The folic acid antimetabolite MTX limits epithelial hyperplasia, reinforces the apoptosis of activated T cells, and inhibits the chemotaxis of neutrophils like anti-inflammatory and immunosuppressive properties (Czarnecka-Operacz and Sadowska-Przytocka 2014, Elango et al. 2014). For these reasons, it is used in some autoimmune diseases such as Crohn's disease, rheumatoid arthritis etc. Besides, MTX inhibits the activity of thymidylate synthase which causes the inhibition of growth and cell death by inhibiting DNA synthesis (Cronstein et al. 1994). It is also used in cancer treatment due the same properties mentioned above.
Among the usage of antineoplastic reason, it leads to causing many organ toxicities by using high doses. Oxidative stress and inflammation play an important role in the background of important side effects such as nephrotoxicity (Howard et al. 2016).
The changes in oxidative stress markers of this study reflected that MTX induces oxidative stress and selected protective agent NBV ameliorated these changes by decreasing ROS levels and increasing antioxidant activities. In preventing this oxidative stress, it may have either prevented the progression of the damage by increasing the number of antioxidant enzymes, or it may have reduced stress indirectly by affecting the mechanisms of inflammation. Akgullu et al. found NBV’s antioxidant properties with the treatment of hyper-homocysteinemia induced kidney injury in rats by decreasing malondialdehyde levels.
Oxidative stress may cause the release of various cytokines that cause inflammation by activating certain intracellular pathways. These released cytokines also affect their cell surface receptors and activate other intracellular pathways and cause the process to become a progressive inflammatory condition (Mahfoudh-Boussaid et al. 2014).
While AKT, which is one of the main intracellular pathways in the progression of this damage, is in contact with many other pathways and may cause aggravation of the damage, it can trigger tissue-protective effects with the NO residue synthesized due to eNOS activation by activating the Hif-1⍺-mediated intermediate pathway.
Hif-1⍺, a transcriptional activator of oxygen homeostasis, is stimulated by several factors like growth factors and NO which coordinate the expression of eNOS enzyme levels to decreased the hypoxic results. So enhancement levels of this gene resulted in vasodilation and decreased the activities of the mentioned damage mechanisms.
As known in the literature, NBV enhances the activity of the eNOS enzyme resulted in vasodilation and improvement of the defense system. For the protection of the kidney against inflammation, Akt/eNOS pathway-related NO synthesis plays a crucial role in cell survival (Mahfoudh-Boussaid et al. 2012). In this study, MTX decreased the activity of AKT1/Hif-1⍺/eNOS signaling and causes positive many histopathological changes. In this model of nephrotoxicity, the effect of NBV on the intracellular AKT pathway was parallel to the literature on eNOS synthesis, and this effect was shown to reduce inflammation in the tissue by histopathological responses. By cytokines, tubular dilatation, epithelial degeneration, hyaline damage and vacuolization in the distal tubule reflected the inflammatory way of MTX on the kidney. NBV treatment ameliorates these findings by using the same pathway and increasing the activity of antioxidant activity. Wang et al. studied on L-NAME –induced hypertension model on rats and they found that NBV treatment enhanced the level of NO synthesized by eNOS to reduce oxidative stress and inflammation (Wang et al. 2017).
Some markers such as BUN and CRE, which are taken from the blood, are used in routine treatment to monitor the degree of these damages in the kidney tissue. In this study enhanced levels of CRE levels by MTX were decreased by NBV reflected that NBV protects the kidney effectively.
Based on all these changes, NBV treatment ameliorated the MTX induced nephrotoxicity via AKT1/Hif-1⍺/eNOS signaling. So, after this stage, serial clinical studies should be conducted in humans, these activities should be proven and should be put into routine use.