The Effect of Stress on the Inflammatory Response toPorphyromonas gingivalisin a Mouse Subcutaneous Chamber Model

Season and sex have different effects on hematology and cytokines in striped hamsters (Cricetulus barabensis)

Animals in the temperate zones face seasonal variations in environments and hence their immune responses change seasonally. In the current study, seasonal changes in hematological parameters and cytokines in striped hamsters (Cricetulus barabensis) were examined to test the winter immunoenhancement hypothesis, which states that immune function tends to increase in fall and winter compared with other seasons. Male and female hamsters were captured from the wild in the fall and winter of 2014 and in the spring and summer of 2015. Maximum body mass in both sexes and relative fatness in female hamsters occurred in the summer, indicating that body condition was the best during this season. All hematological parameters were not different between male and female hamsters, and were also not affected by the interaction of season and sex except neutrophil granulocytes (GRAN). Red blood cells (RBC) and haematocrit (PCV) were higher in the fall and winter, and hemoglobin concentration (HGB) was the highest in winter in hamsters compared with the spring and summer, implying that their oxygen-carrying capacity and oxygen affinity of the blood increased during these seasons. Compared with other seasons, the number of white blood cells (WBC) was higher in winter than in summer, intermediate granulocytes (MID), the percent of MID (MID%), GRAN and the percent of GRAN (GRAN%) were the highest in winter, which all supported the winter immunoenhancement hypothesis. However, the count of lymphocytes (LYMF) was the highest in spring, being inconsistent with this hypothesis. IL-2 levels, but not TNF-α, were influenced by seasons, sex and their interaction in hamsters. Regardless of sex, IL-4 titres were higher in spring and summer than in fall and winter in hamsters. INF-γ titres in male hamsters did not differ between the spring and summer, while its titres in female hamsters was lower in spring in contrast with winter and summer. Higher IL-2 and IL-4 levels during the breeding seasons might be crucial in controlling the increased possibilities of infections in these seasons. In summary, season and sex had disparate effects on different hematological profiles and the levels of cytokines in hamsters.

Acute cold stress improved the transcription of pro-inflammatory cytokines of Chinese soft-shelled turtle against Aeromonas hydrophila

Chinese soft-shelled turtle, Pelodiscus sinensis, is widely cultured in East and Southeast Asian countries. It frequently encounters the stress of abrupt temperature changes, which leads to mass death in most cases. However, the mechanism underlying the stress-elicited death remains unknown. We have suspected that the stress impaired the immune function of Chinese soft-shelled turtle, which could result in the mass death, as we noticed that there was a clinical syndrome of infection in dead turtles. To test our hypothesis, we first performed bioinformatic annotation of several pro-inflammatory molecules (IL-1β, TNFα, IL-6, IL-12β) of Chinese soft-shelled turtle. Then, we treated the turtles in six groups, injected with Aeromonas hydrophila before acute cold stress (25 °C) and controls, after acute cold stress (15 °C) and controls as well as after the temperature was restored to 25 °C and controls, respectively. Subsequently, real-time PCR for several pro-inflammatory cytokines (IL-1β, TNFα, IL-6, IL-12β, IL-8 and IFNγ) was performed to assess the turtle immune function in spleen and intestine, 24 hours after the injection. We found that the mRNA expression levels of the immune molecules were all enhanced after acute cold stress. This change disappeared when the temperature was restored back to 25 °C. Our results suggest that abrupt temperature drop did not suppress the immune function of Chinese soft-shelled turtle in response to germ challenge after abrupt temperature drop. In contrast, it may even increase the expression of various cytokines at least, within a short time after acute cold stress.

Association between mental well-being, depression, and periodontal attachment level among young adults of the postwar Sebha city, Libya: A pilot study

OBJECTIVES

The present study was aimed to investigate the association of mental well-being and depression with periodontal clinical attachment loss among young adults in postwar urban population of Sebha city, Libya.

MATERIALS AND METHODS

Mental well-being and depression were assessed using Arabic versions of World Health Organization (WHO) five well-being index and major depression inventory (ICD-10), respectively. Random sample of 149 subjects were studied. Degree of periodontal attachment was measured at six sites per tooth using a rigid manual periodontal probe.

RESULT AND CONCLUSION

A total of 59.11% of the studied samples had healthy mental well-being state, whereas 40.81% had poor mental well-being. The severity of depression was stronger in males than in females. In the present study mental well-being, depression, and all its categories did not have any significant effect on periodontal attachment loss. Further studies and health interventions can be planned based on this data.

The role of RgpA in the pathogenicity of Porphyromonas gingivalis in the murine periodontitis model

AIM

To investigate the in vivo role of gingipains in Porphyromonas gingivalis' virulence, and suggest a possible host mechanisms through which the bacteria cause alveolar bone loss.

MATERIALS AND METHODS

Mice were orally infected with P. gingivalis wild type, or the gingipains mutants (RgpA⁻, Kgp⁻, RgpA⁻/Kgp⁻). Mice were analysed for alveolar bone loss using micro-computed tomography. The molecular effects of the proteases were evaluated using the subcutaneous chamber model. Mice were infected with P. gingivalis wild type or mutants. Exudates were analysed for cytokine and leukocytes levels, in vivo phagocytosis, P. gingivalis survival and serum anti-P. gingivalis IgG titres.

RESULTS

Only RgpA-expressing bacteria induced significantly alveolar bone loss, and suppressed phagocytosis resulting in increased survival of P. gingivalis in the chamber exudates. In addition, RgpA-expressing bacteria induced higher levels of leukocytes and cytokines 2 h post-infection, and reduced levels of serum anti-P. gingivalis IgG titres 7 days post-infection.

CONCLUSIONS

Our findings showed that elimination of RgpA from P. gingivalis diminished inflammation, but augmented phagocytosis and antibody titres, coincidental with reduced alveolar bone loss. These findings support the hypothesis that RgpA is a critical virulence factor in the pathogenesis of experimental periodontitis in mice.

Histometric analysis of ligature-induced periodontitis in rats: a comparison of histological section planes

The purpose of this study was to analyze the histometry of ligature-induced periodontitis in rats at different histological section depths. Sixteen male adult Wistar rats were randomly assigned to two groups: ligature and control. In the ligature group, rats received a sterile 4/0 silk ligature around the maxillary right 2nd molar. Thirty serial sections containing the 1st and 2nd molars, in which the coronal and root pulp, cementoenamel junction (CEJ) in the mesial side of the 2nd molar, interproximal alveolar bone and connective fiber attachment were clearly visible, were selected for histometric analysis. The histological sections were clustered in groups of 10 sections corresponding the buccal (B), central (C) and lingual (L) regions of the of periodontal tissue samples. The distance between the CEJ in the mesial side of the 2nd molar and the attached periodontal ligament fibers (CEJ-PL) as well as the distance between the CEJ and the alveolar bone crest (CEJ-BC) were determined. From CEJ-PL and CEJ-BC distances measured for each specimen, the measurements obtained in the B, L and C regions were recorded individually and together. Data were submitted to statistical analysis. Significant differences (p<0.001) were observed between the control and ligature groups regarding CEJ-PL (0.05 mm and 0.26 mm, respectively) and CEJ-BC (0.47 mm and 0.77 mm, respectively) measurements. Regarding the depth of the buccal, central and lingual planes, the means of CEJ-PL and CEJ-BC of both groups showed no statistically significant differences (p>0.05). In conclusion, the selection of 10 serial sections of the central region of periodontal tissue samples at any depth can be considered as representative for the evaluation of periodontal ligament fiber attachment and bone loss in ligature-induced periodontitis in rats.

Evaluation of blood vessel ingrowth in fibrin gel subject to type and concentration of growth factors

Our aim was to quantitatively assess the angiogenetic effects of VEGF and bFGF immobilized in a fibrin-based drug delivery system in a suitable subcutaneous rat model. After evaluation of a suitable implantation technique (6 rats), four teflon isolation chambers containing fibrin gel matrices were implanted subcutaneously in an upside-down fashion on the back of 30 Lewis rats. The matrices consisted of 500 μl fibrin gel with two different fibrinogen concentrations (10 mg/ml or 40 mg/ml fibrinogen) and 2 I.U./ml thrombin and contained VEGF and bFGF in five different concentrations (0 to 250 ng/ml each). At 3, 7 and 14 days after implantation, matrices were explanted and subjected to histological and morphometrical analysis. At 1 week, the volume of the fibrin clots was significantly smaller in the 100 and 250 ng/ml VEGF and bFGF groups in comparison to lower concentrated growth factors. At 1 and 2 weeks, the use of growth factors in low concentrations (25 ng/ml VEGF and bFGF) significantly increased the amount of fibrovascular tissue, average fraction of blood vessels and number of blood vessels at the matrix–host interface in comparison to growth factor-free controls. Higher concentrations were neither associated with further increase of tissue formation nor with increased sprouting of blood vessels in this model. This study demonstrates that fibrin gel-immobilized angioinductive growth factors efficiently stimulate generation of fibrovascular tissue and sprouting of blood vessels in a newly developed subcutaneous upside-down isolation chamber model with an optimum between 25 and 100 ng/ml.

Reduced expression of gamma interferon in serum and marked lymphoid depletion induced by Porphyromonas gingivalis increase murine morbidity and mortality due to cytomegalovirus infection

Porphyromonas gingivalis, a gram-negative anaerobe, is a major etiological agent of severe forms of periodontal disease. Although periodontal disease is considered a localized disease, accumulating evidence indicates that it may lead to a predisposition to a decline in immunocompetence. Human cytomegalovirus (CMV) commonly infects all human populations without producing significant clinical symptoms. Immunocompromised patients usually develop a primary or reactivated CMV infection, which is associated with high rates of morbidity and mortality. The aim of this study was to determine whether P. gingivalis increases animal susceptibility to CMV infection. Mice were inoculated with CMV and infected locally with P. gingivalis 3 days after the virus inoculation. Mortality rates were monitored, and traces of viral DNA and bacterial infection were detected systemically by using real-time PCR. Local and systemic cytokine secretion was measured, and histological sections were used to assess the pathological state of infected organs. P. gingivalis- and CMV-coinfected mice showed dramatically higher mortality rates than mice infected with P. gingivalis or CMV only. Although the organs of coinfected mice exhibited decreased viral titers, distinct necrosis and tissue damage were more evident in the livers and spleens of these mice than in those of mice infected with CMV only. Furthermore, systemic gamma interferon levels were decreased in coinfected mice, and marked lymphoid depletion was observed in their necrotic organs. In parallel control Escherichia coli-CMV coinfection experiments, the mortality and pathological results were the same as those found in mice infected with CMV only. Our results suggest a specific influence of P. gingivalis on the mouse immune response, causing increased susceptibility to CMV infection.

Substance P enhances the inhibition of osteoblastic cell differentiation induced by lipopolysaccharide from Porphyromonas gingivalis

BACKGROUND

Substance P (SP) is a multifunctional neuropeptide that transmits pain signals, regulates the immune system, and may modulate emotional stress. SP stimulates bone resorption activity of osteoclasts, and SP level in gingival crevicular fluid is correlated with the degree of periodontal inflammation. However, the exact roles of SP in bone metabolism and periodontal diseases are poorly understood. To elucidate the effect of stress on bone metabolism, we investigated the effect of SP on osteoblastic cell differentiation in the presence of lipopolysaccharide from Porphyromonas gingivalis (P-LPS).

METHODS

The primary osteoblastic cells were isolated from fetal rat calvaria (RC) and cultured with SP, P-LPS, and an SP antagonist (SPa). The effects of SP on bone nodule (BN), alkaline phosphatase (ALPase) activity, mRNA expressions of SP receptor, bone matrix proteins, and Cbfa 1 were investigated.

RESULTS

SP stimulated the expression of SP receptor mRNA in RC cells and enhanced its expression in the presence of P-LPS (50 ng/ml). SP inhibited BN formation and ALPase activity in a dose-dependent manner (10(-7) to 10(-5) M) and further suppressed mRNA expression of bone sialoprotein, osteopontin, and osteocalcin but not of type I collagen mRNA. The inhibitory effects were enhanced in the presence of P-LPS and blocked by Spantide III. Furthermore, the expression of Cbfa 1 mRNA was also markedly suppressed in the presence of SP and P-LPS.

CONCLUSION

These findings suggest that SP inhibits osteoblastic cell differentiation and may be related to bone metabolism in periodontal diseases under conditions of stress.

Effect of variable moderate chronic stress on ligature-induced periodontal disease in Wistar rats

The aim of this investigation was to study the impact of stress on ligature-induced periodontal disease in rats by means of a variable moderate chronic stress model. Thirty male Wistar rats were randomly assigned to six groups. Control groups received only ligatures around the second maxillary molars, while experimental groups were exposed to stress in additional. Stress was imposed by means of flashing light, isolation, rat blood smelling, new environment exposure, immobilization in cold temperature and immobilization at room temperature. Stress was applied randomly, thereby diminishing adaptation of the animals to the model. The animals were killed after 29, 43, and 57 days. The distance between the cementum-enamel junction and the alveolar bone (CEJ-AB) was measured. Alveolar bone loss was statistically different between stressed and control animals, whereas differences were not observed between experimental periods. The mean CEJ-AB distance in animals exposed to stress was 154.50 microm smaller than the corresponding distance in the controls. It might be concluded that variable moderate chronic stress decreased alveolar bone loss in a ligature-induced periodontal disease model.

The effect of chronic emotional stress on the humoral immune response to Porphyromonas gingivalis in mice

Previous studies have shown that psychological stress plays a significant role in the outcome of infectious diseases, but data related to the effect of stress on periodontal infection is limited. The present study was designed to test the impact of emotional stress on the humoral immune response to the periodontal pathogen Porphyromonas gingivalis in a mouse model of local inflammation. Chambers constructed from titanium wire were implanted in the subcutaneous dorsolumbar region of mice. All mice were immunized with P. gingivalis followed by an intrachamber challenge with the bacteria. One group of mice was used as control, while the other two experienced experimental stress conditions (isolation/restraint stress). Stress-1 group was stressed during the immunization period, while Stress-2 group was stressed during the local challenge period. Chamber exudates and serum were collected and analyzed for levels of anti-P. gingivalis antibodies (IgG, IgG1 and IgG2a). The levels of serum antibodies to P. gingivalis were not different between the three tested groups, excluding increased levels of IgG2a in Stress-1 group at baseline. The levels of antibodies in the chamber exudates were significantly lower in the stressed groups at baseline, but higher at d 7. The IgG1 to IgG2a ratio was significantly higher in the control group compared with the two stressed groups. The findings of the present study suggest that chronic psychological stress had a marked impact on the localized response to P. gingivalis challenge. The lower IgG1/IgG2a ratio observed in the stress groups suggests elevated Th1 response during stress.

Periodontitis modified by systemic factors

Microbial dental plaque is the initiator of periodontal disease but whether it affects a particular subject, what form the disease takes, and how it progresses, are all dependent on the host defenses to this challenge. Systemic factors modify all forms periodontitis principally through their effects on the normal immune and inflammatory defenses. Some good examples of this effect exist such as when there is a reduction in number or function of polymorphonuclear leukocytes (PMNs) that may result in an increased rate and severity of periodontal destruction. Many other systemic factors are much less clear cut and are difficult to causally link to periodontitis. In many cases the literature is insufficient to make definite statements on links between systemic factors and periodontitis. It is also at times difficult to be precise regarding the causative agent in systemic exposures such as smoking and even prescribed drug therapy. The possible role of systemic diseases and systemic exposures in initiating or modifying the progress of periodontal disease is clearly a complex issue. It is however generally agreed that several conditions may give rise to an increased prevalence, incidence, or severity of gingivitis and periodontitis. The categorization of the systemic modifying factors causing periodontitis and the evidence to support the role of these factors are the focus of this review. An attempt has been made to consider the conditions under broad headings, but it will be clear that many conditions fall within more than one category and that for several conditions only case reports exist whereas in other areas an extensive literature is present.