Evaluation and comparison of the effects of primary and secondary microplastic on the physiology of the respiratory system of BALB/c mice

• Grant number: 24/17813-9
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: February 01, 2025
• End date: January 31, 2026
• Field of knowledge: Health Sciences - Medicine
• Principal Investigator: Regiani Carvalho de Oliveira
• Grantee: Joao Pedro Albuquerque Damasceno
• Host Institution: Faculdade de Medicina (FM). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Introduction: Plastic is a polymer with characteristics that make its use highly convenient. Consequently, plastic debris is found all over the world and in all ecosystems. Plastics are environmentally persistent, however, once released into the environment, they are exposed to continuous processes such as chemical weathering, photo-oxidation, biological decomposition and mechanical forces, which affect their structural integrity and result in fragmentation at micrometer levels in size, particles between 1um to 5000mm are called microplastics (MP). Human exposure to MP can occur either through ingestion or inhalation. PM has been identified in food intended for human consumption and in air samples collected indoors and outdoors. The proof that PM constitutes a risk to human health is the fact that there is evidence of the presence of PM in human lung tissue and also that it can, via the systemic route, reach other organs, such as the human placenta. Most studies on the toxic effects of PM on the respiratory system use primary particles, which can compromise the accuracy of determining the toxic potential of PM. It has been hypothesized that changes in the shape, composition and size of polymer structures when they are exposed to environmental conditions can alter the toxicity of PM. These secondary particles, while they may lose the compounds added during their production, may adsorb and absorb other compounds during the time they are exposed to the environment. Thus, the toxicological capacity of primary and secondary PM is possibly different. Aim: In the present study we will evaluate the effects of PM particles, naturally degraded polypropylene (PP), secondary PPs (PPs), primary PP particles (PPp), and of the synergistic effect of PP particles with particulate matter from the combustion of DIESEL (DEP) on the respiratory system of male and female BALB/c mice. Methods: Female (N=60) and male (N=60) BALB/c mice will receive daily intranasal instillation for 28 days of 10µL of saline solution containing 300µg of PPs, or 10uL of saline containing 300µg of PPp, or 10uL of saline containing 300µg of PPs and 10ug of DEP, or 10uL of saline containing 300µg of PPp and 10ug of DEP, or 10uL of saline containing and 10ug of DEP, or 10µL of saline solution. The following parameters will be assessed in the mice: inflammatory reaction and cell proliferation indicative of fibrosis and respiratory mucus production in the distal and proximal regions of the mouse lungs, determined by histology; macrophage marker, CD68, and oxidative stress marker, Isoprostane (IsoPs), in the mouse lung fragments, determined by immunohistochemistry.