Consequently, lipid peroxidation causes damage to cell membrane. Oxidative stress induced by nanoparticles is reported to enhance inflammation through

upregulation of redox-sensitive transcription factors including nuclear factor kappa β (NFκβ), activating protein 1 (AP-1), extracellular signal regulated kinases (ERK) c-Jun, N-terminal kinases, JNK, and p38 mitogen-activated protein kinases pathways (Curtis et al., 2006 and Kabanov, 2006). The possible pathophysiological outcomes of effects due to nanomaterials have been concisely complied and presented in selleck chemicals Table 2. Generally speaking, biological systems are able to integrate multiple pathways of injury into a limited number of pathological outcomes, such as inflammation, apoptosis, necrosis, fibrosis, hypertrophy, metaplasia, and carcinogenesis (Table 2). However, even if nanomaterials do not introduce new pathology, there could be novel mechanisms of injury that require special tools, assays, and approaches to assess their toxicity. Specific biological and mechanistic pathways can be elucidated under controlled conditions in vitro; these, in conjunction with in vivo studies would reveal a link of the mechanism of injury to the pathophysiological outcome in the target organ ( Nel et al., 2006). Reactive oxygen species (ROS), due to their

high chemical reactivity can react with DNA, proteins, check details carbohydrates and lipids in a destructive manner causing cell death either by apoptosis or necrosis. The most frequently affected macromolecules are those genes or proteins, which have roles in oxidative stress, DNA damage, inflammation or injury to the immune system. For example, sub-micronic to nanometer-sized preparations of SiO2 were found to increase

arachidonic acid metabolism eventually leading to lung inflammation and pulmonary disease as well as expression in genes directly related to inflammation (Driscoll et al., 1996 and Englen et al., 1990). Similar results were obtained by Ishihara et al. (1999) for nanometer sized TiO2 particles and TiO2 whiskers (width of 140 nm). Based on detailed analyses of studies which investigated the mechanisms of these adverse effects, several researchers Phospholipase D1 have put forth the concept of primary versus secondary genotoxicity (Knaapen et al., 2004, MacNee and Donaldson, 2003 and Vallyathan and Shi, 1997). Genotoxicity directly related to the exposure of the ‘substance’ is referred to as primary genotoxicity. Secondary genotoxicity is the result of the ‘substance’ interacting with cells or tissues and releasing factors, which, in turn, cause adverse effects such as inflammation and oxidative stress. Most investigations on genotoxicity and cellular interactions of engineered nanomaterials are limited to screening for cytotoxicity. A few studies have focused on immunological responses of nanoparticles. Moghimi et al.