The role of protein tyrosine phosphatases in the regulation of allergic asthma: implication of TC-PTP and PTP-1B in the modulation of disease development

Abstract

Protein tyrosine phosphorylation is an important early event in the signal transduction of numerous cell receptors involved in the immune response. The implication of protein tyrosine kinases in allergic asthma is well recognized, but the role of protein tyrosine phosphatases (PTPs) remains poorly understood. However, we recently reported that global inhibition of PTPs during either the allergen-sensitization phase or the allergen-challenge phase reduced the development of asthma and that this correlated with an increased T helper 1 (Th1) response in both lung and spleen tissues. Therefore, in this study we investigated individual roles of PTPs involved in regulating the immune response. We observed that genetic deficiency for PTP-1B resulted in increased recruitment of lung inflammatory cells, while protein tyrosine phosphatase-phosphatase and tensin homologue deleted (PTP-PEST)-deficient mice exhibited a phenotype similar to that of wild-type mice. Importantly, we found that a heterozygous mutation of T cell PTP (TC-PTP) dramatically abrogates immunoglobulin E production and reduces the recruitment of inflammatory cells to the lung, conferring an important role for TC-PTP in the development of allergic asthma. As opposed to other studies on Src homology phosphatase-1 (SHP-1) deficiency, specific acute SHP-1 inhibition during allergen challenge did not affect disease outcome. Collectively, our results underscore the importance of PTPs in the development of allergic asthma.

Figure 1

Serum immunoglobulin E (IgE) levels. Blood was collected after the mice were killed and the serum was obtained. (a) Total serum IgE levels and (b) ovalbumin-specific serum IgE levels were measured using sandwich enzyme-linked immunosorbent assays (ELISAs). Inhibition of Src homology phosphatase-1 (SHP-1) activity was performed at allergen challenge, not at allergen sensitization. Data shown represent the average of 15–16 [protein tyrosine phosphatase-1B (PTP-1B)], 7–8 protein tyrosine phosphatase-phosphatase and tensin homologue deleted (PTP-PEST), 9–12 T cell PTP (TC-PTP) and 3–4 (SHP-1) animals per group. *Significant difference compared with the appropriate control or identified sample (P ≤ 0.05). A, absorbance; adenovirus (Adv); controls (Ctrls); GFP, green fluorescent protein; KO, knockout; OVA, ovalbumin; WT, wild type.

Figure 2

Inflammatory cells of the bronchoalveolar lavage fluid (BALF). The recruitment of inflammatory cells to the BALF compartment was evaluated using differential counts and total cell counts. Total cell counts (a), lymphocyte counts (b) and eosinophil counts (c) are presented. Data shown represent the average of 11–14 [protein tyrosine phosphatase-1B (PTP-1B)], 5–7 protein tyrosine phosphatase-phosphatase and tensin homologue deleted (PTP-PEST), 5–10 T cell PTP (TC-PTP) and 8 Src homology phosphatase-1 (SHP-1) animals per group. *Significant difference compared with the appropriate control or identified sample (P ≤ 0.05). adenovirus (Adv); controls (Ctrls); GFP, green fluorescent protein; KO, knockout; OVA, ovalbumin; WT, wild type.

Figure 3

Lung tissue inflammatory cells. Local tissue inflammation was evaluated on histology cuts, of 5-μm thickness, stained with haematoxylin and eosin. Observations were made at 400× magnification on 7–9 [protein tyrosine phosphatase-1B (PTP-1B)], 4 protein tyrosine phosphatase-phosphatase and tensin homologue deleted (PTP-PEST), 4–7 T cell PTP (TC-PTP) and 4 Src homology phosphatase-1 (SHP-1) animals per group. *Significant difference compared with the appropriate control or identified sample (P ≤ 0.05). adenovirus (Adv); controls (Ctrls); KO, knockout; OVA, ovalbumin; WT, wild type.

Figure 4

Inhibition of Src homology phosphatase-1 (SHP-1) activity and lung reactivity. (a) Following intravenous injection of the adenovirus expressing a short hairpins RNAs (shRNAs) to SHP-1, inhibition of SHP-1 protein expression was investigated in the spleen on days 3, 5 and 7. The injection of the control green fluorescent protein (GFP)-expressing adenovirus did not affect the expression of (SHP-1) (data not shown). Data shown are representative of three individual experiments. (b) The lung reactivity was evaluated using the Enhanced pause (Penh) measure. Administration of the adenovirus was performed 3 days before allergen challenge to ensure inhibition of SHP-1. Data shown represent the average of 8 animals per group. *Significant difference with appropriate control or identified sample (P ≤ 0.05). SAL, saline.