Bruno D’Agostino

BACKGROUND: Microplastics and nanoplastics (MNPs) are emerging as a potential risk factor for cardiovascular disease in preclinical studies. Direct evidence that this risk extends to humans is lacking. METHODS: We conducted a prospective, multicenter, observational study involving patients who were undergoing carotid endarterectomy for asymptomatic carotid artery disease. The excised carotid plaque specimens were analyzed for the presence of MNPs with the use of pyrolysis-gas chromatography-mass spectrometry, stable isotope analysis, and electron microscopy. Inflammatory biomarkers were assessed with enzyme-linked immunosorbent assay and immunohistochemical assay. The primary end point was a composite of myocardial infarction, stroke, or death from any cause among patients who had evidence of MNPs in plaque as compared with patients with plaque that showed no evidence of MNPs. RESULTS: A total of 304 patients were enrolled in the study, and 257 completed a mean (±SD) follow-up of 33.7±6.9 months. Polyethylene was detected in carotid artery plaque of 150 patients (58.4%), with a mean level of 21.7±24.5 μg per milligram of plaque; 31 patients (12.1%) also had measurable amounts of polyvinyl chloride, with a mean level of 5.2±2.4 μg per milligram of plaque. Electron microscopy revealed visible, jagged-edged foreign particles among plaque macrophages and scattered in the external debris. Radiographic examination showed that some of these particles included chlorine. Patients in whom MNPs were detected within the atheroma were at higher risk for a primary end-point event than those in whom these substances were not detected (hazard ratio, 4.53; 95% confidence interval, 2.00 to 10.27; P<0.001). CONCLUSIONS: In this study, patients with carotid artery plaque in which MNPs were detected had a higher risk of a composite of myocardial infarction, stroke, or death from any cause at 34 months of follow-up than those in whom MNPs were not detected. (Funded by Programmi di Ricerca Scientifica di Rilevante Interesse Nazionale and others; ClinicalTrials.gov number, NCT05900947.).

Emerging evidence indicates that chemical exposures in the environment are overlooked drivers of cardiovascular diseases (CVD). Recent evidence suggests that micro- and nanoplastic (MNP) particles derived largely from the chemical or mechanical degradation of plastics might represent a novel CVD risk factor. Experimental data in preclinical models suggest that MNPs can foster oxidative stress, platelet aggregation, cell senescence, and inflammatory responses in endothelial and immune cells while promoting a range of cardiovascular and metabolic alterations that can lead to disease and premature death. In humans, MNPs derived from various plastics, including polyethylene and polyvinylchloride, have been detected in atherosclerotic plaques and other cardiovascular tissues, including pericardia, epicardial adipose tissues, pericardial adipose tissues, myocardia, and left atrial appendages. MNPs have measurable levels within thrombi and seem to accumulate preferentially within areas of vascular lesions. Their presence within carotid plaques is associated with subsequent increased incidence of cardiovascular events. To further investigate the possible causal role of MNPs in CVD, future studies should focus on large, prospective cohorts assessing the exposure of individuals to plastic-related pollution, the possible routes of absorption, the existence of a putative safety limit, the correspondence between exposure and accumulation in tissues, the timing between accumulation and CVD development, and the pathophysiological mechanisms instigated by pertinent concentrations of MNPs. Data from such studies would allow the design of preventive, or even therapeutic, strategies. Meanwhile, existing evidence suggests that reducing plastic production and use will produce benefits for the environment and for human health. This goal could be achieved through the UN Global Plastics Treaty that is currently in negotiation.

Sphingosine 1-phosphate (S1P) is a sphingolipid mediator that is involved in diverse biological functions. Local administration of S1P causes inflammation coupled to a large eosinophil (EO) recruitment in the rat-paw tissue. The inflammatory response is accompanied by an increase in S1P receptors, namely S1P(1), S1P(2), S1P(3), and by an enhanced expression of CCR3, which is the main chemokine receptor known to be involved in EO function. Human EOs constitutively express S1P(1) and, at a lower extent, S1P(2), S1P(3) receptors. S1P in vitro causes cultured human EO migration and an increase in S1P receptor mRNA copies and strongly up-regulates CCR3 and RANTES (regulated on activation, normal T cell-expressed and secreted) message levels; in particular CCR3 is up-regulated 18,000-fold by S1P. A blocking anti-CCR3 Ab inhibits S1P-induced chemotaxis, implying that S1P acts as specific recruiting signal for EOs not only through its own receptors but also through CCR3. These results show that S1P is involved in EO chemotaxis and contribute to shed light on the complex mechanisms underlying EO recruitment in several diseases such as asthma and some malignancies.

Sphingosine-1-phosphate (S1P) has been shown to regulate numerous and diverse cell functions, including smooth muscle contraction. Here we assessed the role of S1P/Sphingosine kinase (SPK) pathway in the regulation of bronchial tone. Our objective was to determine, using an integrated pharmacologic and molecular approach, (1) the role of S1P as endogenous modulator of the bronchial tone, and (2) the linkage between S1P pathway and bronchial hyperresponsiveness. We evaluated S1P effects on isolated bronchi and whole lungs, harvested from Balb/c mice sensitized to ovalbumin (OVA) versus vehicle-treated mice, by measuring bronchial reactivity and lung resistance. We found that S1P administration on nonsensitized mouse bronchi does not cause any direct effect on bronchial tone, while a significant increase in Ach-induced contraction occurs after S1P challenge. Conversely, in OVA-sensitized mice S1P/SPK pathway triggers airway hyperesponsiveness. Indeed, S1P causes a dose-dependent contraction of isolated bronchi. Similarly, in the whole lung system S1P increased airway resistance only in OVA-sensitized mice. The action on bronchi of S1P is coupled to an enhanced expression of SPK(1) and SPK(2) as well as of S1P(2) and S1P(3) receptors. In these experiments the key role for S1P/SPK in hyperreactivity has been confirmed by pharmacologic modulation of SPKs. S1P/SPK pathway does not seem to play a major role in physiologic conditions, while it may become critical in pathologic conditions. These results open new windows for therapeutic strategies in diseases like asthma.

Recent studies have revealed that adult stem cells such as bone marrow-derived cells contribute to lung tissue regeneration and protection, and thus administration of exogenous stem/progenitor cells may be a potent next-generation therapy for COPD. Pathogenesis of COPD is characterized by an upregulation of inflammatory processes leading to irreversible events such as apoptosis of epithelial cells, proteolysis of the terminal air-space and lung extracellular matrix components. The available pharmacological treatments are essentially symptomatic, therefore, there is a need to develop more effective therapeutic strategies. It has been previously demonstrated that transplanted MSC home to the lung in response to lung injury and adopt phenotypes of alveolar epithelial cells, endothelial cells, fibroblasts and bronchial epithelial cells. However, engraftment and differentiation are now felt to be rare occurrences and other mechanisms might be involved and play a more important role. Importantly, MSCs protect lung tissue through suppression of proinflammatory cytokines, and through triggering production of reparative growth factors. Accordingly, it is not clear if and how these cells will be able to repair, to slow or to prevent the disease. This article reviews recent advances in regenerative medicine in COPD and highlights that their potential application although promising and very attractive, are still a far away opinion.