Lipid Peroxides in Middle Ear Fluid after Acute Otitis Media in Guinea Pigs

Abstract

Oxygen free radical damage has been demonstrated in the middle ear mucosa of a guinea pig model of acute otitis media (AOM). Potential sources of free radicals include both neutrophils responding to infection and Streptococcus pneumoniae, a common AOM pathogen. This project was conducted to examine the middle ear fluid in a guinea pig model of AOM for evidence of elevated lipid peroxide (LPO) as a marker of free radical damage. Twenty-one guinea pigs were injected transtympanically with bacteria into the left (infected) middle ear cavity and sterile saline into the right (control) middle ear. Middle ear fluid was recovered on postoperative day 5. The fluid was weighed and analyzed for quantity of LPO. Results indicated an increased absolute level of LPO, as well as an increased level of LPO divided by the weight of the fluid recovered. Histologic examination confirmed leukocyte infiltration and mucosal edema that were consistent with mucosal damage. While free radical damage to the middle ear mucosa in a guinea pig model of AOM is well documented, this is the first study to demonstrate evidence of free radical damage in middle ear fluid. These results are relevant because they correlate mucosal damage with lipoperoxidation in fluid. Additionally, this serves as an important precursor to human studies, since middle ear fluid is readily available in patients with otitis media.

The Role of Free Radicals in Chronic Rhinosinusitis

“…It is important to note, however, that freezing was also used in the storage of samples during previous experiments in our laboratory, experiments that did demonstrate a difference in free radical-mediated damage. [2][3][4][5][6] Although this study showed no statistically significant difference in LPO content between healthy and diseased tissue in chronic rhinosinusitis, perhaps the difference, if it exists at all, is smaller and therefore more difficult to detect than that which has been shown in OM. While the neutrophil respiratory burst is a part of the inflammatory response and contributes to free radical formation in OM and rhinosinusitis, S pneumoniae, the other source of free radicals in OM, may not play as large a role in chronic rhinosinusitis.…”

“…1 Free radical-mediated damage has been characterized in the pathogenesis of more than 100 disorders including stroke, atherosclerosis, myocardial infarction, autoimmune diseases, and nervous system disorders. 1 Studies in our laboratory have implicated free radicals in otitis media (OM) in animal models [2][3][4][5] and humans. 6 Neutrophils, in their respiratory burst, and Streptococcus pneumoniae, the most common pathogen in acute OM, 7 are thought to generate the damaging species in this infection.…”

Oxidant and antioxidant levels in children with acute otitis media and tonsillitis: A comparative study

“…Furthermore, when compared the AOM and AT groups, there was statistically significant difference between the groups (Table 1). Many investigators, both experimental [16][17][18][19][20] and human [21][22][23][24][25] studies have measured lipid peroxidation levels in AOM and acute or chronic tonsillitis. These studies also demonstrated that increased oxidative stress in the both diseases.…”

Effect of Ginkgo Leaf Parenteral Solution on Blood and Cochlea Antioxidant and Immunity Indexes in OM Rats

“…MDA, an end product of membrane lipid peroxidation, is one of the most widely used markers for free radical mediated damage. Many investigators have measured lipid peroxidation levels in AOM and acute or chronic tonsillitis in both experimental [ 25 , 26 , 27 , 28 , 29 ] and human [ 30 , 31 , 32 , 33 , 34 ] studies. These studies also demonstrated that increased oxidative stress in the both diseases.…”