Tim4, a macrophage receptor for apoptotic cells, binds polystyrene microplastics via aromatic-aromatic interactions.

Understanding the interface between microplastics and biological systems will provide new insights into the impacts of microplastics on living organisms. When microplastics enter the body, they are engulfed preferentially by phagocytes such as macrophages. However, it is not fully understood how phagocytes recognize microplastics and how microplastics impact phagocyte functions. In this study, we demonstrate that T cell immunoglobulin mucin 4 (Tim4), a macrophage receptor for phosphatidylserine (PtdSer) on apoptotic cells, binds polystyrene (PS) microparticles as well as multi-walled carbon nanotubes (MWCNTs) through the extracellular aromatic cluster, revealing a novel interface between microplastics and biological systems via aromatic-aromatic interactions. Genetic deletion of Tim4 demonstrated that Tim4 is involved in macrophage engulfment of PS microplastics as well as of MWCNTs. While Tim4-mediated engulfment of MWCNTs causes NLRP3-dependent IL-1ß secretion, that of PS microparticles does not. PS microparticles neither induce TNF-α, reactive oxygen species, nor nitric oxide production. These data indicate that PS microparticles are not inflammatory. The PtdSer-binding site of Tim4 contains an aromatic cluster that binds PS, and Tim4-mediated macrophage engulfment of apoptotic cells, a process called efferocytosis, was competitively blocked by PS microparticles. These data suggest that PS microplastics do not directly cause acute inflammation but perturb efferocytosis, raising concerns that chronic exposure to large amounts of PS microplastics may cause chronic inflammation leading to autoimmune diseases.

Severe complication subsequent to surgical site infection after cervical laminoplasty: a case report.

INTRODUCTION: Surgical site infections (SSI) following spinal surgery can result in serious complications. Although early detection and intensive care are essential to minimize possible sequelae, more than one surgical intervention is required to alleviate the infection in some cases. CASE PRESENTATION: A 66-year-old man with long-standing Parkinson's disease (PD) developed SSIs after cervical laminoplasty. Despite surgical debridement and irrigation, his neurological status worsened severely and anterior infectious involvement at the C4-5 level was identified by magnetic resonance imaging. He underwent another urgent surgery for anterior debridement and iliac bone grafting. His laboratory results gradually normalized with antibiotic therapy, and his neurological status improved. One year after surgery, he was ambulatory with walker assistance. However, his right hand remained difficult to control with significant sensory loss and numbness. DISCUSSION: To our knowledge, this is the first case of SSI that extended rapidly to the anterior side despite immediate and intensive treatment in a patient with PD after laminoplasty. During SSI treatment, meticulous observation should be performed to check for exacerbations.