Hypoxia‐induced endothelial cell responses – possible roles during periodontal disease

Abstract

Background and objective Inflammatory periodontal pockets are known to be hypoxic. Hypoxia influences vascular response to periodontal inflammation, including angiogenesis, which is critical for oxygen and nutrient delivery to periodontal tissues and granulation tissue formation. Our previous work suggests that periodontal bacteria may actively contribute to pocket hypoxia. Herein, we test the hypothesis that Fusobacterium nucleatum actively induces low oxygen tension, which modulates angiogenesis and endothelial cell activity. HUVEC cells were incubated in 1.5% oxygen for (Folkman & Shing, 1992)48 hours. Cell proliferation was measured by MTT; surface expression of CD31, CD34 and VEGF receptors (VEGFR1, VEGFR2) were analyzed by FACS. mRNA expression of HIF isoforms, iNOS, eNOS, COX‐2, and VEGF was measured by quantitative PCR. Supernatants were analyzed for the release of IL‐1α, TNF‐α, and VEGF by ELISA or multiplex immunoassays and nitric oxide was measured by colorimetric assay. F. nucleatum actively depleted oxygen. Hypoxia resulted in a significant increase of HIF isoforms. iNOS was increased while nitric oxide was unchanged. VEGF release was increased at 4 hours followed by an increase in VEGFR1 at 12 hours, but not VEGFR2. CD31 expression was reduced and CD34 was increased after 48 hours (p < 0.05). IL‐1α and TNF‐α release were decreased at 4 hours (p < 0.05), but both increased by 24 hours; TNF‐α increased at 24 h. The data highlight the role of hypoxia in endothelial cell inflammatory changes. F. nucleatum, considered a bridging species in the development of periodontopathic biofilms induces hypoxia in the periodontium leading to angiogenic changes in periodontal disease pathogenesis.

Pretreatment of ghrelin protects H9c2 cells against hypoxia/reoxygenation-induced cell death via PI3K/AKT and AMPK pathways

“…Previous studies have revealed hypoxia triggered a significant cell death by mediating iNOS/Cox-2 pathway [21][22][23]. Thus, we detected the expression changes of Cox-2 and iNOS in H9c2 cells following ghrelin pre-treatment and H/R.…”

Role and Regulation of Mechanotransductive HIF-1α Stabilisation in Periodontal Ligament Fibroblasts

“…During orthodontic tooth movement, pressure and tension zones develop in the periodontal ligament [ 3 ], resulting in reduced oxygen levels [ 2 ]. HIF-1α is the main transcriptional regulator during hypoxic conditions [ 10 , 11 ], regulating the transcription of hypoxia-inducible factors such as VEGF [ 24 , 25 ] or COX-2 [ 26 ]. Accordingly, we detected increased VEGF and COX-2 expression during pressure application, whereas only COX-2, not VEGF, was increased with tensile strain, which was previously shown in PDLF [ 6 , 27 ].…”

An immunofluorescence study on VEGF and extracellular matrix proteins in human periodontal ligament during tooth movement

“…The orthodontic forces during OTM are transmitted to endothelial cells, promoting the migration of leukocytes, which secrete many signalling molecules, such as cytokines, chemokines, and growth factors, as well as inflammatory mediators that stimulate PDL and alveolar bone to remodel the ECM (Di Domenico et al., 2012; Mendes et al., 2018).…”

“…Immediately after force application, the bloods vessels respond with increase of permeability. In this phase, it a decrease of CD31, an adhesion molecule on endothelial cells, occurs, suggesting an increased potential for vascular permeability (Mendes et al., 2018). During orthodontic therapy, biological activity is characterized by an increase in cellular response (Baumrind, 1969; Storey, 1973).…”