Oral subacute polypropylene microplastics administration effect on potential immunotoxicity in ICR mice

Area of Science:

• Environmental Science
• Immunology
• Toxicology

Background:

• Microplastic exposure is a growing concern for environmental and human health.
• Polypropylene microplastics (PP-MPs) have widespread applications but their impact on the immune system is not well understood.
• Investigating the immunotoxicity of PP-MPs is crucial for risk assessment.

Purpose of the Study:

• To evaluate the effects of two different sizes of PP-MPs on immune system components in mice.
• To assess potential sex-specific differences in immune responses to PP-MPs.
• To determine the dose-dependent and duration-dependent toxicity of PP-MPs on immune function.

Main Methods:

• Oral administration of PP-MPs (5.2 and 23.9 μm) to ICR mice (female and male) at varying doses (500, 1000, 2000 mg/kg/d).
• Single and 4-week repeated toxicity tests were conducted.
• Analysis of immune cell populations (T lymphocytes, B cells) and cytokine production (IFN-γ, IL-4, TNF-α) from activated splenocytes ex vivo.
• Measurement of serum immunoglobulin ratios (IgG2a/IgG1).

Main Results:

• No significant changes in the counts of thymic T lymphocytes (CD4+, CD8+, CD4+CD8+) or splenic lymphocytes (helper T cells, cytotoxic T cells, B cells).
• Repeated PP-MP administration lowered the IFN-γ/IL-4 ratio in female mice, indicating a shift towards type-2 helper T cell responses, while males showed the opposite trend.
• Tumor necrosis factor-α production was upregulated in females exposed to PP-MPs.
• The serum IgG2a/IgG1 ratio decreased in females receiving large-sized PP-MPs.

Conclusions:

• Repeated exposure to PP-MPs may induce immune disturbances, characterized by a predominant type-2 helper T cell reactivity, especially in female mice.
• The size and dose of PP-MPs might influence the observed immunomodulatory effects.
• Longer exposure studies are necessary to fully elucidate the immunotoxic potential of PP-MPs.