The Process of Acclimation to Chronic Hypoxia Leads to Submandibular Gland and Periodontal Alterations: An Insight on the Role of Inflammatory Mediators

A preliminary study of the salivary microbiota of young male subjects before, during, and after acute high-altitude exposure

Background

The microbial community structure in saliva differs at different altitudes. However, the impact of acute high-altitude exposure on the oral microbiota is unclear. This study explored the impact of acute high-altitude exposure on the salivary microbiome to establish a foundation for the future prevention of oral diseases. Methods. Unstimulated whole saliva samples were collected from 12 male subjects at the following three time points: one day before entering high altitude (an altitude of 350 m, pre-altitude group), seven days after arrival at high altitude (an altitude of 4,500 m, altitude group) and seven days after returning to low altitude (an altitude of 350 m, post-altitude group). Thus, a total of 36 saliva samples were obtained. 16S rRNA V3-V4 region amplicon sequencing was used to analyze the diversity and structure of the salivary microbial communities, and a network analysis was employed to investigate the relationships among salivary microorganisms. The function of these microorganisms was predicted with a Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis.

Results

In total, there were 756 operational taxonomic units (OTUs) identified, with 541, 613, and 615 OTUs identified in the pre-altitude, altitude, and post-altitude groups, respectively. Acute high-altitude exposure decreased the diversity of the salivary microbiome. Prior to acute high-altitude exposure, the microbiome mainly consisted of Proteobacteria, Firmicutes, Bacteroidetes, Fusobacteria, and Actinobacteria. After altitude exposure, the relative abundance of Streptococcus and Veillonella increased, and the relative abundance of Prevotella, Porphyromonas, and Alloprevotella decreased. The relationship among the salivary microorganisms was also affected by acute high-altitude exposure. The relative abundance of carbohydrate metabolism gene functions was upregulated, while the relative abundance of coenzyme and vitamin metabolism gene functions was downregulated.

Conclusion

Rapid high-altitude exposure decreased the biodiversity of the salivary microbiome, changing the community structure, symbiotic relationships among species, and abundance of functional genes. This suggests that the stress of acute high-altitude exposure influenced the stability of the salivary microbiome.

Impact of high altitude on composition and functional profiling of oral microbiome in Indian male population

The oral cavity of human contains bacteria that are critical for maintaining the homeostasis of the body. External stressors such as high altitude (HA) and low oxygen affect the human gut, skin and oral microbiome. However, compared to the human gut and skin microbiome, studies demonstrating the impact of altitude on human oral microbiota are currently scarce. Alterations in the oral microbiome have been reported to be associated with various periodontal diseases. In light of the increased occurrence of HA oral health related problems, the effect of HA on the oral salivary microbiome was investigated. We conducted a pilot study in 16 male subjects at two different heights i.e., H1 (210 m) and H2 (4420 m). Total of 31 saliva samples,16 at H1 and 15 at H2 were analyzed by utilizing the 16S rRNA high-throughput sequencing, to explore the relationship between the HA environment and salivary microbiota. The preliminary results suggesting that, the most abundant microbiome at the phylum level are: Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Interestingly, 11 genera were identified at the both heights with different relative abundances. In addition, the salivary microbiome was more diverse at H1 compared to H2 as demonstrated by decreased alpha diversity. Further, predicted functional results indicate that microbial metabolic profiles significantly decreased at H2 as compared to H1, including two major metabolic pathways involving carbohydrates, and amino acids. Our findings show that HA induces shifts in the composition and structure of human oral microbiota which can affect host health homeostasis.

Composition and regulation of the immune microenvironment of salivary gland in Sjögren’s syndrome

Primary Sjögren’s syndrome (pSS) is a systemic autoimmune disease characterized by exocrine gland dysfunction and inflammation. Patients often have dry mouth and dry eye symptoms, which seriously affect their lives. Improving dry mouth and eye symptoms has become a common demand from patients. For this reason, researchers have conducted many studies on external secretory glands. In this paper, we summarize recent studies on the salivary glands of pSS patients from the perspective of the immune microenvironment. These studies showed that hypoxia, senescence, and chronic inflammation are the essential characteristics of the salivary gland immune microenvironment. In the SG of pSS, genes related to lymphocyte chemotaxis, antigen presentation, and lymphocyte activation are upregulated. Interferon (IFN)-related genes, DNA methylation, sRNA downregulation, and mitochondrial-related differentially expressed genes are also involved in forming the immune microenvironment of pSS, while multiple signaling pathways are involved in regulation. We further elucidated the regulation of the salivary gland immune microenvironment in pSS and relevant, targeted treatments.

Mucus composition abnormalities in sinonasal mucosa of chronic rhinosinusitis with and without nasal polyps

Mucus secretion and its composition are vital in the maintenance of airway health, among which hypoxia-inducible factors (HIFs) are thought to be involved in the regulation of mucin synthesis and regulation. Nasal mucus composition difference between healthy individuals and chronic rhinosinusitis (CRS) patients may contribute to the pathology of chronic nasal diseases, but so far, their role has yet to be completely understood. Nasal biopsy specimens were obtained from 24 healthy subjects and 99 patients with CRS without (CRSsNP, n=36) or with (CRSwNP, n=63) nasal polyps. Immunohistochemical (IHC) and immunofluorescent (IF) staining, quantitative real-time PCR, and western blot were performed to compare the nasal mucus composition between the subjects. Areas of the serous gland and mucous gland were both significantly increased in CRSsNP patients. In CRSwNP patients, a decrease in submucosal gland density and a marked increase in goblet cells were observed. The major gel-forming mucins in the sinonasal mucosa of CRSsNP and CRSwNP are MUC5B and MUC5AC respectively. Mucous cells are found in a higher proportion in both CRSsNP and CRSwNP. The proportion of MUC5AC-positive goblet cells was increased in CRSwNP. The mRNA level of HIF-2α was significantly increased in CRS, and both HIF-1α and HIF-2α were expressed in serous cell but not mucous cell. Over secretion and altered composition of mucus are observed in sinonasal mucosa of CRS, which was mainly associated with glandular hyperplasia in CRSsNP and goblet cell hyperplasia in CRSwNP. Mucus abnormality compromised both non-specific and specific antimicrobial capabilities in the sinonasal mucosa. HIF expression may contribute to differences in mucin synthesis and serous gland regulation, which needs further investigation to understand the pathology of CRS.

The correlation of altitude with gingival status among adolescents in western China: a cross-sectional study

Periodontal disease is common in Chinese adolescents. There is little information about the effect of different altitudes on gingival health. This study aimed to investigate the gingival status at different altitudes and to identify relative factors that affect adolescents' gingival status. A total of 1033 adolescents aged 12-14 years were included in this cross-sectional study in Ganzi (plateau, 1400 m, 2560 m, 3300 m) and Suining (plain, 300 m). Gingival status was assessed by the presence of gingival bleeding on probing (BOP) and dental calculus (DC). Demographic variables, socioeconomic status, dairy habits and oral health-related knowledge, attitudes and behaviors were obtained via questionnaire. Univariate and multivariate binary logistic regression analyses were performed to identify potential relative factors. A total of 64.09% and 77.15% of adolescents had BOP and DC, respectively. The prevalence rates of BOP and DC were higher in the plateau than the plain (P < 0.05). After adjusting for all other factors and interaction terms, residence altitudes of 2560 m [300 m as reference: P < 0.001, odds ratio (OR) = 4.072] and 3300 m (300 m as reference: P = 0.002, OR = 4.053) were significant relative factors of BOP, and an altitude of 2560 m (300 m as reference: P = 0.001, OR = 3.866, 1400 m as reference: P = 0.001, OR = 3.944) was an important relative factor of DC. Gingival bleeding and calculus deposits were common at different altitudes. High altitude was a significant relative factor of gingival bleeding and calculus deposits.

High Altitude and Its Effects on Oral Health: A Review of Literature

Health deterioration at high altitudes is related to many pathophysiological processes. The literature contains much evidence describing the multiple factors responsible for this deterioration, including hypoxia, decreased oxygen saturation, and decreased barometric pressure. An increase in the levels of oxidative stress at high altitudes can lead to many serious health events, although the human body may be able to adapt to such changes in the case of people who are accustomed to living at a high altitude. The pathophysiological processes at high altitudes also have adverse effects on oral tissue health. The aim of this review is to summarize the major published findings about oral health deterioration of living in and travelling to high-altitude areas.

Most studies have noted the adverse effects of prolonged exposure to hypoxia at high altitudes on oral tissues, including the salivary gland, periodontal tissue, gingival crevicular fluids, and jawbone. These changes include increases in the levels of inflammatory mediators and periodontal inflammation parameters. In addition, the incidence and severity of dental fluorosis is higher in residents of high-altitude areas. Abrupt changes in barometric pressure in people who travel to high altitudes may cause dental barotrauma and appear to increase sensitivity to pain (barodontalgia). In conclusion, it is important to consider that travelling to and living in high-altitude areas is a possible risk factor for multiple oral diseases.

Lessons learned from proteome analysis of perinatal neurovascular pathologies

INTRODUCTION

Perinatal and pediatric diseases related to neurovascular disorders cause significant problems during life, affecting a population with a long life expectancy. Early diagnosis and assessment of the severity of these diseases are crucial to establish an appropriate neuroprotective treatment. Currently, physical examination, neuroimaging and clinical judgment are the main tools for diagnosis, although these tests have certain limitations. There is growing interest in the potential value of noninvasive biomarkers that can be used to monitor child patients at risk of brain damage, allowing accurate, and reproducible measurements.

AREAS COVERED

This review describes potential biomarkers for the diagnosis of perinatal neurovascular diseases and discusses the possibilities they open for the classification and treatment of neonatal neurovascular diseases.

EXPERT OPINION

Although high rates of ischemic and hemorrhagic stroke exist in pediatric populations, most studies have focused on biomarkers of hypoxic-ischemic encephalopathy. Inflammatory and neuronal biomarkers such as S-100B and GFAP, in combination with others yet to be discovered, could be considered as part of multiplex panels to diagnose these diseases and potentially for monitoring response to treatments. Ideally, noninvasive biofluids would be the best source for evaluating these biomarkers in proteomic assays in perinatal patients.

Mandibular biomechanical behavior of rats submitted to chronic intermittent or continuous hypoxia and periodontitis

BACKGROUND

The aim of this study was to investigate the effects of exposure to continuous (CH) and intermittent (IH) hypoxia on biomechanical properties of the mandible and periodontal tissue of animals submitted to experimental periodontitis (EP) when applying loads in a hypoxic environment.

METHODS

Adult female Wistar rats were exposed during 90 days to IH or CH (simulated high altitude of 4200 m above sea level). Fourteen days prior to the euthanasia, EP was induced to half of the animals of each group.

RESULTS

Only in the rats with EP, IH decreased the maximum capacity of the mandible to withstand load and the limit of elastic load. Indicators of intrinsic properties of the bone material were significantly reduced by both types of hypoxia in rats with EP. Hypoxia enhanced the alveolar bone loss induced by EP in the buccal side of the mandible, without showing additional effects in lingual or interradicular bone. Hypoxia increased prostaglandin E₂ content in gingival tissue of healthy animals and further elevated the E₂ levels increased by EP.

CONCLUSIONS

When periodontitis is present, hypoxic stress induces a decrease in mineral properties that ultimately affects the ability of the mandible to resist load, mainly during intermittent exposure to hypoxia. These effects on bone may be related to the higher levels of prostaglandin E₂ reached in the surrounding gingival tissue. The findings of this study may stimulate strategies to prevent unwanted effects of hypoxia on periodontal tissues.

Chronic Hypoxia-Induced Microvessel Proliferation and Basal Membrane Degradation in the Bone Marrow of Rats Regulated through the IL-6/JAK2/STAT3/MMP-9 Pathway

Chronic hypoxia (CH) is characterized by long-term hypoxia that is associated with microvessel proliferation and basal membrane (BM) degradation in tissues. The IL-6/JAK2/STAT3/MMP-9 pathway has been described in a variety of human cancers and plays an essential role in microvessel proliferation and BM degradation. Therefore, this study investigated the role of the IL-6/JAK2/STAT3/MMP-9 pathway in hypoxia-mediated microvessel proliferation and BM degradation in the rat bone marrow. Eighty pathogen-free Sprague Dawley male rats were randomly divided into four groups (20 per group)—control group, CH group (exposed to hypoxia in a hypobaric chamber at a simulated altitude of 5000 m for 28 d), CH + STAT3 inhibitor group (7.5 mg/kg/d), and CH + DMSO group. Microvessel density (MVD) and BM degradation in the bone marrow were determined by immunofluorescence staining and transmission electron microscopy. Serum IL-6 levels were assessed by enzyme-linked immunosorbent assay (ELISA), and the levels of P-JAK2, P-STAT3, and MMP-9 were assessed by western blot analysis and real-time reverse transcription PCR (RT-PCR). Hypoxia increased serum IL-6 levels, which in turn increased JAK2 and STAT3 phosphorylation, which subsequently upregulated MMP-9. Overexpression of MMP-9 significantly promoted the elevation of MVD and BM degradation. Inhibition of STAT3 using an inhibitor, SH-4-54, significantly downregulated MMP-9 expression and decreased MVD and BM degradation. Surprisingly, STAT3 inhibition also decreased serum IL-6 levels and JAK2 phosphorylation. Our results suggest that the IL-6/JAK2/STAT3/MMP-9 pathway might be related to CH-induced microvessel proliferation and BM degradation in the bone marrow.