Induction of periodontitis and oral microbiome dysbiosis in a mouse model with heart failure with preserved ejection fraction results in worsening hypertension and diastolic dysfunction

Introduction

Heart Failure with Preserved Ejection Fraction (HFpEF) is characterized by increased inflammation and disruption of the nitric oxide (NO) pathway. Oral microbiota has an essential role in the generation of a large portion of the NO bioavailability pool in the human body. Periodontitis (PD) is a common inflammatory condition that contributes to the development of chronic low-grade inflammation, oral microbiota dysbiosis, and dysregulation of the NO hemostasis.

Purpose

In this study, we sought to investigate the direct effect of PD induction on HFpEF manifestation in a mouse model.

Methods

HFpEF was induced in 11-week-old C57/black male mice by high-fat diet and inhibition of NO synthase using L-NAME (Nω-nitro-l-arginine-methyl-ester) (a “2-hit-model”) for 10 weeks. PD was induced by oral infection with P. gingivalis. Diastolic function of the left ventricle (LV) was assessed by high-frequency echocardiography. Blood pressure (BP) was measured using CODA non-invasive tail-cuff system.

Results

Induction of PD resulted in a significantly impaired diastolic function demonstrated by more pronounced decrease in e' and increase in E/e' ratio compared to HFpEF without PD or control mice (E/e': 39.7±2.6 vs. 30.1±1.9 vs. 24.3±2.1 for PD-HFpEF [n=15], HFpEF [n=15], and controls [n=10], respectively, p<0.001). While LV ejection fraction (EF) was similar, global longitudinal strain (GLS) was decreased in the HFpEF group and further decreased in the PD-HFpEF group compared to controls (p<0.001). BP was elevated in the HFpEF mice and PD induction resulted in a more remarkable increase in BP (systolic BP: 124.7±3.3 vs. 112.7±3.8 vs. 94.8±2.2 mmHg, respectively, p<0.001).

Conclusions

Induction of PD in a mouse model with HFpEF results in a more pronounced BP elevation and diastolic dysfunction compared to HFpEF without PD. Extensive molecular experiments are ongoing to explore the mechanisms responsible for the increased HFpEF severity in the setting of PD.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Israel Science Foundation

Amyloidosis of the aortic valve in patients with degenerative and bicuspid aortic stenosis

Introduction

Aortic stenosis (AS) is a common valvular disease, resulting in substantial morbidity and mortality. In younger patients, AS may occur as part of the bicuspid aortic valve (BAV) syndrome. Transthyretin cardiac amyloidosis (ATTR-CA) is an infiltrative disorder caused by the extracellular deposition of insoluble amyloid-derived fibrils. Recent studies have shown the presence of ATTR-CA in 4%-29% of degenerative AS patients. We hypothesized that amyloidosis may be involved in valve injury leading to AS.

Material and methods

We studied the aortic valves of 124 patients who underwent surgical aortic valve replacement at our institution over the last decade, included in our cardiosurgical database. Valves from 86 degenerative AS patients were compared to a control group of 38 patients with BAV stenosis. Patients with pure aortic regurgitation, history of rheumatic disease, or severe renal disease were excluded. The slides were stained with Congo red, and Thioflavin S then examined with regular, fluorescence and polarized light microscopy.

Results

In the degenerative AS group, Congo red and Thioflavin S staining was positive in 63% of the valves and 37% negative. The bicuspid AS group showed 68% positive and 32% negative for the Congo Red and Thioflavin S stains.

Discussion and conclusion

Our results indicate the presence of valvular amyloidosis in patients with AS, whether due to degenerative or congenital etiologies. This corroborates several recent studies. Intriguingly, there was an equally positive Congo red and Thioflavin S signal in bicuspid aortic valves. We speculate that the positive staining in the BAV group may indicate an inflammatory process associated with valve pathology inducing the accumulation of amyloid, and thus may not be transthyretin, as we expect in the experimental group. Another explanation may be that amyloidosis may be an epiphenomenon of valve “wear and tear” and not related to the pathogenesis in either etiology. Specific TTR immunofluorescence is underway to elucidate this question.

Funding Acknowledgement

Type of funding sources: None.

Alterations in the gut microbiota composition in the obesity phenotype of heart failure with preserved ejection fraction

Introduction

Obesity is one of the most common phenotypes of heart failure with preserved ejection fraction (HFpEF). A growing body of evidence indicates that obesity is characterized by compositional alterations in the intestinal microbiota and its metabolites, collectively referred as dysbiosis.

Purpose

We sought to investigate whether the obese phenotype of HFpEF is mediated by further alterations in the microbiota and whether gut dysbiosis fuels metabolic inflammation leading to progression of HFpEF.

Methods

HFpEF was induced in C57/black mice by high-fat diet and inhibition of NO synthesis (a “2-hit-model”) (Figure 1A). High-frequency echocardiography was performed to assess diastolic function. Blood pressure (BP) was measured using CODA non-invasive tail-cuff system. For human studies, patients with obese HFpEF as well as obese and non-obese healthy individuals were prospectively recruited. Gut microbial DNA was subjected to 16S ribosomal RNA gene sequencing, and the differences in abundance and composition of bacteria were defined both in humans and mice.

Results

In mice, the 2-hit model demonstrated significantly increased BP and impaired diastolic function in the obese HFpEF group (Figure 1B). Microbiome analysis showed significant differences in the gut microbial diversity and composition in the obese HFpEF compared to the non-HFpEF obese and chow-fed mice (Figure 1C). Similarly, human microbiome sequencing showed significant gut bacterial alterations in the diversity and composition of bacteria with more profound dysbiosis observed in the obese HFpEF patients compared to the obese and lean healthy individuals (Figure 1D).

Conclusions

We provide evidence in humans as well as in a murine animal model that the obese HFpEF phenotype is associated with more pronounced gut dysbiosis compared to the non-HFpEF obesity state. Further research will elucidate the causative link between gut dysbiosis and HFpEF manifestation and the mechanistic insights into the implication of gut microbiota in HFpEF progression.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Israel science foundation

Neural mechanisms underlying stress resilience in Ahi1 knockout mice: relevance to neuropsychiatric disorders

The Abelson helper integration site 1 (AHI1) gene has a pivotal role in brain development. Studies by our group and others have demonstrated association of AHI1 with schizophrenia and autism. To elucidate the mechanism whereby alteration in AHI1 expression may be implicated in the pathogenesis of neuropsychiatric disorders, we studied Ahi1 heterozygous knockout (Ahi1(+/-)) mice. Although their performance was not different from wild-type mice on tests that model classical schizophrenia-related endophenotypes, Ahi1(+/-) mice displayed an anxiolytic-like phenotype across different converging modalities. Using behavioral paradigms that involve exposure to environmental and social stress, significantly decreased anxiety was evident in the open field, elevated plus maze and dark-light box, as well as during social interaction in pairs. Assessment of core temperature and corticosterone secretion revealed a significantly blunted response of the autonomic nervous system and the hypothalamic-pituitary-adrenal axis in Ahi1(+/-) mice exposed to environmental and visceral stress. However, response to centrally acting anxiogenic compounds was intact. On resting-state functional MRI, connectivity of the amygdala with other brain regions involved in processing of anxiogenic stimuli and inhibitory avoidance learning, such as the lateral entorhinal cortex, ventral hippocampus and ventral tegmental area, was significantly reduced in the mutant mice. Taken together, our data link Ahi1 under-expression with a defect in the process of threat detection. Alternatively, the results could be interpreted as representing an anxiety-related endophenotype, possibly granting the Ahi1(+/-) mouse relative resilience to various types of stress. The current knockout model highlights the contribution of translational approaches to understanding the genetic basis of emotional regulation and its associated neurocircuitry, with possible relevance to neuropsychiatric disorders.

Cell death in cultured human Saos2 osteoblasts exposed to low-density lipoprotein

Osteoporosis (OP) and atherosclerotic-cardiovascular diseases (and possibly dementia) constitute emerging age-related co-morbidity states that might share risk factors. Blood-born lipids, like LDL involved in atherosclerosis and apolipoprotein-E4 (ApoE4) involved in dementia, may also be implicated in development of OP. We examined osteoblast cell lines as a culture model for OP by exposure to lipoproteins. ApoE expression in Saos2 and U2OS osteoblasts was confirmed by PCR. ApoE4 did decrease cell counts relatively to ApoE3, especially in Saos2 cells in which it was less selective for cells with higher alkaline phosphatase (ALP, an osteoblast marker) activity than ApoE3. This associates with ApoE4, being a risk factor for both dementia and OP. Saos2, but not U2OS, showed a decrease in cell counts after 48 h exposure to native LDL (NLDL). Both cell lines had decreased cell counts already after 24 h when exposed to oxidized-LDL (OxLDL) for which Saos2 also showed a higher sensitivity than U2OS. Exposure of Saos2 to both, OxLDL at low concentration (5 microg/ml) and NLDL revealed a shrunken size cell fraction of 17-23% on the fluorescence-activated cell sorter (FACS) analysis. Such shrunken cell fraction was not seen when Saos2 cells were exposed to 50 microg/ml of OxLDL or to OxLDL combined with 10 nM dexamethasone (DEX, a stimulator of osteoprogenitor differentiation). DEX treatment has lysed the cells earlier than 24 h post exposure and has selected more resistant cells that did not show apoptotic shrinkage in the FACS analysis done after 24 h. We interpret this as a failure to detect the apoptotic cell fraction due to their lysis prior to the FACS analysis. Western blots performed at different time points (10 min, 30 min, 4 h, 24 h, and 48 h) under OxLDL + DEX revealed a fall in the positive regulator of pp60Src-kinase phosphotyrosine (pY)418 relative to the DEX controls during the first 4 h. This is consistent with DEX osteogenic induction, known to be negatively regulated by c-Src, although the pY418/pY529 ratios (negative/positive kinase regulation) fell only at the 10 min time point. Contrarily the pY418/pY529 ratio increased, relative to untreated controls, under 5 microg/ml and 50 microg/ml of NLDL at the 4 h time point and under 50 microg/ml NLDL only at the 10 min time point, being consistent with the ability of a higher dose of LDL to antagonize osteoblast differentiation. This could be even more acceptable if the NLDL would have become minimally oxidized during its long purification procedure. Under NLDL, the Bcl-2/Bax ratio was pro-apoptotic at 10 min, 30 min, and 4 h only under 50 microg/ml, whereas under OxLDL + DEX it was pro-apoptotic only after 4 h suggesting that additional pathways contribute to cell death. These results indicate that lipid effects on human osteoblast lines in culture may be used as a model to identify molecular targets shared between OP and atherosclerosis for intervention in this co-morbidity.

Expression of the familial Mediterranean fever gene and activity of the C5a inhibitor in human primary fibroblast cultures

Familial Mediterranean fever (FMF) is an inherited disease whose manifestations are acute but reversible attacks of sterile inflammation affecting synovial and serosal spaces. The FMF gene (MEFV) was recently cloned, and it codes for a protein (pyrin/marenostrin) homologous to known nuclear factors. We previously reported the deficient activity of a C5a/interleukin (IL)-8 inhibitor, a physiologic regulator of inflammatory processes, in FMF serosal and synovial fluids. We now describe the concomitant expression of MEFV and C5a/IL-8-inhibitor activity in primary cultures of human fibroblasts. Fibroblasts grown from synovial and peritoneal tissues displayed C5a/IL-8-inhibitor activity that could be further induced with phorbol myristate acetate (PMA) and IL-1 beta. Very low levels of chemotactic inhibitor were evident in skin fibroblast cultures or in peritoneal and skin fibroblasts obtained from FMF patients. MEFV was expressed in peritoneal and skin fibroblasts at a lower level than in neutrophils and could be further induced by PMA and IL-1 beta. In the FMF cultures, the MEFV transcript carried the M694V mutation, consistent with the genetic defect found in patients with this disease. MEFV was also expressed in other cell lines that do not produce C5a/IL-8 inhibitor. These findings suggest that human primary fibroblast cultures express MEFV and produce C5a/IL-8-inhibitor activity. The interrelationship between pyrin, the MEFV product, and the C5a/IL-8 inhibitor requires further investigation. (Blood. 2000;96:727-731)