Polydeoxyribonucleotide Exerts Therapeutic Effect by Increasing VEGF and Inhibiting Inflammatory Cytokines in Ischemic Colitis Rats

Abstract

Ischemic colitis is resulted from an inadequate blood supply to a segment or entire colon. Polydeoxyribonucleotide (PDRN), extracted from salmon sperm, has been reported to exert anti-inflammatory and anti-ischemic effects through the adenosine A_2A receptor (A_2AR). We investigated whether PDRN possesses therapeutic effectiveness on ischemic colitis rats. Ischemic colitis was induced by selective devascularization. The skin temperature on the ischemic colitis-induced region was determined. To assess the colonic damage score and collagen deposition, colonic tissue sections were stained with hematoxylin and eosin (H&E), and Masson trichrome staining was performed. Western blot analysis for A_2AR, vascular endothelial growth factor (VEGF), cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6, Bax, Bcl-2, and extracellular signal-regulated kinase 1/2 (ERK1/2) was performed. Skin temperature was increased and mucosal damage and collagen deposition were observed in the affected colonic tissues in the ischemic colitis rats. Expressions of inflammatory cytokines (TNF-α, IL-1β, and IL-6) and inflammatory mediator (COX-2) were upregulated in the ischemic colitis rats. Apoptosis was increased by decreasing the ratio of Bcl-2 to Bax and by suppressing the phosphorylated form of ERK1/2 expression in the ischemic colitis rats. Treatment with PDRN alleviated mucosal damage reduced the expressions of inflammatory cytokines and COX-2 and inhibited apoptosis in the ischemic colitis rats. PDRN treatment more enhanced the expressions of A_2AR and VEGF in the ischemic colitis rats. PDRN showed therapeutic effectiveness on ischemic colitis by increasing VEGF expression and inhibiting inflammatory cytokines and COX-2 through enhancing A_2AR expression.

Figure 1

Changes in the skin temperature in ischemic colitis-induced region. (■) The sham-operated group, (○) the ischemic colitis-induced group, (△) the ischemic colitis-induced and 4 mg/kg PDRN-treated group, (●) the ischemic colitis-induced and 8 mg/kg PDRN-treated group, and (□) the ischemic colitis-induced and 16 mg/kg PDRN-treated group. ^∗P < 0.05 versus sham-operated group, ^#P < 0.05 versus ischemic colitis-induced group.

Figure 2

Ischemic colitis-induced morphological and histological changes. Left column: morphological analysis. Red arrows indicate hyperemia and ulceration. Middle column: hematoxylin and eosin staining (nuclei were stained blue and fibers were stained pink). Yellow arrows indicate loss of epithelial cells and distortion of mucosa. Right column: Masson trichrome staining (cytoplasm was stained pink and collagen fibers were stained blue). Black arrows indicate collagen deposition. Lower column: morphological score, colonic damage score, and collagen in each group. (A) The sham-operated group, (B) the ischemic colitis-induced group, (C) the ischemic colitis-induced and 4 mg/kg PDRN-treated group, (D) the ischemic colitis-induced and 8 mg/kg PDRN-treated group, and (E) the ischemic colitis-induced and 16 mg/kg PDRN-treated group. Inset shows histological damage and collagen fibers. The scale bar represents 150 μm (A–E). Insets are higher magnification (scale bar: 50 μm). ^∗P < 0.05 versus sham-operated group, ^#P < 0.05 versus ischemic colitis-induced group.

Figure 3

Effects of polydeoxyribonucleotide (PDRN) on the expressions of adenosine A2A receptor (A_2AR) and vascular endothelial growth factor (VEGF) in ischemic colitis-induced tissues. (A) Sham-operated group, (B) ischemic colitis-induced group, (C) ischemic colitis-induced and 4 mg/kg PDRN-treated group, (D) ischemic colitis-induced and 8 mg/kg PDRN-treated group, and (E) ischemic colitis-induced and 16 mg/kg PDRN-treated group. ^∗P < 0.05 versus sham-operated group, ^#P < 0.05 versus ischemic colitis-induced group.

Figure 4

Effects of polydeoxyribonucleotide (PDRN) on the expressions of cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 in ischemic colitis-induced tissues. (A) Sham-operated group, (B) ischemic colitis-induced group, (C) ischemic colitis-induced and 4 mg/kg PDRN-treated group, (D) ischemic colitis-induced and 8 mg/kg PDRN-treated group, and (E) ischemic colitis-induced and 16 mg/kg PDRN-treated group. ^∗P < 0.05 versus sham-operated group, ^#P < 0.05 versus ischemic colitis-induced group.

Figure 5

Effects of polydeoxyribonucleotide (PDRN) on the expressions of Bcl-2, Bax, caspase-3, and extracellular signal-regulated kinase 1/2 (ERK1/2) in ischemic colitis-induced tissues. (A) Sham-operated group, (B) ischemic colitis-induced group, (C) ischemic colitis-induced and 4 mg/kg PDRN-treated group, (D) ischemic colitis-induced and 8 mg/kg PDRN-treated group, and (E) ischemic colitis-induced and 16 mg/kg PDRN-treated group. ^∗P < 0.05 versus sham-operated group, ^#P < 0.05 versus ischemic colitis-induced group.

Figure 6

Effects of polydeoxyribonucleotide (PDRN) and 3,7-dimethyl-1-propargylxanthine (DMPX) on the expressions of adenosine A_2A receptor (A_2AR), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 in ischemic colitis-induced tissues. (A) Sham-operated group, (B) ischemic colitis-induced group, (C) ischemic colitis-induced and 16 mg/kg PDRN-treated group, and (D) ischemic colitis-induced and 16 mg/kg PDRN + 16 mg/kg DMPX-treated group. ^∗P < 0.05 versus sham-operated group, ^#P < 0.05 versus ischemic colitis-induced group.