Exposure of Porphyromonas gingivalis to cortisol increases bacterial growth

https://doi.org/10.1016/j.archoralbio.2013.09.003Get rights and content

Abstract

Objective

Psychological stress is considered as a risk factor for periodontal diseases. The stress-related hormone, cortisol is one of the main molecules released during human stress response and is found in plasma and gingival crevicular fluid. This hormone has been suggested to modify composition of subgingival biofilms. The aim of this study was to investigate the effect of exposure to cortisol on Porphyromonas gingivalis (P. gingivalis) growth.

Materials and methods

P. gingivalis ATCC strain 33277 was cultured under strict anaerobic conditions at 37 °C in Brain Heart Infusion medium supplemented with hemin (5 μg ml−1) and menadione (1 μg ml−1). Bacterial cultures were incubated with or without hydrocortisone (0.04–10 μg ml−1) at 37 °C for 12, 24 and 48 h and bacterial growth was evaluated by spectrophotometric method (OD600 nm). Cortisol consumption has been followed by HPLC.

Results

Cortisol significantly increased P. gingivalis growth in the first 24 h peaking at 12 h but this increase was not related to the concentration used. During the time period, no consumption of cortisol was observed.

Conclusions

This study provides further support for the idea that stress-induced hormone; cortisol may influence the growth of P. gingivalis. This specific effect may be involved in the relationship between stress and periodontal diseases.

Introduction

Periodontal diseases are inflammatory diseases of tooth supporting tissues induced by oral bacterial biofilms.1 Development of these diseases involves several bacterial species such as Porphyromonas gingivalis (P. gingivalis), Prevotella intermedia, Treponema denticola or Aggregatibacter actinomycetemcomitans within subgingival biofilm as well as host response.2 Several local, systemic and environmental risk factors such as oral hygiene, smoking, diabetes mellitus are known to affect subgingival biofilm's composition and increase the severity of periodontal destruction.3 Additionally, consequences of stress on lifestyle (less oral hygiene, high-fat diet) are indirect effects that could worsen different types of manifestations such as plaque accumulation and gingival inflammation.4 In a clinical study, academic stress was suggested to affect periodontal health, as shown by more plaque accumulation and more pronounced gingival inflammation during the examination period of students.5

In response to stressful events, several stress markers such as cortisol, catecholamines, chromogranin A, salivary alpha-amylase are released after the stimulation of central and autonomous nervous system.6 These stress markers are found in blood, saliva and gingival crevicular fluid (GCF) and may influence the inflammatory processes and development of periodontal diseases.7

Cortisol is one of the most extensively studied stress-related hormone. Cortisol is a glucocorticoid hormone and is secreted by the stimulation of hypothalamus-pituitary-adrenal (HPA) axis in response to psychological stress. Salivary level of cortisol reliably reflects HPA axis activity and is used as a biological marker of stress in human psychological studies.8 In a recent clinical study including individuals with salivary cortisol levels varying between 0.006 and 0.015 μg/mL depending on the severity of periodontitis and depression, it was suggested that a high salivary cortisol level may show an increased risk for chronic periodontitis.9 Interestingly, significant associations between serum cortisol levels and periodontitis severity characterized by increased pocket depth, clinical attachment loss and bleeding on probing10 but also increased secretion of pro-inflammatory cytokines particularly interleukin-6 (IL-6) has also been reported.11

Since the introduction of the microbial endocrinology concept,12 studies have focused on the effects of stress hormones on bacterial growth and virulence.13, 14 Analysis of the effect of catecholamines15 and cortisol16 on the growth of periodontal bacteria has demonstrated the direct role of stress hormones on bacterial growth in subgingival biofilm. Noradrenalin reduces growth of P. gingivalis and Aggregatibacter actinomycetemcomitans but increases growth of other species such as Eikenella corrodens.15 Although growth reduction of P. gingivalis occurred, it has been shown that cathecolamines induce bacterial phenotypic change and increase in vitro activity of virulence factors.17 Bacteria in dental plaque have been recognized as the primary etiological agents of periodontal diseases.1 The concept of microbial endocrinology12 was introduced several decades after this recognition and possible correlations between elevated hormone levels and composition of subgingival microbiota have received attention by the field of periodontology. Mechanisms involved in these interactions remain so far unclear. The aim of the present study was to investigate the effect of exposure to cortisol on P. gingivalis growth over time.

Section snippets

Bacterial strain

The P. gingivalis strain ATCC 33277 was purchased from ATCC and was cultivated under strict anaerobic conditions at 37 °C in Brain Heart infusion1 supplemented with hemin (5 μg ml−1) and menadione (1 μg ml−1) both from Sigma.

Influence of cortisol on bacterial growth

Prior to the growth test, P. gingivalis culture was evaluated by OD600 nm. First, a pilot study was conducted in order to determine the optimum hydrocortisone1 concentrations to be used. A total of 15 different hydrocortisone

Influence of cortisol on bacterial growth

First, we assessed the effect of cortisol on bacterial growth. P. gingivalis cultures were challenged by hydrocortisone at different concentrations. At 12-h, all the hydrocortisone concentrations tested (0.04–10 μg ml−1) resulted in an increase in the bacterial growth in comparison with the control. This increase was between 24% and 45% depending on the hydrocortisone concentration at this time. Hydrocortisone increased bacterial growth in a dose-independent manner (p = 0.967) (Fig. 1).

Effect of hydrocortisone on P. gingivalis growth decreases with time

The effect

Discussion

In the present study, we investigated possible effects of cortisol on the growth of P. gingivalis. The growth rate of P. gingivalis was significantly increased after addition of cortisol in the culture medium at 12 h and 24 h in a dose-independent manner. This finding suggests that stress-induced hormone cortisol may have a specific effect on the growth of P. gingivalis. Despite the increase in growth rate, HPLC experiments demonstrated that total amount of cortisol was stable at all time-points

Funding

This study has been support by author's institution.

Competing interests

None.

Ethical approval

Not required.

Author contributions

Aliye Akcali and Olivier Huck contributed to the design of the study, the experiments and manuscript writing. Nurcan Buduneli, Jean-Luc Davideau and Henri Tenenbaum contributed to the design of the study and the manuscript writing. Timur Köse performed statistical analysis.

Acknowledgement

The authors thank Dr. Cynthia Atindehou for her help in HPLC analysis.

References (30)

  • S.S. Dickerson et al.

    Acute stressors and cortisol responses: a theoretical integration and synthesis of laboratory research

    Psychol Bull

    (2004)
  • Z. Refulio et al.

    Association among stress, salivary cortisol levels, and chronic periodontitis

    J Periodontal Implant Sci

    (2013)
  • A. Ishisaka et al.

    Association of cortisol and dehydroepiandrosterone sulphate levels in serum with periodontal status in older Japanese adults

    J Clin Periodontol

    (2008)
  • A. Johannsen et al.

    Gingival inflammation, increased periodontal pocket depth and elevated interleukin-6 in gingival crevicular fluid of depressed women on long-term sick leave

    J Periodontal Res

    (2007)
  • M. Lyte

    The role of microbial endocrinology in infectious disease

    J Endocrinol

    (1993)
  • Cited by (17)

    • Is oral health affected in long period space missions only by microgravity? A systematic review

      2020, Acta Astronautica
      Citation Excerpt :

      In this line of evidence, a study showed that the growth rate of P. gingivalis was significantly increased after addition of cortisol in the culture medium at12 h and 24 h in a dose-independent manner. This finding suggests that stress-induced hormone cortisol may have a specific effect on the growth of P. gingivalis [37]. In a study including six crewmembers, 3 men and 3 women, at the Mars Desert Research Station (MDRS) during two weeks-short period, salivary cortisol, alpha-amylase levels, and current stress scores were shown to be significantly higher after the end of the mission compared to before the start of the mission.

    • In-situ forming implants loaded with chlorhexidine and ibuprofen for periodontal treatment: Proof of concept study in vivo

      2019, International Journal of Pharmaceutics
      Citation Excerpt :

      Prior to evaluating the effect of the ISFI on P. gingivalis growth, bacterial growth was evaluated at OD600 nm using a spectrophotometer. P. gingivalis growth was recorded in bacterial culture medium (control), placebo ISFI, CHX-IBU ISFI release media respectively and compared to determine the effect of CHX-IBU ISFI as described previously (Akcali et al., 2014). Growth rate was evaluated at 6, 9, 24 and 48 h (Fig. 1).

    • Physiological Adaptations of Key Oral Bacteria

      2014, Advances in Microbial Physiology
      Citation Excerpt :

      It has also been considered for some time that increased stress is a mitigating factor reducing the success of periodontal treatment (Vettore, Quintanilha, Monteiro da Silva, Lamarca, & Leão, 2005). It is therefore of interest that recent studies have identified that cortisol seems to affect the growth of a range of periodontal pathogens in vitro (Akcalı et al., 2014; Jentsch, März, & Krüger, 2013), while other hormones such as adrenaline seem to increase expression of several potential virulence factors (Graziano et al., 2013). While these data are somewhat limited and do not all agree with each other, it would be of great interest to discern if the oral microbiota does alter in response to long-term psychological stress on the subject.

    View all citing articles on Scopus
    View full text