A new therapeutic approach using a schizophyllan-based drug delivery system for inflammatory bowel disease

Abstract

Antisense technologies for the targeted inhibition of gene expression could provide an effective strategy for the suppression of inflammation. However, the effective use of antisense oligonucleotides (ODN) has been limited because of several problems. Therefore, a delivery system for antisense ODNs that enhances antisense stability, while maintaining the specificity of antisense for its target RNA or DNA is needed. We have developed a delivery system for antisense ODN using schizophyllan (SPG), a polysaccharide that belongs to the β-(1-3) glucan family. This system has several advantages enabling the effective suppression of targeted RNA or DNA: the SPG complex is stable in vivo and does not dissolve in the presence of deoxyribonuclease, and the SPG complex is effectively taken up into macrophages by phagocytosis through Dectin-1. Macrophage-migration inhibitory factor (MIF), which is mainly produced by macrophages has been shown to have a pathogenetic role in inflammatory bowel disease (IBD). We developed a technique to create an SPG complex that highly conformed to the antisense MIF. The administration of antisense MIF/SPG complex effectively suppressed MIF production and significantly ameliorated intestinal inflammation. Our result demonstrated a possible new therapeutic approach, i.e., the administration of antisense MIF/SPG complex, for the treatment of IBD.

Figure 1

Schematic illustration showing a complex structure composed of an oligonucleotide (ODN) with a dA tail and schizophyllan (SPG) as well as antisense migration inhibitory factor (MIF)/SPG complex. (a) Chemical structure of SPG. (b) Schematic illustration of SPG–ODN complex. (c) A triple-stranded complex is formed from one DNA and two SPG strands with interactions between the two SPG main-chain glucoses and one dA.

Figure 2

Synthesis of schizophyllan (SPG)-antisense migration inhibitory factor (MIF) complex was confirmed using GPC and PAGE. (a) Gel-permeation chromatograms of antisense MIF with a (dA)₄₀ tail (red) and its mixture with SPG (blue). The eluant was measured at a UV absorbance of 260 nm. (b) PAGE patterns for the antisense MIF (naked) and its mixture with SPG (mixture).

Figure 3

Migration inhibitory factor (MIF) expression is upregulated in mesenteric lymph node (MLN) and lamina propria (LP) in dextran sodium sulfate (DSS)-induced colitis. (a) Serum MIF concentration, as measured using an enzyme-linked immunosorbent assay (ELISA) (n = 5 per group). (b) Interleukin (IL)-1β, IL-6, and MIF mRNA expression was determined in MLN and colon specimens using real-time PCR (n = 5 per group). Data were normalized to the expression of β-actin mRNA. (c) Immunohistological staining for MIF in colonic tissue from DSS-treated mice and untreated mice. (d) CD11b⁺ cells were isolated from LP and MLN in the DSS-treated mice and untreated mice. CD11b⁺ cells were cultured with 1 µg/ml of LPS. MIF expression was measured at the indicated time point (0, 1, 4, 8, 16, 24, and 48 hours) using real-time PCR and ELISA. The cytokine mRNA expressions were determined in colon and MLN specimens using real-time PCR. Data were normalized to the expression of β-actin mRNA. (e) The supernatants were collected, and the cytokine productions were measured using an ELISA.

Figure 4

Dectin-1 for the receptor of schizophyllan (SPG) was increased in dextran sodium sulfate (DSS) induced acute colitis. (a) Dectin-1 mRNA expression was determined in the mesenteric lymph node (MLN) and colon using real-time PCR. The data were normalized to the expression of β-actin mRNA. (b) Dectin-1 and CD11b expression in the lamina propria (LP) and MLN were analyzed using fluorescence-activated cell sorting (FACS). The data were presented as the mean of three independent experiments.

Figure 5

Antisense migration inhibitory factor (MIF)/schizophyllan (SPG) complex inhibited MIF production induced by LPS in vitro. (a) CD11b⁺ cells from lamina propria (LP) and mesenteric lymph node (MLN) were cultured with several concentrations of antisense MIF/SPG complex (ASMIF), scramble control DNA/SPG complex (SCMIF), and SPG as a control. After 10 hours, 1 µg/ml of LPS was added under each condition and the cells were cultured for 24 hours. MIF expressions were measured using an enzyme-linked immunosorbent assay (ELISA) (n = 5 per group). The data presented are the means of the cytokine concentration ± SD. (b) Immunofluorescence in CD11b⁺ cells was performed by labeling antisense MIF with TAMRA and the SPG with fluorescein isothiocyanate (FITC). CD11b⁺ cells took up the antisense MIF/SPG complex effectively compared with the antisense MIF alone. (c) Neutralizing anti-Dectin-1 antibodies inhibited the uptake of FITC-labeled antisense MIF/SPG complex into CD11b⁺ cells compared with rat IgG2b. The data were presented as the mean of three independent experiments.

Figure 6

Attenuation of dextran sodium sulfate (DSS)-induced colitis by the administration of antisense migration inhibitory factor (MIF)/schizophyllan (SPG) complex. A total of 0.2 mg/kg of antisense MIF/SPG complex (ASMIF), scramble control DNA/SPG complex (SCMIF), SPG, or PBS as a control were injected intraperitoneally (i.p.) twice weekly into mice receiving DSS (n = 8 per group). (a) Body weights as a percentage of the initial weight on day 0 are shown. (b) Colon length from the terminal ileum to the rectum. (c) Endoscopic findings for the colon. (d) Hematoxylin and eosin (H&E) staining of the colon (original magnification: ×100). (e) The histological scores were evaluated.

Figure 7

Administration of antisense migration inhibitory factor (MIF)/schizophyllan (SPG) complex suppressed cytokines in dextran sodium sulfate (DSS)-induced colitis. (a) The serum MIF concentration was measured using an enzyme-linked immunosorbent assay (ELISA) (n = 5 per group). (b) IL-1β, IL-6 and MIF mRNA expression were determined in the MLN and colon using real-time PCR (n = 5 per group). Data were normalized to the expression of β-actin mRNA.