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    • In our previous report salivary arginase levels were found t

    2022-11-14

    In our previous report, salivary arginase levels were found to be higher in periodontitis patients compared to healthy controls (Ozmeriç, Elgün, & Uraz, 2000). However, only one study has investigated arginase ezyme in saliva in patients with dental implants in which smokers were also included. An increased salivary arginase enzyme was reported in smoking subjects with dental implants (Queiroz et al., 2009). Our study is the first to report arginase enzyme in saliva and PISF after implant placement, Salivary arginase demonstrated an increasing pattern; however these changes were not found to be statistically significant. PISF arginase levels significantly increased from baseline to months 3 and 6; also, its levels were significantly different from months 1 to 6. The salivary and PISF NO level increases observed in our study might cause to an increase in arginase enzyme. This relationship is best observed in PISF NO levels and arginase activities in months 1, 3, and 6, compared to baseline. In month 1, both values increased. In month 3, again, both values showed an increase, while the levels were the highest in month 6. Since all patients were periodontally healthy, the arginase and NO levels did not correlate with clinical measurements.
    Conclusions
    Conflict of interest
    Acknowledgment
    Introduction Arginase (amidinohydrolase, EC 3.5.3.1) is a ubiquitous enzyme found in various organisms across the living kingdom [1]. This manganese-containing enzyme catalyzes the hydrolysis of l-arginine to l-ornithine and urea (Fig. 1). In mammals, there are two isoenzymes of arginase: arginase I (ARG I, hepatic arginase), a cytosolic enzyme predominantly present in the liver; and arginase II (ARG II, extrahepatic arginase), which is found within the mitochondrial matrix [1]. Arginase has been identified as the final enzyme in the urea g15 and has been implicated in ammonia detoxification in the liver (Fig. 1) [1]. By regulating the availability of l-arginine and l-ornithine, arginase plays an important part in cellular functions of normal and cancer cells. In fact, research over the past decades has reported that high levels of arginase activity have been detected in various types of cancer such as breast [2], pancreatic [3], non-small-cell lung [4] and colorectal [5] cancers. The expression of ARG I in blood-derived myeloid cells of breast cancer patients was significantly reduced after surgical tumor removal [6]. Furthermore, treatment with an arginase inhibitor inhibited the proliferation and induced the apoptosis of high-arginase-expressing cancer cells [2]. Recently, Secondini et al. reported that arginase inhibition could suppress lung metastasis in the 4T1 breast cancer model and this effect was independent of the immunomodulatory and antimetastatic effects of vascular endothelial growth factor receptor (VEGFR)-2 blockade [7]. Taken altogether, the experimental evidence has suggested that arginase might be an attractive target for cancer therapy and diagnostics. In the following sections, we outline the main roles of arginase in development of cancer through three relevant pathways: arginase/polyamine, arginase/nitric oxide synthase (NOS) and arginase/immune responses. Next, the potential for arginase inhibition in cancer therapy will be reported, and then the principal categories of arginase inhibitors derived from synthesis and natural products as well as their mechanisms-of-action will be reviewed. Finally, some perspectives of arginase inhibitors in cancer treatment will be given.
    Roles of arginase in cancer
    Research of arginase inhibitors From the discovery of arginase in mammals, the knowledge on this enzyme and its role in disease pathophysiology has been growing non-stop [1]. Upregulation of the arginase pathway has been reported to be involved in various diseases including cardiovascular diseases [18], nervous system diseases and cancer [22], making arginase a promising therapeutic target in many diseases [1]. Since the 1990s, the structure of arginase and its catalytic mechanism have been explored using X-ray crystallography [32]. Many research projects have been conducted to discover potent and selective arginase inhibitors (for more detail, see the review by Pudlo et al.[33]). Nowadays, new arginase inhibitors could be figured out by combining in silico studies and experimental models [34].