IL-13 immunotoxin accelerates resolution of lung pathological changes triggered by silica particles in mice.

Instillation of silica into the lungs of rodents results in pathological changes that strongly mimic human silicosis, an occupational lung disease marked by restrictive airway obstruction, inflammation, and fibrosis. Because IL-13 is a pivotal proinflammatory and fibrogenic cytokine, we examined whether a recombinant immunotoxin comprised of human IL-13 and a mutated form of Pseudomonas exotoxin (IL-13-PE) might affect pathological features of experimental silicosis. Mice received a single intranasal instillation of silica particles and were treated with intranasal IL-13-PE every other day from days 21 to 27 postsilica. The sensitivity of putative cell targets to IL-13-PE was also assessed in in vitro settings. Upregulation of IL-13, its receptor subunits IL-13Rα1 and IL-13Rα2, and shared receptor IL-4Rα were associated with development of granulomatous lung inflammation triggered by silica. IL-13-PE inhibited silica-induced granuloma and fibrotic responses noted at 24 h and 15 d after the last treatment. Upregulation of TNF-α, TGF-ß, and chemokines, as well as increased collagen deposition and airway hyperreactivity to methacholine were all clearly sensitive to IL-13-PE. In addition, IL-13-PE inhibited both IL-13-induced proliferation of cultured lung fibroblasts from silicotic mice and silica-induced IL-8 generation from A549 cells. In conclusion, our findings show that therapeutic treatment with IL-13-PE can reverse important pathological features caused by inhalation of silica particles, suggesting that this recombinant immunotoxin is a promising molecular template in drug discovery for the treatment of silicosis.

A functional IL-13 receptor is expressed on polarized murine CD4+ Th17 cells and IL-13 signaling attenuates Th17 cytokine production.

IL-17A is produced from Th17 cells, and is involved in many autoimmune and inflammatory diseases. IL-13R has not previously been reported to be functionally expressed on T cells; however, we found that purified BALB/c CD4(+) cells polarized to Th17 with TGF-beta, IL-6, and IL-23 have increased mRNA and protein expression of IL-13R alpha1 and mRNA expression of IL-4R alpha compared with Th0, Th1, or Th2 polarized cells. The addition of IL-13 at Th17 polarization negatively regulated IL-17A and IL-21 expression, and reduced the number of CD4(+) T cells producing IL-17A. Further, adding IL-13 at the time of Th17 cell restimulation attenuated IL-17A expression. CD4(+) Th17 polarized cells from IL-4 knockout (KO) mice also had IL-13-induced inhibition of IL-17A production, but this was not observed in IL-4R KO and STAT6 KO mice. Addition of IL-13 at polarization increased IL-13R expression in wild-type Th17 cells. Further, IL-13 administration during Th17 polarization down-regulated retinoic acid-related-gammaT, the transcription required for Th17 development; increased STAT6 phosphorylation, and up-regulated GATA3, the transcription factor activated during the development of Th2 cells. This IL-13-mediated effect was specific to Th17 cells as IL-13 neither decreased IFN-gamma expression by Th1 cells nor affected Th2 cell production of IL-4. Collectively, we have shown that Th17 cells express a functional IL-13R and that IL-13 negatively regulates IL-17A and IL-21 production by decreasing retinoic acid-related-gammaT expression and while increasing phosphorylation of STAT6 and GATA3 expression. Therefore, therapeutic intervention inhibiting IL-13 production could have adverse consequences by up-regulating Th17 inflammation in certain disease states.

IL-13 receptor alpha 2: a regulator of IL-13 and IL-4 signal transduction in primary human fibroblasts.

BACKGROUND: IL-13 and IL-4 share many functional properties as a result of their use of a common receptor complex comprising IL-13 receptor alpha 1 (IL-13Ralpha1) and IL-4 receptor alpha (IL-4Ralpha). The nonsignaling receptor IL-13 receptor alpha 2 (IL-13Ralpha2) binds IL-13 with high affinity and specificity and is believed to be a decoy receptor for IL-13. OBJECTIVE: We sought to examine the inhibitory effects of soluble and membrane-bound IL-13Ralpha2 on IL-13- and IL-4-mediated effects. METHODS: Primary human fibroblasts were grown from endobronchial biopsy specimens obtained from volunteers. Upregulation of IL-13Ralpha2 mRNA was measured by means of RT-PCR, and the level of surface expression was measured by means of FACS. RESULTS: We found that a recombinant soluble form of IL-13Ralpha2 blocked the effects of IL-13, but not IL-4, in fibroblasts in vitro. However, we found that the transmembrane form of IL-13Ralpha2 could attenuate both IL-13 and IL-4 responses, even though the response to TNF-alpha was unaffected. Furthermore, we found that IL-13Ralpha2 became associated with IL-4Ralpha in the presence of IL-4. Addition of a blocking antibody to the extracellular domain of IL-13Ralpha2 restored responses of both IL-13 and IL-4. CONCLUSION: The ability of IL-13Ralpha2 to regulate IL-4 was previously unrecognized in primary airway cells. These data reveal a novel role for IL-13Ralpha2 as a negative regulator of both IL-13 and IL-4 signaling in human bronchial fibroblasts. CLINICAL IMPLICATIONS: It appears that IL-13Ralpha2 might be a powerful suppressor of TH2-mediated responses and thus represents a potential therapeutic target for the treatment of asthma.

[Effects of interleukin 13 on the differentiation and expression of transcription factor c-fos of HEL cells].

OBJECTIVE: To study the effects of IL-13 on the differentiation and expression of transcription factor c-fos of human erythroleukemia cell line (HEL) cells. METHODS: Reverse transcription polymerase chain reaction (RT-PCR) was used to observe the mRNA expression of IL-13 receptor a 1, GP i b, vWF and c-fos, and Western blot and cytometry were used to analyse their protein expression. RESULTS: IL-13 receptor a 1 was expressed on HEL cells. IL-13 (100 ng/ml ) up-regulated the mRNA expression of GP II b and vWF. The ratio of luminous absorption (LA) of GP I b to p-actin bands ( AB) was 1. 303 in control group, whereas was 2. 912 in experiment group; being 2. 23-fold higher than that in control group (P < 0. 05). The ratio of LA to AB for vWF was 0.217 in control group, and 0. 506 in experiment group; indicating a 2. 33-fold increase in experiment group (P <0. 05). The protein expression of GP I b and vWF was significantly increased in experiment group, compared with that in control group. IL-13 inducing the increased expression of c-fos mRNA and protein of HEL cells peaked at 30 min and 60 min, respectively. The ratio of LA to AB for c-fos was also increased at 30 min and 60 min (P <0. 05). CONCLUSION: IL-13 prompts the differentiation of HEL cells and up-regulates the expression of c-fos.