Chronic exposure to inorganic mercury induces biochemical and morphological changes in the salivary glands of rats

Abstract

Mercury exposure is considered to be a public health problem due to the generation of toxic effects on human health as a result of environmental and occupational conditions. The inorganic form of mercury (HgCl) can cause several biological changes in cells and tissues through its cumulative toxic potential, but little has been experimentally proven about the effects of inorganic mercury on salivary glands, an important modulator organ of oral health. This study analyzes the effects of prolonged low dose exposure to HgCl on the salivary glands of rats. Adult animals received a dose of 0.375 mg kg day over a period of 45 days. The parotid and submandibular glands were collected for analysis of the mercury levels and evaluation of oxidative stress, histological parameters and immunomodulation for metallothionein I and II (MT-I/II). In this investigation, biochemical and tissue changes in the salivary glands were verified due to the mercury levels, causing reduction in antioxidant capacity against peroxyl radicals, with consequent cellular lipid peroxidation and an increase in nitrite levels, volumetric changes and cytoskeletal damage in the submandibular glands, with less severe damage to the parotid glands. The results also have shown the occurrence of a cytoprotection mechanism due to increased MT-I/II expression, but not enough to avoid the morphology and oxidative damage. This evidence highlights, for the first time, that inorganic mercury is able to alter the morphology and oxidative biochemistry in salivary glands when exposed for a long time in low doses.

Salivary Glands after Prolonged Aluminum Exposure: Proteomic Approach Underlying Biochemical and Morphological Impairments in Rats

“…Previous reports have shown that major salivary glands are susceptible to metalinduced toxicity in models of exposure to lead [21], inorganic mercury [16], and methylmercury [17][18][19]. The last model also induces several proteomic damages, in the parotid and submandibular glands, especially changes in proteins related to cytoskeleton and energy metabolism pathways [17].…”

“…Our group has performed several studies regarding the effects of metals on the salivary glands in animal models, showing that those elements are capable of trigger tissue and redox impairments that affect the animals' stomatognathic system [16][17][18][19][20][21][22]. Other studies have also revealed damage to those organs after Al exposure [27,28], but to the best of our knowledge, this is the first study that used a proteomic approach to investigate the effects of exposure to a translational dose of Al over salivary glands.…”

“…Malfunction of the salivary glands can interfere with oral homeostasis by altering the quality and quantity of saliva, which can cause or aggravate several disorders, such as xerostomia and periodontal disease [14,15]. Studies from our group have already shown that salivary glands are susceptible to injury caused by exposure to metals, such as mercury, lead, and even Al [16][17][18][19][20][21][22].…”

From Molecules to Behavior in Long-Term Inorganic Mercury Intoxication: Unraveling Proteomic Features in Cerebellar Neurodegeneration of Rats

“…Although inorganic species have unfavorable physical-chemical characteristics to biomagnify and bioaccumulate, the presence of IHg in contaminated fish commercially available and consumed by humans was already evidenced [ 6 ]. In the past few years, our group has shown that several other organs are susceptible to IHg toxicity, such as blood [ 16 ], salivary glands [ 23 ], and the central nervous structures such as the hippocampus, motor cortex, and spinal cord [ 17 , 18 , 19 , 20 , 21 ] after the exposure to 0.375 mg/kg per day of HgCl 2 . Then, despite all the toxicokinetic features, the long-term exposure to IHg increased the levels of total mercury in cerebellar parenchyma of adult rats about 4-fold higher than non-exposed animals significantly.…”

Methylmercury exposure during prenatal and postnatal neurodevelopment promotes oxidative stress associated with motor and cognitive damages in rats: an environmental-experimental toxicology study

“…Each sample of hippocampus and cerebellum were weighted (weighting 0.5 g maximum), which consists in wet digestion of samples through homogenizing a wet sample; further, 1 mL of distilled water, 2 mL of nitric acid-perchloric acid 1:1 (v:v) (HNO 3 -HClO 4 ), and 5 mL of sulfuric acid (H 2 SO 4 ) were sequentially added, which were maintained on a heat plate (200–230 °C) for 30 min. All procedures were based on protocol, following previously published studies by our research group [21] , [22] , [32] , [33] , [43] , with a limit of detection of values until 0.001 mg/kg Hg. The results were expressed in mg/kg of total Hg levels.…”