Inorganic Chemistry of Defensive Peroxidases in the Human Oral Cavity

Abstract

The innate host response system is comprised of various mechanisms for orchestrating host response to microbial infection of the oral cavity. The heterogeneity of the oral cavity and the associated microenvironments that are produced give rise to different chemistries that affect the innate defense system. One focus of this review is on how these spatial differences influence the two major defensive peroxidases of the oral cavity, salivary peroxidase (SPO) and myeloperoxidase (MPO). With hydrogen peroxide (H2O2) as an oxidant, the defensive peroxidases use inorganic ions to produce antimicrobials that are generally more effective than H2O2 itself. The concentrations of the inorganic substrates are different in saliva vs. gingival crevicular fluid (GCF). Thus, in the supragingival regime, SPO and MPO work in unison for the exclusive production of hypothiocyanite (OSCN−, a reactive inorganic species), which constantly bathes nascent plaques. In contrast, MPO is introduced to the GCF during inflammatory response, and in that environment it is capable of producing hypochlorite (OCl−), a chemically more powerful oxidant that is implicated in host tissue damage. A second focus of this review is on inter-person variation that may contribute to different peroxidase function. Many of these differences are attributed to dietary or smoking practices that alter the concentrations of relevant inorganic species in the oral cavity ( e.g.: fluoride, F−; cyanide, CN−; cyanate, OCN−; thiocyanate, SCN−; and nitrate, NO3−). Because of the complexity of the host and microflora biology and the associated chemistry, it is difficult to establish the significance of the human peroxidase systems during the pathogenesis of oral diseases. The problem is particularly complex with respect to the gingival sulcus and periodontal pockets (where the very different defensive stratagems of GCF and saliva co-mingle). Despite this complexity, intriguing in vitro and in vivo studies are reviewed here that reveal the interplay between peroxidase function and associated inorganic chemistry.

Influence of a model human defensive peroxidase system on oral streptococcal antagonism

“…the gingival sulcus), it is disfavoured in the part of the oral Abbreviations: bLPO, bovine milk lactoperoxidase; CLSM, confocal laser scanning microscopy; CV, crystal violet; DTNB, 5,59-dithio-bis(2-nitrobenzoic acid); hMPO, human myeloperoxidase; HRP, horseradish peroxidase; hSPO, human salivary peroxidase; LPO, lactoperoxidase. (Ashby, 2008). We have employed bovine milk lactoperoxidase (bLPO), a readily available enzyme, as a surrogate for hSPO.…”

“…the gingival sulcus), it is disfavoured in the part of the oral cavity that is controlled by saliva (Ashby, 2008). Instead, hSPO and hMPO work in unison in the supragingival regime to exclusively oxidize thiocyanate (SCN 2 ) to produce hypothiocyanite (OSCN 2 , a reactive inorganic species), which constantly bathes early oral plaques (Ashby, 2008). We have employed bovine milk lactoperoxidase (bLPO), a readily available enzyme, as a surrogate for hSPO.…”

“…The effects of the host immune system on oral biofilms are less well understood. This paper focuses on the influence of defensive peroxidases on interstreptococcal interactions.There are two host-derived defensive peroxidases in the human oral cavity, salivary peroxidase (hSPO) and myeloperoxidase (hMPO) (Ashby, 2008;Ihalin et al, 2006). hSPO is a normal non-inducible component of the saliva of the parotid and submandibular glands (Riva et al, 1978), whereas hMPO is an offensive mechanism of neutrophilic polymorphonuclear leukocytes (PMNs).…”

Evaluation of the nitrate and nitrite content of vegetables commonly grown in Slovenia

“…The nitrate (NO3 -) nitrogen (N) form has a low level of acute toxicity but it can be transformed into the nitrite N (NO2 -) form, which has much higher acute toxicity (Santamaria, 2006). It has been estimated that about 4-8% of the nitrate from the diet may be reduced to nitrite by the micro flora in the oral cavity (Ashby, 2008;Lundberg and Weitzberg, 2009). Some studies have shown that nitrate exposure is correlated with gastric cancer risk due to the endogenous formation of N-nitroso compounds (Jakszyn and González, 2006).…”

Stabilizing Sodium Hypochlorite at High pH: Effects on Soft Tissue and Dentin

“…NaOH-stabilized sodium hypochlorite could have a stronger tissue-dissolving effect compared to the standard preparation. The reason for this is that the OCl -/HOCl equilibrium adjusts itself exceedingly fast in non-stabilized solutions (13). In contact with microorganisms or tissues, the pH drops, so that…”