The Role of Recombinant Human Interleukin-8 (CXCL8) in the Pathophysiology of Asthma

Asthma is a chronic inflammatory disease characterized by airway hyperresponsiveness (AHR), inflammation, and remodeling. Recent studies highlight the role of chemokines, particularly Interleukin-8 (CXCL8), in the pathogenesis of asthma. This article investigates the mechanistic pathways through which recombinant human CXCL8 exacerbates asthmatic conditions, focusing on neutrophil recruitment, cytokine release, and airway responsiveness. The findings underscore the potential therapeutic benefits of targeting CXCL8 in asthma management.

Asthma affects millions worldwide and involves complex immunological interactions. Chemokines, including CXCL8, are crucial in mediating the recruitment and activation of inflammatory cells. CXCL8, primarily known for its neutrophil chemotactic properties, has been implicated in the exacerbation of asthmatic symptoms. Elevated levels of CXCL8 in asthmatic patients correlate with disease severity, suggesting its significant role in asthma pathophysiology.

Materials and Methods

Production of Recombinant CXCL8

Recombinant human CXCL8 was produced using an E. coli expression system. The CXCL8 gene was cloned into a pET-28a(+) vector and transformed into E. coli BL21 (DE3) cells. Protein expression was induced with isopropyl β-D-1-thiogalactopyranoside (IPTG), followed by purification using Ni-NTA affinity chromatography. Purity was assessed by SDS-PAGE and Western blotting.

Cell Culture and Treatments

Primary bronchial epithelial cells (PBECs) were isolated from asthmatic and healthy donors and cultured in bronchial epithelial growth medium. Cells were stimulated with pro-inflammatory cytokines (IL-1β, TNF-α) to induce CXCL8 secretion. CXCL8 levels in culture supernatants were measured using ELISA.

Neutrophil Chemotaxis Assays

Neutrophils were isolated from peripheral blood of asthmatic patients and healthy controls using Ficoll-Paque density gradient centrifugation. Chemotaxis assays were performed using transwell chambers. Recombinant CXCL8 (100 ng/mL) was added to the lower chamber, and neutrophil migration was quantified after 2 hours by counting cells that migrated to the lower chamber.

Murine Model of Allergic Asthma

BALB/c mice were sensitized and challenged with ovalbumin (OVA) to induce allergic asthma. Mice received intranasal administrations of recombinant CXCL8 (1 μg/mouse) or vehicle control during the challenge phase. Airway hyperresponsiveness was assessed using a Buxco plethysmograph following methacholine challenge.

Histological and Flow Cytometric Analysis

Lung tissues were fixed, sectioned, and stained with hematoxylin and eosin (H&E) for histological examination. Bronchoalveolar lavage fluid (BALF) was collected, and cellular composition was analyzed by flow cytometry. Multiplex cytokine assays were performed on BALF and serum samples to profile inflammatory mediators.


CXCL8 Expression and Secretion

Stimulation of PBECs with IL-1β and TNF-α significantly increased CXCL8 mRNA and protein levels. Asthmatic PBECs exhibited higher baseline and stimulated CXCL8 secretion compared to controls, indicating a heightened inflammatory state.

Enhanced Neutrophil Chemotaxis

Neutrophils from asthmatic patients displayed increased chemotactic responses to CXCL8 compared to those from healthy donors. The chemotactic index was significantly higher in asthmatic neutrophils, suggesting enhanced sensitivity and recruitment potential.

Airway Hyperresponsiveness:

In the murine model, CXCL8 administration significantly increased AHR, as evidenced by higher Penh values in response to methacholine. This effect was mitigated by pre-treatment with a CXCR1/2 antagonist, confirming the role of CXCL8 in modulating airway responsiveness.

Inflammatory Cell Infiltration

Histological analysis revealed substantial neutrophil and eosinophil infiltration in the lungs of CXCL8-treated mice. Flow cytometry confirmed elevated proportions of these cells in BALF, correlating with increased CXCL8 levels.

Cytokine and Chemokine Profiles

CXCL8-treated mice exhibited elevated Th2 cytokines (IL-4, IL-5, IL-13) and chemokines (CCL11, CCL5) in BALF and serum, indicating an amplified inflammatory response. These findings suggest that CXCL8 not only recruits neutrophils but also enhances the overall inflammatory milieu in asthma.


The study provides comprehensive evidence of CXCL8's role in asthma pathogenesis. Elevated CXCL8 levels in asthmatic airways contribute to neutrophil recruitment, enhanced airway hyperresponsiveness, and a Th2-skewed inflammatory environment. These effects are mediated through CXCR1/2 receptors, highlighting potential therapeutic targets. Blocking CXCL8 signaling could reduce neutrophil-driven inflammation and ameliorate asthma symptoms, providing a novel approach for asthma treatment.

Recombinant human CXCL8 plays a pivotal role in exacerbating asthma by promoting neutrophil chemotaxis, airway hyperresponsiveness, and a pro-inflammatory cytokine milieu. Targeting CXCL8 or its receptors holds promise for innovative therapeutic strategies in managing asthma, particularly in patients with severe, neutrophil-dominated disease.

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