In dogs, periodontal disease (PD) is a highly common condition whose prevalence rises significantly with age. Studies on rats with experimentally induced PD and human clinical trials have found an association between oxidative stress (OS) and PD, as has been observed in many other inflammatory disorders. The objective of this research was to assess the main indicators of oxidative stress detected in the saliva of dogs and to compare them to the degree of inflammation and tartar amount on their teeth and gums. By identifying these correlations, we intended to identify early-stage PD markers that would allow us to diagnose the condition in dogs without requiring for invasive or traumatic procedures. The antioxidant enzyme superoxide dismutase (SOD), total antioxidant capacity (TAC), malondialdehyde (MDA) and 8-hydroxyguanosine (8OHG), matrix metalloproteinase-8 (MMP8), and the quantity of total proteins are the markers that have been investigated in order to accomplish these objectives. The appearance of specific forms of periodontal disease has been confirmed by an increase in the saliva concentration of MMP8, a marker commonly used in the diagnosis of these pathologies in humans. The study was carried out on 22 dogs divided in a control group (C) and study groups (S), the second one being divided into three subgroups according to the severity of the gum inflammation and the presence or absence of tartar: S1-small accumulation of tartar, lack of infection-related signs; S2-moderate accumulation of tartar, gums swollen, red, and bled easily; S3-significant accumulation of tartar; gums bright red and bleeding; marked pain and halitosis. A correlation between the concentration of the tested parameters and the severity of the local appearance of the gum and teeth was noted. In comparison to the results of individuals from the control group, MMP8 reported increases of 1.2, 2, and 3.7 times, respectively, in the case of individuals from subgroups S1, S2, and S3. Oxidative stress is caused by inflammatory processes in the oral cavity. The presence of oxidative stress was demonstrated by the evaluation of different indicators in the saliva: an increase in the general antioxidant status, which was associated with an increase in SOD activity; intensification of the lipid peroxidation processes, as demonstrated by the accumulation of the MDA peroxidation product; and an increase in the DNA oxidation processes, as demonstrated by the accumulation of the oxidation product 8OHdG. In consequence, it was observed that there were up to 2-fold increases in protein levels, total antioxidant activity, SOD, and MDA, and up to 8.6-fold increases in the case of 8-OHdG when comparing dogs from the S3 group (significant tartar accumulation; bright red and bleeding gums; marked pain and halitosis) to those in the control group.
Keywords: MMP8; dog; oxidative stress; periodontal disease.