Impacts of foodborne inorganic nanoparticles on the gut microbiota-immune axis: potential consequences for host health

Abstract

Background: In food toxicology, there is growing interest in studying the impacts of foodborne nanoparticles (NPs, originating from food additives, food supplements or food packaging) on the intestinal microbiome due to the important and complex physiological roles of these microbial communities in host health. Biocidal activities, as described over recent years for most inorganic and metal NPs, could favour chronic changes in the composition and/or metabolic activities of commensal bacteria (namely, intestinal dysbiosis) with consequences on immune functions. Reciprocally, direct interactions of NPs with the immune system (e.g., inflammatory responses, adjuvant or immunosuppressive properties) may in turn have effects on the gut microbiota. Many chronic diseases in humans are associated with alterations along the microbiota-immune system axis, such as inflammatory bowel diseases (IBD) (Crohn's disease and ulcerative colitis), metabolic disorders (e.g., obesity) or colorectal cancer (CRC). This raises the question of whether chronic dietary exposure to inorganic NPs may be viewed as a risk factor facilitating disease onset and/or progression. Deciphering the variety of effects along the microbiota-immune axis may aid the understanding of how daily exposure to inorganic NPs through various foodstuffs may potentially disturb the intricate dialogue between gut commensals and immunity, hence increasing the vulnerability of the host. In animal studies, dose levels and durations of oral treatment are key factors for mimicking exposure conditions to which humans are or may be exposed through the diet on a daily basis, and are needed for hazard identification and risk assessment of foodborne NPs. This review summarizes relevant studies to support the development of predictive toxicological models that account for the gut microbiota-immune axis.

Basal Ti level in the human placenta and meconium and evidence of a materno-foetal transfer of food-grade TiO2 nanoparticles in an ex vivo placental perfusion model

“…A large variety of effects on developmental processes have been reported for TiO 2 -NPs, particularly on brain functions due to translocation through the foetal blood–brain barrier, with consequences on behaviour [ 22 ] . In addition, because immunotoxic and antibacterial properties have been reported for TiO 2 (nano) particles, including the food-grade form [ 7 , 60 – 63 ], their accumulation in the foetal gut through the meconium, as shown herein, could affect the primary colonization of the intestine by the microbiota at birth as well as the maturation of the intestinal immune system, two perinatal events of which dysfunctions have long-term health consequences, as recently reviewed [ 64 ]. Accumulation in the placenta may also lead to placental dysfunction (e.g., dysregulation of vascularization, inhibition of cell proliferation, induction of apoptosis) and subsequent foetal growth restriction [ 11 ].…”

Developmental Exposure to Silver Nanoparticles Leads to Long Term Gut Dysbiosis and Neurobehavioral Alterations

“…The reductions in microglial cells could also be due to effects of developmental exposure to silver NPs as shown in other studies that examined direct effects in adult rodent models. 112…”

Probiotics Supplements Reduce ER Stress and Gut Inflammation Associated With Gliadin Intake in Celiac Disease Mouse Model

“…The GI tract is also a complex ecosystem in which the microbiota has been recently described as an 'extra organ' of the body. It is mainly constituted of bacteria, as well as archaea, viruses, protozoa and fungi [39]. Adult human gastrointestinal tract harbors about trillions of bacteria, including at least several hundred species and more than 6000 strains.…”

“…However, this is not an isolated ecosystem but, on the contrary, it is intensely and actively connected with the host, via a bidirectional intense communication. Indeed, it plays key roles in GI functions such as: microbes facilitate the digestion and transformation of indigestible polysaccharides, provide vitamins, participate to the shaping of the intestinal epithelium, are involved in host immune defense against pathogens in the intestinal lumen, and contribute to the maintenance of intestinal homeostasis [39]. Although the community of the GI microbiota does not undergo significant fluctuations throughout adult life, antibiotic exposure, infections, lifestyle, and diet might profoundly affect it.…”