Role of calcineurin in Porphyromonas gingivalis-induced myocardial cell hypertrophy and apoptosis

Disruption of Histamine-H1R signaling exacerbates cardiac microthrombosis after periodontal disease via TLR4/NFκB-p65 pathway

Periodontal disease is a chronic inflammatory disease that is highly correlated with cardiovascular disease(CVD). Histamine has been proven to participate in the pathophysiological processes of cardiovascular disease and oral inflammation. However, the role of histamine in the development of cardiac microthrombosis caused by periodontal disease has not been fully elucidated. We established a murine periodontal inflammation model by injecting lipopolysaccharide (LPS) or Porphyromonas gingivalis (P. gingivalis). In order to examine the effect of histamine/H1R signaling on cardiac injury after periodontal disease, we used histidine decarboxylase- knockout (HDC-/-) mice and histamine 1 receptor (H1R) antagonist. Our results demonstrated that LPS-induced periodontal inflammation significantly increased CD11b+Gr-1+ neutrophils in the peripheral blood and myocardial interstitium. Histamine deficiency resulted in further increases in P. gingivalis, neutrophils, inflammatory cytokines, and cardiac microthrombosis in the myocardium of HDC-/- mice compared to wild-type (WT) mice. Mechanistic analysis showed that blocking H1R could synergistically interact with LPS, further increasing the phosphorylation of p65, exacerbating the inflammatory response of neutrophils and endothelial cell damage. Conclusively, the disruption of histamine-H1R signaling exacerbates cardiac microthrombosis after periodontal disease via TLR4/NFκB-p65 pathway. Our findings not only reveal a link between periodontal inflammation and myocardial injury but also provided some thoughts for the use of H1R antagonist in clinical practice.

A common oral pathogen Porphyromonas gingivalis induces myocarditis in rats

AIM

To evaluate whether Porphyromonas gingivalis (P. gingivalis) inoculation could induce cardiac remodelling in rats.

MATERIALS AND METHODS

The study was conducted on 33 Wistar rats, which were distributed in the following experimental groups: not inoculated; inoculated with 1 × 10⁸ CFU/ml of bacteria; inoculated with 3 × 10⁸ CFU/ml of bacteria. The animals were inoculated at baseline and on the 15th day of follow-up. Blood collection was performed at baseline and 60 min after each inoculation. At 29 days, the animals were subjected to echocardiography and at 30 days to haemodynamic studies before sacrificing them.

RESULTS

Impact of the bacteria was more evident in rats that received higher P. gingivalis concentration. Thus, 3 × 10⁸ CFU/ml of bacteria increased the rectal temperature and water content in the lung as well as myocardial necrosis and fibrosis. P. gingivalis induced the intensification of DNA fragmentation and increased the levels of malondialdehyde, oxidized proteins, and macrophage expression in the myocardium. These findings were associated with lower LV isovolumetric relaxation time, +dP/dt, -dP/dt, and higher end-diastolic pressure.

CONCLUSIONS

P. gingivalis bacteraemia is significantly associated with adverse cardiac remodelling and may play a biological role in the genesis of heart failure.

Calcium inhibitor inhibits high glucose‑induced hypertrophy of H9C2 cells

The aim of the present study was to explore whether the hypertrophy of H9C2 cardiomyocytes was induced by high glucose, to investigate whether the calcium channel inhibitor (Norvasc) could inhibit this process and to clarify the possible signaling pathways. The morphology of H9C2 cells was observed under an optical microscope, and the cell surface area was measured by Image Pro Plus 6.1 software. Furthermore, fluorescence spectrophotometry was used to detect intracellular calcium concentration ([Ca²⁺]i). ELISA was performed to detect calcineurin (CaN) activity; reverse transcription-quantitative PCR and western blotting were performed to detect the mRNA and protein expression levels of CaN Aβ subunit (CnAβ), nuclear factor of activated T cells 3 (NFAT3) and β type myosin heavy chain (β-MHC). Cell size was increased with the increase in glucose concentration of culture medium at 48 and 72 h, respectively, and decreased with the addition of Norvasc compared with those without Norvasc (P<0.05). There was no significant difference in cell size with the addition of Norvasc compared with cells cultured with 5 mM glucose (P>0.05). The average [Ca²⁺]i activity of single cells in the 48- and 72-h culture groups treated with 50 mM glucose was significantly higher than cells treated with 5 mM glucose (P<0.05); and the fluorescent value of average [Ca²⁺]i activity of single cells was lower, following the addition of Norvasc than that without Norvasc (P<0.05). CaN activity in the 48- and 72-h culture group treated with 50 mM glucose was markedly higher than that treated with 5 mM glucose, and the activity of CaN notably decreased with the addition of Norvasc compared with those without Norvasc. The mRNA and protein expression levels of CnAβ, NFAT3 and β-MHC in the 48- and 72-h culture groups treated with 50 mM glucose were all significantly higher than those treated with 5 mM glucose (P<0.05). The mRNA and protein expression of CnAβ, NFAT3 and β-MHC cultured with 50 mM glucose were significantly decreased following the addition of Norvasc (P<0.05). Thus, the calcium channel inhibitor Norvasc may inhibit high glucose-induced hypertrophy of H9C2 cardiomyocytes by inhibiting the Ca²⁺-CaN-NFAT3 signaling pathway.

Periodontal bacteria DNA findings in human cardiac tissue - Is there a link of periodontitis to heart valve disease?

BACKGROUND

The aim of the study was to detect periodontal pathogens DNA in atrial and myocardial tissue, and to investigate periodontal status and their connection to cardiac tissue inflammation.

METHODS

In 30 patients, biopsy samples were taken from the atrium (A) and the ventricle myocardium (M) during aortic valve surgery. The dental examination included the dental and periodontal status (PS) and a collection of a microbiological sample. The detection of 11 periodontal pathogens DNA in oral and heart samples was carried out using PCR. The heart samples were prepared for detecting the LPS-binding protein (LBP), and for inflammation scoring on immunohistochemistry (IHC), comprising macrophages (CD68), LPS-binding protein receptor (CD14), and LBP (big42).

RESULTS

28 (93%) patients showed moderate to severe periodontitis. The periodontal pathogens in the oral samples of all patients revealed a similar distribution (3-93%). To a lesser extent and with a different distribution, these bacteria DNA were also detected in atrium and myocardium (3-27%). The LBP was detected in higher amount in atrium (0.22±0.16) versus myocardium (0.13±0.13, p=0.001). IHC showed a higher inflammation score in atrial than myocardial tissue as well as for CD14, CD68 and for LBP. Additional, periodontal findings showed a significant correlation to CD14 and CD68.

CONCLUSION

The results provide evidence of the occurrence of oral bacteria DNA at the cardiac tissue, with a different impact on atrial and myocardial tissue inflammation. Influence of periodontal findings was identified, but their relevance is not yet distinct. Therefore further clinical investigations with long term implication are warranted.

Over-expression of HO-1 on mesenchymal stem cells promotes angiogenesis and improves myocardial function in infarcted myocardium

Heme oxygenase-1 (HO-1) is a stress-inducible enzyme with diverse cytoprotective effects, and reported to have an important role in angiogenesis recently. Here we investigated whether HO-1 transduced by mesenchymal stem cells (MSCs) can induce angiogenic effects in infarcted myocardium. HO-1 was transfected into cultured MSCs using an adenoviral vector. 1 × 10⁶ Ad-HO-1-transfected MSCs (HO-1-MSCs) or Ad-Null-transfected MSCs (Null-MSCs) or PBS was respectively injected into rat hearts intramyocardially at 1 h post-myocardial infarction. The results showed that HO-1-MSCs were able to induce stable expression of HO-1 in vitro and in vivo. The capillary density and expression of angiogenic growth factors, VEGF and FGF2 were significantly enhanced in HO-1-MSCs-treated hearts compared with Null-MSCs-treated and PBS-treated hearts. However, the angiogenic effects of HO-1 were abolished by treating the animals with HO inhibitor, zinc protoporphyrin. The myocardial apoptosis was marked reduced with significantly reduced fibrotic area in HO-1-MSCs-treated hearts; Furthermore, the cardiac function and remodeling were also significantly improved in HO-1-MSCs-treated hearts. Our current findings support the premise that HO-1 transduced by MSCs can induce angiogenic effects and improve heart function after acute myocardial infarction.

P38 mitogen-activated protein kinase pathways are involved in the hypertrophy and apoptosis of cardiomyocytes induced by Porphyromonas gingivalis conditioned medium

The surrounding medium of periodontal pathogen Porphyromonas gingivalis (P. gingivalis) increased cardiomyocyte hypertrophy and apoptosis whereas Actinobaeillus actinomycetemcomitans and Prevotella intermedia had no effects. The purpose of this study is to clarify the role of p38 pathway in P. gingivalis conditioned medium-induced H9c2 myocardial cell hypertrophy and apoptosis. DNA fragmentation, cellular morphology, nuclear condensation, p38 protein products, and mitochondrial-dependent apoptotic related proteins in cultured H9c2 myocardial cell were measured by agarose gel electrophoresis, immunofluorescence, DAPI, and western blotting following P. gingivalis conditioned medium and/or pre-administration of SB203580 (p38 inhibitor). The p38 protein products and associated activities in H9c2 cells were both upregulated by P. gingivalis conditioned medium. P. gingivalis conditioned medium increased cellular sizes, DNA fragmentation, nuclear condensation, mitochondrial Bcl2-associated death promoter (Bad), cytosolic cytochrome c (cyt c), and the activated form of caspase-9 proteins in H9c2 cells. The increased cellular sizes, DNA fragmentation, nuclear condensation, Bad, cyt c, and caspase-9 activities of H9c2 cells treated with P. gingivalis conditioned medium were all significantly reduced after pre-administration of SB203580. Our findings suggest that the activity of p38 signal pathway may be initiated by P. gingivalis conditioned medium and further activate mitochondrial-dependent apoptotic pathways leading to cell death in cultured H9c2 myocardial cells.

Gingipain-dependent interactions with the host are important for survival of Porphyromonas gingivalis

Porphyromonas gingivalis, a major periodontal pathogen, must acquire nutrients from host derived substrates, overcome oxidative stress and subvert the immune system. These activities can be coordinated via the gingipains which represent the most significant virulence factor produced by this organism. In the context of our contribution to this field, we will review the current understanding of gingipain biogenesis, glycosylation, and regulation, as well as discuss their role in oxidative stress resistance and apoptosis. We can postulate a model, in which gingipains may be part of the mechanism for P. gingivalis virulence.