Treatment with SRL172 (heat-killed Mycobacterium vaccae) inhibits progression of established experimental periodontal disease in Wistar rats

Vaccination against periodontitis: the saga continues

Periodontal disease can be considered to be one of the most common chronic inflammatory diseases inflicting humans. With the advent of advanced molecular diagnostic techniques, a better understanding of the role of specific pathogens and the contributory role of the host immune response in the initiation and progression of periodontal disease has been possible - although not completely. However, successful vaccine development that fully utilizes the current level of understanding has not yet occurred for human use. This paper reviews various in vitro, animal studies and human trials undertaken to develop a vaccine against periodontal disease, with emphases on the shortfalls of these efforts and future prospects of developing a successful vaccine against periodontal disease.

Soluble beta-1,3/1,6-glucan from yeast inhibits experimental periodontal disease in Wistar rats

OBJECTIVE

We have investigated whether a purified immunomodulatory water soluble beta-1,3/1,6-glucan isolated from the cell wall of Bakers yeast, Saccharomyces cerevisiae, would influence the progression of ligature-induced periodontal disease, and to modulate accompanying cytokine and hypothalamic-pituitary-adrenal (HPA) axis responses to a lipopolysaccharide (LPS) challenge.

MATERIAL AND METHODS

beta-1,3/1,6-glucan (10 mg/kg/day) was given in the drinking water to Wistar rats during the entire experiment, starting 14 days before disease induction, while control rats were given tap water only. Periodontal disease was assessed when the ligatures had been in place for 35 days.

RESULTS

Orally administered soluble beta-1,3/1,6-glucan significantly reduced periodontal bone loss as measured on digital X-rays (p=0,026). Glucan-treated rats also showed a significantly enhanced plasma level of the HPA axis-driven hormone corticosterone (p=0.047), and of the cytokine transforming growth factor-1beta (p=0.032), as well as a tendency to enhanced IL-10 (p=0.106), induced by intra-peritoneally administered LPS.

CONCLUSION

Soluble beta-1,3/1,6-glucan administered by the oral route diminishes ligature-induced periodontal bone loss in this model. This effect may be attributable to the well documented ability of beta-1,3/1,6-glucan to stimulate macrophage phagocytosis and to skew the T helper (Th)1/Th2 balance towards Th1 and T regulatory responses. The HPA axis may play a significant role in beta-1,3/1,6-glucan induced immune modulation.

Chronic treatment with the glutamate receptor antagonist MK-801 alters periodontal disease susceptibility

OBJECTIVE

Previous experiments in rats suggest that hypothalamic-pituitary-adrenal (HPA) axis over-responsiveness, which leads to increased secretion of immunoregulatory glucocorticoid hormones, increases periodontal disease susceptibility, whereas HPA axis under-responsiveness is associated with increased resistance to the disease. The present study was designed to investigate whether MK-801 (dizocilipine malate), an antagonist of the glutamate receptor N-methyl-D-aspartate (NMDA) in the brain, which has been found to play an important role in the regulation of the HPA axis, would influence the outcome of experimental ligature-induced periodontal disease in a rat model.

METHODS

Experimental periodontal disease was induced in periodontal disease susceptible and HPA axis high-responding Fischer 344 rats 2 days before chronic treatment with MK-801(1 mg/kg intraperitoneally). The periodontal breakdown was assessed after the ligatures had been in place for 23 days. Following intraperitoneal Gram-negative bacterial lipopolysaccharide stimulation (Escherichia coli, 250 microg/kg), concentrations of glucocorticoid receptors (GRs) in the hippocampus, and levels of the cytokine tumour necrosis factor alpha (TNF-alpha), as well as the HPA axis-derived hormone corticosterone, were measured in serum.

RESULTS

Compared to vehicle-treated controls, MK-801-treated rats had significantly increased periodontal tissue destruction (p < 0.01). MK-801-treated rats also showed significantly increased expression of GRs in the hippocampus (p < 0.05), elevated levels of corticosterone (p < 0.001) and reduced levels of TNF-alpha (p < 0.01) in serum 2 h after lipopolysaccharide stimulation.

CONCLUSION

These findings may implicate glutamate receptor-dependent mechanisms in periodontal disease, and support the concept of a bidirectional immune-brain-immune regulatory network with importance for periodontal health and disease.

Chronic glycine treatment inhibits ligature-induced periodontal disease in Wistar rats

OBJECTIVE

Dysregulation of immune and stress responses plays a significant role for the development and progression of inflammatory diseases, including periodontal disease. The non-essential amino acid glycine modulates immune and central nervous system (CNS) responses, and has been shown to beneficially affect tissue destructive inflammatory conditions. The purpose of this study was to test the ability of orally administered glycine to influence periodontal disease progression, as well as immune and hypothalamic-pituitary-adrenal (HPA) responses following lipopolysaccharide stimulation.

METHODS

Glycine was supplied in the drinking water during the whole experiment to male Wistar rats, starting 3 days before the induction of experimental ligature-induced periodontal disease. Control rats were given tap water only. The periodontal breakdown was assessed after the ligatures had been in place for 34 days. Following intraperitonal lipopolysaccharide stimulation, concentrations of the proximal cytokines tumour necrosis factor-alpha (TNF-alpha) and interleukin-10, as well as the HPA axis-derived hormone corticosterone, were measured in blood serum.

RESULTS

Orally administered glycine significantly reduced periodontal bone loss as measured by digital X-rays (p = 0.007). Bone loss was negatively correlated with increased serum glycine, whereas no significant relationship was found with TNF-alpha, interleukin-10, or corticosterone.

CONCLUSION

Chronic ingestion of glycine supplied in the drinking water significantly reduced periodontal bone loss. No effect of glycine on immune and HPA-axis responses was revealed. Further studies are needed to clarify the mechanisms of action.

Oral treatment with SRP299 (killed Mycobacterium vaccae ) inhibits experimental periodontal disease in Wistar rats

OBJECTIVE

Mycobacterium vaccae injected subcutaneously was previously shown to prevent and treat ligature-induced periodontal disease (PD) in Wistar rats (Breivik & Rook 2000, 2002). Since mycobacteria are readily taken up via Peyer's patches in the intestine, we have now tested the ability of oral SRP299 (killed M. vaccae) to prevent ligature-enhanced PD in Wistar rats, and to modulate the accompanying cytokine and corticosterone responses.

MATERIAL AND METHODS

A single oral dose of SRP299 (1 mg) was given 14 days before the application of ligatures. PD was assessed when the ligatures had been in place for 56 days.

RESULTS

Oral SRP299 reduced bone loss (p = 0.036, X-ray; p = 0.061, histometry) and fibre loss, both on the ligatured (p = 0.0047) and control (p = 0.005) sides, and also reduced the level of TNF-alpha (p = 0.0137) and corticosterone (p = 0.048) induced by intraperitoneal endotoxin lipopolysaccharide (LPS).

CONCLUSIONS

SRP299 administered by the oral route diminishes ligature-induced bone and fibre loss in this model. This effect may be attributable to the known ability of SRP299 to evoke regulatory T cells, although the mechanism could not be investigated in this study. Treated rats also had less excitable hypothalamo-pituitary-adrenal (HPA) axes. HPA axis overactivity is a known risk factor in human PD. Trials of SRP299 in human PD are now justified.