Prevalence of AgNPs application in medicine as well as industry increased the risk of their accumulation in tissues and organs causing toxic effects on internal organs [51]. Most studies on lung toxicity are conducted by inhalation, but during our oral route experiment, it was found that mice had difficulty in breathing with enlarged lungs size, so the present study evaluated the effect of AgNPs toxicity on lung tissue via monitoring biochemical and histological variations. In general, lung in particular concern is the most vulnerable organ to nanoparticles intoxication post exposure via oral treatment or inhalation.
In the current study, AgNPs intoxication in mice model of both low and high sizes (20 nm and 100 nm) declared lung inflammation as well as genotoxic effects due to accumulation of AgNPs in the lung tissue confirming lung toxicity upon AgNPs intoxication. Furthermore, AgNPs (20 nm) demonstrated more toxic effect than AgNPs (100 nm). Moreover, immunohistochemistry and histopathological alternation was monitored in lung tissue, and oxidative stress besides survivin and MMPs mRNA overexpression.
AgNPs toxic effect was determined according to its physical as well as chemical properties according its size [52]. In previous study, AgNPs ranging from 10–20 nm caused a considerable toxic effect [53]. As Ag + ions are related to the cell death, it is urgent to consider the number of Ag + ions in the inventor suspension of AgNPs [54, 55]. Furthermore, it has been verified that endocytosed AgNPs can be degraded in the lysosomes releasing Ag + ions in the cytosol and further cause cell death.
The oxidative stress has been enhanced by injection of AgNPs (20 nm and 100 nm) in the present study. Where, AgNPs contamination contributed to oxidative stress that resulted in a significant reduction in SOD as well as GST. Previous studies also observed the increment of oxidative stress in the aquatic creatures in the heavy metal contaminated aquatic environment [56]. However, AgNPs supplementation with limited dose (0.5 mg/kg) could improve the obtained oxidative stress; high dose of AgNPs (1mg/kg) increase the oxidative stress validating that AgNPs induce toxicity by the effect of Ag + ions [57].
Herein, the current study deduced the up regulation of survivin mRNA in AgNPs induced lung injury in experimental animals. It was also showed that upon treatment with AgNPs 20 nm treated groups via C. edulis and mucilage improved mRNA gene expression of survivin overexpression. Detection of survivin indicates that it could be considered as an important mediator of cyto-protection, not only in tumor cells but also in lung injured adult cells. Previously, it was confirmed that survivin gene expression was altered in injured lung epithelial cells in both vitro and vivo via activation of caspase-3 and caspase-7 declaring the anti-apoptotic potential of survivin [58]. However, reports observed that survivin could regulate apoptosis and proliferation of both normal cells and cancer cells through similar pathways such as p21-dependent pathways [59]. Continued investigations regarding mechanisms that regulate the expression of survivin and its function in normal and tumor tissues can develop a novel therapeutic strategy [60].
Dysregulation of MMP-9 has been associated with acute lung injury [61]. In the current study, the expression profiles of MMP-9 gene in AgNPs (20nm) intoxicated group of lung tissues were analyzed and declared overexpression of MMP-9 mRNA levels. On the other hand, AgNPs (100 nm) intoxicated group didn’t declare a significant change in MMP-9 expression confirming size dependent genotoxic impact of silver nanoparticle. Our results demonstrated that the expression of MMP-9 was significantly overexpressed in AgNPs (20 nm) intoxicated group as indicated by increased pulmonary inflammation and oxidative stress. This finding suggested that pulmonary overexpression of MMP-9 may be a part of a self-protective response as previously reported by [62, 63].
Ki-67, as a DNA-binding nuclear non-histone protein index is an appealing biomarker of lung cancer where, it was previously reported to be increased in lung cancer patients. Furthermore, it was also previously related to prognosis [64]. However, various investigations recorded an intensive variability in Ki-67 index among diverse individuals that reflect a difference in biological response to other injurious agents [65]. In addition, whereas the increment of Ki-67 index is associated with increasing pre-neoplasia histology, there is an extensive variation in histologic profile, investigating that Ki-67 index could be a promising additional prognostic biomarker in various lung injuries [30]. Different previous studies elucidated that ki-67 could be a prognostic and diagnostic biomarker for lung malfunction [30, 31, 66, 67].
In the present study, sections obtained from AgNPs (100 nm) intoxicated group illustrated nearly 10% of pneumocytes and revealed positive nuclei for ki-67. Whereas, AgNPs (20 nm) intoxicated group demonstrated 40% of pneumocytes showed positive nuclei for ki-67. This results proved the AgNPs (20 nm) has more toxic effect than that induced via AgNPs (100 nm).
Furthermore, the correlation between the expressions of Ki-67 in all studied groups was assessed. The results declared that the expression of Ki-67 is related to the powerful of all used regimen in treatment of injured lung samples. Data recorded indicated an obvious improvement in ki-67 expression in both AgNPs (20 nm) and AgNPs (100 nm) with the superiority of mucilage treated group confirming that ki-67 is an attractive biomarker for lung injury related to AgNPs intoxication.
Treatment of AgNPs intoxicated groups with C. edulis, G.pentaphylla extracts. In addition to mucilage and protein bioactive constituents demonstrated a remarkable improvement in all tested biochemical parameters, apoptotic biomarker, and immunohistochemistry for ki-67 in addition to histopathological examination. The noticeable elaboration is due to the antioxidative properties of these compounds as it increases their health benefits [68]. Herein, this beneficial impact may be due to the existence of active phenolic compounds such as phenolic acids, flavonoids, and phenolic triterpenes tannins [44]. In the present study, G. pentaphylla extracts of stems and leaves showed an obvious antimicrobial as well as antioxidant activities pentaphylla due to the presence of many valuable compounds as phenolics, saponins, alkaloids and tannins. Furthermore, the antioxidant activity of these extracts is associated with high content of flavonoids [69]. Different previous studies were concerned by studying the hepatoprotective effect of vigour of C. edulis and G. pentaphylla [44, 70–72]. Here, we have shed light on the prospective role of the bioactive constituents present in the current extracts against lung toxicity induced via AgNPs. Rosmarinic acid and Garllic acid are phenolic compounds which can protect lung tissues against oxidative stress and pathological alternation for its antioxidant property, its functional property as scavenging reactive oxygen species and their power to improve body antioxidant situation [38]. Different investigations identified more bioactive compounds with antioxidant properties in C. edulis due to the presence of phenolic contents [73].
Additionally, the active constituent Rutin could influence the inhibition of some cancers due to its antioxidant, anti-angiogenic, antiallergic, anti-inflammatory, and antiviral property [74]. Naringenin, dietary flavonoid, improved the physiological alternations caused by isoniazid certain metabolic alteration that declared anti-inflammatory and anti-oxidative properties [75].
In our study, many histopathological changes in the lung tissue of AgNPs intoxicated animal demonstrated alveoli with markedly thick inter-alveolar septum, the septum is infiltrated by large number of lymphocytes and RBCs ruptured alveoli declaring necrosis, and cellular inflammation. These findings are previously recorded by Hassan and Abdelbaky, who reported damage and necrosis in the lung tissue upon AgNPs intoxication [76]. This damage and inflammation is due to the accumulation of silver ions in the lung tissue Furthermore, treatment with C. edulis and G. pentaphylla showed an obvious improvement in lung tissue declaring thin inter-alveolar septum, type I and type II pneumocytes, blood vessel and bronchus. This improvement is due to the considerable antioxidative impact due to the presence of phenolic compounds such as flavonoids in addition to, cytotoxic and antimicrobial activities [44].