections from a zymosan-treated rat revealed inflammatory infiltration of neutrophil, macrophage and plasma cells (A). Lung sections from zymosan-treated rat that received MnTBAP (10 mg kg⁻¹, i.p. 1 and 6 h after zymosan) demonstrate reduced inflammatory infiltration (B). Sections are representative of n=4 rats examined for each group. Original magnification: ×100.

Figure 6

Distal ileum section from a zymosan-treated rat showed inflammatory infiltration of neutrophil, lymphocytes and plasma cells extending through the wall and concentrated below the epithelial layer (A). Distal ileum from zymosan-treated rat that received MnTBAP (10 mg kg⁻¹, i.p. 1 and 6 h after zymosan) showed reduced zymosan-induced inflammatory infiltration (B). Original magnification: ×100.

Figure 7

Plasma level of alanine aminotransferase (A), bilirubin (B), lactade dehydrogenase (C) and alkaline phosphatase (D). Zymosan-treated rats exhibited a dysmetabolic change. Administration of MnTBAP (10 mg kg⁻¹, i.p. 1 and 6 h after zymosan) prevented the metabolic modification. Each value is the mean±s.e.mean for n=10. ^*P<.01 versus sham; °P<.01 versus zymosan.

Figure 8

Effect of MnTBAP treatment on zymosan-induced mortality. n=10 rats for each group. ^*P<0.01 versus zymosan.

Figure 9

Nitrate/nitrite production (A), peroxynitrite production (B), DNA single strand breakage (C), reduction of mitochondrial respiration (D) and cellular levels of NAD⁺ (E) in peritoneal macrophages harvested 18 h after zymosan administration. ^*P<0.01 versus macrophages from control rats; °P<0.01 represents protective effects of MnTBAP.