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Silver nanoparticles (AgNPs) are one of the most widely used nanomaterials. Following oral exposure, AgNPs can accumulate in various organs including kidneys where they show gender specific accumulation. There is limited information on their effect on renal system following long-term animal exposure especially at the ultramicroscopic and molecular level. In this study, we have assessed the effect of 60 days oral AgNPs treatment on kidneys of female Wistar rats at doses of 50 ppm and 200 ppm that are below previously reported lowest observed adverse effect level (LOAEL). AgNPs treatment led to decrease in kidney weight and some loss of renal function as seen by increased levels of serum creatinine and early toxicity markers such as KIM-1, clusterin and osteopontin. We also observed significant mitochondrial damage, loss of brush border membranes, pronounced swelling of podocytes and degeneration of their foot processes using transmission electron microscopy (TEM). These symptoms are similar to those seen in nephrotic syndrome and 'Minimal change disease' of kidney where few changes are visible under light microscopy but significant ultrastructural damage is observed. Prolonged treatment of AgNPs also led to the activation of cell proliferative, survival and proinflammatory factors (Akt/mTOR, JNK/Stat and Erk/NF-κB pathways and IL1β, MIP2, IFN-γ, TNF-α and RANTES) and dysfunction of normal apoptotic pathway. Our study shows how long term AgNPs exposure may promote ultrastructural damage to kidney causing inflammation and expression of cell survival factors. These changes, in the long term, could lead to inhibition of the beneficial apoptotic pathway and promotion of necrotic cell death in kidneys.

Microglia play a dual role in neuroprotection as well as in neurodegeneration and thus occupy the focal interest in neurodegenerative disease research. In vitro studies either by using cell lines or neonatal mouse primary microglia correlated xenobiotic induced microglial activation and neuronal death. However, these in vitro studies cannot portray the in vivo scenario. Therefore, environmental pollutant induced in vivo alteration in microglial function can be best assessed by ex vivo analysis, which is not in use because of limitations in the isolation procedure. Therefore, in the first part of the study we describe an optimized isolation procedure and characterization of isolated cells. The second part of the study demonstrates the utility of the isolated cells in evaluation of immunotoxicological alterations following arsenic, as a model xenobiotic, exposure. Purity of the isolated microglia was checked by immunostaining of microglial (CD11b and CD68) and nonmicroglial (GFAP) markers. Immunostaining of activation marker Iba1 proves that cells were not activated during the isolation procedure. Microglia yield and viability from the treated group shows no significant alterations compared to that of the control group. Proinflammatory cytokines (IL-6 and TNF-α) were upregulated following arsenic treatment as in the case of the LPS stimulated group without alterations in anti-inflammatory IL-10. Phagocytic potential was affected significantly following arsenic exposure without alteration in viability. Thus, our protocol can be proficiently used for quick isolation of primary microglia from adult mouse brain without altering their activation status, and most importantly, the isolated cells can be of aid to the ex vivo evaluation of immunotoxicological alterations.