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

Deiweson Souza-Monteiro,Manoela Domingues Martins,Felipe Martins Silveira,Aline Dionizio,Márcia Cristina Dos Santos Guerra,Maria Elena Crespo-Lopez,Rafael Rodrigues Lima,Marília Afonso Rebelo Buzalaf,Leonardo Oliveira Bittencourt,Walessa Alana Bragança Aragão

doi:10.3390/ijms23042251

Abstract

Aluminum (Al) is one of the most abundant elements on Earth, and its high extraction rate and industrial use make human exposure very common. As Al may be a human toxicant, it is important to investigate the effects of Al exposure, mainly at low doses and for prolonged periods, by simulating human exposure. This work aimed to study the effects of low-dose exposure to chloride aluminum (AlCl3) on the oxidative biochemistry, proteomic profile, and morphology of the major salivary glands. Wistar male rats were exposed to 8.3 mg/kg/day of AlCl3 via intragastric gavage for 60 days. Then, the parotid and submandibular glands were subjected to biochemical assays, proteomic evaluation, and histological analysis. Al caused oxidative imbalance in both salivary glands. Dysregulation of protein expression, mainly of those related to cytoarchitecture, energy metabolism and glandular function, was detected in both salivary glands. Al also promoted histological alterations, such as acinar atrophy and an increase in parenchymal tissue. Prolonged exposure to Al, even at low doses, was able to modulate molecular alterations associated with morphological impairments in the salivary glands of rats. From this perspective, prolonged Al exposure may be a risk to exposed populations and their oral health.

Highlights

Aluminum (Al) is an element that is widely distributed in the Earth’s crust and is of great environmental importance because of its excellent physical properties; it is used by industries at large scales [1]
Our study evaluated the possibility of oxidative imbalance and its association with the modulation of the proteomic profile and impairments in the morphology of the two main pairs of major salivary glands after chronic Al exposure
Our results show that exposure to Al reduced the antioxidant capacity against peroxyl radicals (ACAP) in the parotid glands (aluminum chloride (AlCl3): 57.79 ± 5.73%; control: 100 ± 8.99%, p = 0.0019) and in the submandibular glands (AlCl3: 36.9 ± 7.94%; control: 100 ± 8.17%, p = 0.0001) (Figure 1A)

Summary

Introduction

Aluminum (Al) is an element that is widely distributed in the Earth’s crust and is of great environmental importance because of its excellent physical properties; it is used by industries at large scales [1]. The presence of residual Al in drinking water is one of the most common forms of exposure to the metal [7] and studies indicate that Al can enter the human body through a combination of Al ions with other molecules, forming aluminum salts that can be absorbed in the stomach [8,9]. 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]

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