## 8 Translocation of Micro and Nanoplastics to Kidney
[145], but with different kind and size of MPs, time of exposure, and administered doses (Table 3). In accordance with the results of [PERSON] et al. [115], another effect of NPs could be the disruption of processes related to energy metabolism. The authors demonstrated that NPs affect pck1 transcription in kidney by inducing alterations in glucose homeostasis. According to [PERSON] et al. [183], head kidney is one of the most altered sites when fish kidney is exposed to MPs and NPs and head-kidney leucocytes are affected too. [PERSON] et al. [185] found that NPs altered the expression of target genes related to the immune function, cellular stress, and stress-related hormone secretion in _D. labrax_ head kidney. Among these genes _tnfx_ (tumour necrosis factor alpha-like, Gene ID: 100136034), _tgfb_ (transforming growth factor beta 1, Gene ID: 7040), _hsp7_ (heat shock protein 8, Gene ID: 115594641), _mc2r_ (melanocortin 2 receptor, Gene ID: 115567821), and _gr_ (glutathione reductase, Gene ID: 115568704) were interested. With regard to head-kidney leucocytes, [PERSON] et al. [186] found that their phagocytosis and respiratory burst respectively decrease and increase on gilthead seabream (_S. aurata_) and European sea bass (_D. labrax_) after polyvinylchloride (PVC) and polyethylene (PE) microplastics exposure. Moreover, according to the authors, these microplastics induced _nrf2_ (nuclear factor erythroid 2-related factor 2-like, Gene ID: 109102552) up-regulation in seabream HKLs. In addition, [PERSON] et al. [182] tested the expression of stress genes in head kidney. The gene expression of _prdx5_ (peroxiercoxin 5, Gene ID: 115593974) decreased already after 15 days of exposure while the expression of _prdx1_ (peroxiercoflavin 1, Gene ID: 115573364) and _prdx3_ (peroxiercoxin 3, Gene ID: 115596707) increased after 30 days of PVC-MPs. As for other organs (i.g. gills), micro and nanoplastics can exacerbate other compounds toxicity in kidney. For example, [PERSON] et al. [185] found that NPs can amplify humic acid effects. The combination of this compound and nanoplastics induces an alteration of target genes involved in stress-related functions such as ill0 (interleukin 10, Gene ID: 100136835), tgfb, mc2r, and gr gene expression in head kidney of _D. labrax_. Microplastics can affect paraquat effects too [187] and influence blood biochemical parameters in common carp (_C. carpio_). For example, exposure to microplastics was followed by an increase in creatine phosphokinase (CPK) activity in blood that may signify among, other things, renal failure [188]. As reported for gills, [PERSON] et al. [137] found no histological damage to kidneys of zebrafish after microplastics exposure. In the same way, [PERSON] et al. [132] wrote that hematoxylin eosin staining showed no alterations in internal organs (among the others, kidney) of their samples of exposed individuals to MPs. However, all the mentioned studies reported above employed different species, MPs type and sizes, concentrations, and exposure times (see Table 3). This could explain the different effects obtained by the different authors.