Anti‐inflammatory effects of the R2 peptide, an inhibitor of transglutaminase 2, in a mouse model of allergic asthma, induced by ovalbumin

Abstract

BACKGROUND AND PURPOSETransglutaminase 2 (TGase 2) expression is increased in inflammatory diseases, and TGase 2 inhibitors block these increases. We examined whether the R2 peptide inhibited the expression of TGase 2 in a mouse model of inflammatory allergic asthma. EXPERIMENTAL APPROACHC57BL/6 mice were sensitized and challenged by ovalbumin (OVA) to induce asthma. OVA-specific serum IgE and leukotrienes (LTs) levels were measured by enzyme-linked immunosorbent assay. Recruitment of inflammatory cells into bronchoalveolar lavage (BAL) fluid or lung tissues and goblet cell hyperplasia were assessed histologically. Airway hyperresponsiveness was determined in a barometric plethysmographic chamber. Expression of TGase 2, eosinophil major basic protein (EMBP), the adhesion molecule vascular cell adhesion molecule-1, Muc5ac and phospholipase A2 (PLA2) protein were determined by Western blot. Expression of mRNAs of Muc5ac, cytokines, matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) were measured by reverse transcriptase-polymerase chain reaction and nuclear factor-kB (NF-kB) by electrophoretic mobility shift assay. KEY RESULTSR2 peptide reduced OVA-specific IgE levels; the number of total inflammatory cells, macrophages, neutrophils, lymphocytes and eosinophils in BAL fluid and the number of goblet cells. Airway hyperresponsiveness, TGase 2 and EMBP levels, mRNA levels of interleukin (IL)-4, IL-5, IL-6, IL-8, IL-13, RANTES, tumour necrosis factor-a, and MMP2/9, Muc5ac, NF-kB activity, PLA2 activity and expressions, and LT levels in BAL cells and lung tissues were all reduced by R2 peptide. R2 peptide also restored expression of TIMP1/2. CONCLUSION AND IMPLICATIONSR2 peptide reduced allergic responses by regulating NF-kB/TGase 2 activity in a mouse model of allergic asthma. This peptide may be useful in the treatment of allergic asthma. AbbreviationsBAL, bronchoalveolar lavage; ELISA, enzyme-linked immunosorbent assay; EMBP, eosinophil major basic protein; EMSA, electrophoretic mobility shift assay; MMP, matrix metalloproteinase; NF-kB, nuclear factor-kappa B; OVA, ovalbumin; PAS, periodic acid-Schiff; PBS, phosphate buffered saline; PLA2, phospholipase A2; RT-PCR, reverse transcriptase-polymerase chain reaction; TGase 2, transglutaminase 2; TIMP, tissue inhibitor of matrix metalloproteinase BJP British Journal of Pharmacology

Inhibition of allergic inflammation by supplementation with 5-hydroxytryptophan

“…In the mouse, daily intraperitoneal administration of a TG2 peptide inhibitor (KVLDGQDP) is reported to block OVA-induced lung inflammation (64,65). In these studies, the cellular targets of the TG peptide inhibitor are not known.…”

“…A TG2 peptide inhibitor (KVLDGQDP) administered by daily intraperitoneal injection is reported to block OVA-induced lung expression of TG2, VCAM-1, IL-4, IL-5, and IL-13 (64,65). In contrast to these studies with a peptide and unknown cellular targets of the peptide, we report that supplementation with 5-HTP did not alter OVA-induced lung tissue mRNA expression of adhesion molecules, cytokines, chemokines, or chemokine receptors, including lung tissue expression for the Th2 cell cytokines IL-4 and IL-5.…”

Regulation and Function of Epithelial Secreted Phospholipase A2 Group X in Asthma

“…Further activation of the mature sPLA 2 -X protein may also be important in asthma, as we previously found that transglutaminase 2 is overexpressed in the airways of patients with asthma and increases the enzymatic activity of human sPLA 2 -X (38). A dual inhibitor of transglutaminase 2 and sPLA 2 in the lipocortin family inhibited the development of inflammation and AHR in a murine model of asthma (39). Although the expression of PLA2G10 was much higher in epithelial cells than other airway cells, it is possible that the elevated level of sPLA 2 -X is due to secretion of the protein from a nonepithelial source.…”

Transglutaminase II/MicroRNA-218/-181a Loop Regulates Positive Feedback Relationship between Allergic Inflammation and Tumor Metastasis

“…TGaseII expressed in mast cells enhances IgE level in B cells by regulating CD40L (14). R2 peptide, an inhibitor of TGaseII, reduces * This work was supported by National Research Foundation Grants allergic responses by regulating NF-B/TGaseII activity in a mouse model of allergic asthma (15). Octapeptide R2 (KVLDGQDP), which has anti-transglutaminase (TGase) activity, decreases inflammation in an allergic conjunctivitis model in guinea pigs (16).…”