Polyamines found in gingival fluid enhance the secretory and oxidative function of human polymorphonuclear leukocytes in vitro

Gingival fibroblasts dynamically reprogram cellular metabolism during infection of Porphyromonas gingivalis

OBJECTIVE

The purpose of the present study was to explore the sequential changes in the cellular metabolism in gingival fibroblasts (GFs) in response toPorphyromonas gingvalis (P. gingivalis) ATCC33277 infection.

DESIGN

GFs were treated withP. gingivalis at the MOI of 50 for 4, 24 and 48 h to mimic the early, medium, and late phase in the bacterial infection. LDH assay and cell counting kit-8 were utilized to explore cell death and proliferation. Real-time PCR was utilized to explore the gene transcription of pro-inflammatory genes. The relative levels of biomolecules in GFs were measured by gas chromatography-mass spectrometry. Principal component analysis and orthogonal partial least-squares-discriminant analysis were performed to visualize the metabolic difference among experimental groups. In addition, pathway analysis was conducted regarding differential metabolites in GFs.

RESULTS

P. gingivalis infection triggered significant gene transcription of IL-1β, IL 6, MCP 1, and MMP 1 in GFs. In addition, P. gingivalis stimulated cell proliferation of GFs at MOI of 10, 50 and 250. Moreover, P. gingivalis triggered significant cell death at higher MOI. 69, 173 and 148 metabolites were qualitatively detected at 4, 24 and 48 h after P. gingivalis infection respectively in GFs, showing a sequential change of different phase. Kyoto Encyclopedia of Genes and Genomes pathway analysis demonstrated that ATP-binding cassette transporters, glutathione, purine and pyrimidine metabolism was significantly altered in different phase.

CONCLUSIONS

Human GFs may sequentially rewire metabolomics to shape the inflammatory responses and support the proliferation of host cells during P. gingivalis infection.

Pulmonary Surfactant Promotes Virulence Gene Expression and Biofilm Formation in Klebsiella pneumoniae

The interactions between Klebsiella pneumoniae and the host environment at the site of infection are largely unknown. Pulmonary surfactant serves as an initial point of contact for inhaled bacteria entering the lung and is thought to contain molecular cues that aid colonization and pathogenesis. To gain insight into this ecological transition, we characterized the transcriptional response of K. pneumoniae MGH 78578 to purified pulmonary surfactant. This work revealed changes within the K. pneumoniae transcriptome that likely contribute to host colonization, adaptation, and virulence in vivo Notable transcripts expressed under these conditions include genes involved in capsule synthesis, lipopolysaccharide modification, antibiotic resistance, biofilm formation, and metabolism. In addition, we tested the contributions of other surfactant-induced transcripts to K. pneumoniae survival using engineered isogenic KPPR1 deletion strains in a murine model of acute pneumonia. In these infection studies, we identified the MdtJI polyamine efflux pump and the ProU glycine betaine ABC transporter to be significant mediators of K. pneumoniae survival within the lung and confirmed previous evidence for the importance of de novo leucine synthesis to bacterial survival during infection. Finally, we determined that pulmonary surfactant promoted type 3 fimbria-mediated biofilm formation in K. pneumoniae and identified two surfactant constituents, phosphatidylcholine and cholesterol, that drive this response. This study provides novel insight into the interactions occurring between K. pneumoniae and the host at an important infection site and demonstrates the utility of purified lung surfactant preparations for dissecting host-lung pathogen interactions in vitro.

Disease Severity and Immune Activity Relate to Distinct Interkingdom Gut Microbiome States in Ethnically Distinct Ulcerative Colitis Patients

Significant gut microbiota heterogeneity exists among ulcerative colitis (UC) patients, though the clinical implications of this variance are unknown. We hypothesized that ethnically distinct UC patients exhibit discrete gut microbiotas with unique metabolic programming that differentially influence immune activity and clinical status. Using parallel 16S rRNA and internal transcribed spacer 2 sequencing of fecal samples (UC, 30; healthy, 13), we corroborated previous observations of UC-associated bacterial diversity depletion and demonstrated significant Saccharomycetales expansion as characteristic of UC gut dysbiosis. Furthermore, we identified four distinct microbial community states (MCSs) within our cohort, confirmed their existence in an independent UC cohort, and demonstrated their coassociation with both patient ethnicity and disease severity. Each MCS was uniquely enriched for specific amino acid, carbohydrate, and lipid metabolism pathways and exhibited significant luminal enrichment of the metabolic products of these pathways. Using a novel ex vivo human dendritic cell and T-cell coculture assay, we showed that exposure to fecal water from UC patients caused significant Th2 skewing in CD4⁺ T-cell populations compared to that of healthy participants. In addition, fecal water from patients in whom their MCS was associated with the highest level of disease severity induced the most dramatic Th2 skewing. Combined with future investigations, these observations could lead to the identification of highly resolved UC subsets based on defined microbial gradients or discrete microbial features that may be exploited for the development of novel, more effective therapies.

Despite years of research, the etiology of UC remains enigmatic. Diagnosis is difficult and the patient population heterogeneous, which represents a significant barrier to the development of more effective, tailored therapy. In this study, we demonstrate the clinical utility of the gut microbiome in stratifying UC patients by identifying the existence of four distinct interkingdom pathogenic microbiotas within the UC patient population that are compositionally and metabolically distinct, covary with clinical markers of disease severity, and drive discrete CD4⁺ T-cell expansions ex vivo. These findings offer new insight into the potential value of the gut microbiome as a tool for subdividing UC patients, opening avenues to the development of more personalized treatment plans and targeted therapies.

Exogenous factors in the immunotoxicity of oral PMN

Current evidence indicates that periodontal disease is frequently due to inappropriate levels of gingival granulocyte functions. Reason of this failure may be the toxic effects of a number of local or systemic exogenous factors, capable of spreading through the gingival crevice environment, and strongly conditioning the granulocyte activities. The wide list includes bacteria and granulotoxic products, hedonistic drugs (mainly tobacco), and chemotherapeutic agents (especially antimicrobials used for preventing or reducing the accumulation of dental plaque). Almost always, their presence induces a time- and/or dose-dependent toxicity.

Nitric oxide and polyamine pathway-dependent modulation of neutrophil free amino- and α-keto acid profiles or host defense capability

We have examined the effects of N(omega)-nitro-L-arginine-methylester-hydrochloride [L-NAME; inhibitor of nitric oxide synthase], S-nitroso-N-acetyl-penicillamine [SNAP; nitric oxide donor], alpha-difluoro-methyl-ornithine [DFMO; inhibitor of ornithine decarboxylase] arginine or ornithine as well as the combination of arginine or ornithine with L-NAME, SNAP or DFMO on intracellular free amino- and alpha-keto acid profiles and the immune function markers superoxide anion and hydrogen peroxide generation as well as released myeloperoxidase activity in neutrophils (PMN). Although the underlying mechanisms still remain unclear, we believe from our results that nitric oxide as well as polyamine-dependent pathways are involved in the signal transmission of free radical molecule, beneficial nutritional therapy or maleficient pharmacological stress-induced alterations in PMN nutrient composition. Relevant changes in intragranulocyte free amino- and alpha-keto acid homeostasis and metabolism, especially, may be one of the determinants in PMN nutrition that positively or negatively influences and modulate neutrophil host defence capability and immunocompetence.

In vitro effects of polyamines on polymorphonuclear cell apoptosis and implications in the pathogenesis of periodontal disease

Apoptosis provides a mechanism for clearance of unwanted cells in a variety of situations in which programmed or physiological cell death occurs; but the premature death of defensive cells could promote infection, inflammation and concomitant diseases. Polymorphonuclear cells (PMN) of gingival sulcus play an important role in host defense against periodontal tissue-invading bacteria, but their phagocytic activity is conditioned by several virulence factors released by oral pathogens. Polyamines derived from oral bacteria frequently occur at concentrations approaching 1 mM in gingival fluid at diseased periodontal sites. Brief exposure of PMN to polyamines shortened the lag culture time required to observe microscopical or DNA fragmentation traces. Increase of Fas/Apo-1 expression and caspase-8 and caspase-3 activation focused two typical steps in the pathway of the pro-apoptotic mechanism exhibited by polyamines, even if to a different extent: spermine > spermidine > putrescine. The possible role played by polyamines in the pathogenesis of periodontal disease by dysregulating apoptosis of gingival PMN is discussed.

Inhibitory effects of protamines on proteolytic and adhesive activities of Porphyromonas gingivalis

Protamines (salmine prepared from sperm DNA of salmon and clupeine from herring sperm), which are basic peptides rich in arginine, were found to inhibit the proteolytic activity of arginine-specific cysteine protease (RC-protease) from Porphyromonas gingivalis. Lineweaver-Burk plot analysis revealed that the protamines competitively inhibited proteolytic activity with cleavage of benzoyl-L-arginine-p-nitroanilide, a synthetic substrate of RC-protease. Furthermore, the protamines were capable of binding strongly to P. gingivalis fimbriae and inhibited fimbrial interaction with immobilized fibronectin. These results clearly show that protamines are potent inhibitors of the proteolytic and adhesive activities of P. gingivalis.

Transplantation, not dialysis, corrects azotemia-dependent priming of the neutrophil oxidative burst

The oxidative burst of neutrophils from patients with renal failure before the initiation of dialysis is primed for an enhanced response after stimulation by phagocytosis or chemoattractants. This study shows that phagocytosis-stimulated oxidative burst activity remains primed in patients treated with both high-efficiency hemodialysis and continuous ambulatory peritoneal dialysis (CAPD), but it is normal in patients with a functioning renal transplant. Incubation of normal neutrophils or HL-60 granulocytes in azotemic plasma results in increased resting and phagocytosis-stimulated H2O2 production, which is rapidly reversible on removal of the plasma. Priming of the oxidative burst by azotemic plasma is independent of changes in opsonization and phagocytosis and does not require protein synthesis. These results suggest that azotemic plasma contains a substance or substances capable of reversibly priming oxidative burst activity in neutrophils and neutrophil-like cell lines. The Inability of high-efficiency hemodialysis and CAPD to normalize oxidative burst activity suggests that this substance is of higher molecular weight.

Polyamines found in the inflamed periodontium inhibit priming and apoptosis in human polymorphonuclear leukocytes

BACKGROUND

Polymorphonuclear leukocytes (PMNs) are exposed to high concentrations of polyamines in the inflamed periodontium and possess a transport system for taking up these compounds. Previous studies suggest that polyamines are involved in priming of the PMN respiratory burst by tumor necrosis factor-alpha (TNF-alpha) and can stabilize DNA against degradation. The purpose of this study was to determine whether exogenous polyamines can modulate priming by TNF-alpha or delay nuclear changes associated with PMN apoptosis (programmed cell death).

METHODS

Isolated human PMNs were incubated with putrescine or spermidine in vitro. Superoxide generation was measured with a cytochrome C reduction assay, and apoptotic changes were assessed by fluorescence microscopy (after cell staining with acridine orange and ethidium bromide).

RESULTS

Incubation with 1 mM putrescine for 1 hour inhibited superoxide production by TNF-primed PMNs by 20%, but enhanced the production of superoxide by unprimed cells by 38%. Both effects were dose dependent and statistically significant (P <0.03, repeated measures ANOVA and Dunnett's test). Spermidine had no significant effects on PMN oxidative function. With regard to apoptosis, 1 mM putrescine or spermidine produced a statistically significant reduction in the proportion of apoptotic PMNs within 6 to 9 hours (P <0.05). In cells incubated for 7 hours with 300 microM putrescine or spermidine, the proportion of apoptotic cells was approximately 30% lower than in untreated controls (P <0.05, Dunnett's test). The delay of apoptosis by spermidine was less profound than that produced by TNF-alpha and was not additive to the effects of this cytokine.

CONCLUSIONS

Polyamines could potentially impair the priming of PMN oxidative function by TNF-alpha at sites where this cytokine is present. In the absence of TNF-alpha, polyamines could enhance PMN superoxide release and enhance the maintenance of PMN function in the periodontal pocket.

Ochratoxicosis: prevention of developmental toxicity by L-methionine in rats

L-Methionine was found to inhibit the developmental toxicity induced by ochratoxin A (OA) in pregnant female rats. The fetuses had significantly lower weights. Dams and fetuses treated with OA had visceral and skeletal anomalies, while combined treatment with L-methionine and OA showed no significant changes when compared to the control. Histopathological examinations revealed that OA caused alterations in liver, kidney and vagina of pregnant rats, whereas methionine supplementation provided partial protection for renal and liver tissue.

Polyamines found in gingival fluid inhibit chemotaxis by human polymorphonuclear leukocytes in vitro

Putrescine and spermidine occur at concentrations approaching 1 mM in gingival fluid at diseased periodontal sites. Previous work demonstrates that these polyamines potentiate Ca2+ signaling in polymorphonuclear leukocytes (PMNs), resulting in enhanced degranulation and superoxide generation. The present study extends this work by characterizing the effects of polyamines on PMN chemotaxis and phagocytosis, in which Ca2+ signaling plays a less defined regulatory role. Putrescine (1 mM) and spermidine (0.1 to 0.5 mM) significantly inhibited chemotaxis to fMet-Leu-Phe and C5a (P < 0.05). This inhibition was not strongly related to any effect polyamines have on PMN adhesion, actin polymerization, or formyl peptide receptor expression. Neither putrescine nor spermidine had a significant impact on phagocytosis of opsonized bacteria by PMNs. Thus, at concentrations similar to those found in gingival fluid, polyamines could potentially inhibit recruitment of PMNs to diseased pockets without impairing their ability to engulf invading bacteria.