Brain-derived neurotrophic factor prevents the endothelial barrier dysfunction induced by interleukin-1β and tumor necrosis factor-α

Periodontal tissue regeneration with cementogenesis after application of brain-derived neurotrophic factor in 3-wall inflamed intra-bony defect

OBJECTIVE

The purpose of this study is to investigate regenerative process by immunohistochemical analysis and evaluate periodontal tissue regeneration following a topical application of BDNF to inflamed 3-wall intra-bony defects.

BACKGROUND

Brain-derived neurotrophic factor (BDNF) plays a role in the survival and differentiation of central and peripheral neurons. BDNF can regulate the functions of non-neural cells, osteoblasts, periodontal ligament cells, endothelial cells, as well as neural cells. Our previous study showed that a topical application of BDNF enhances periodontal tissue regeneration in experimental periodontal defects of dog and that BDNF stimulates the expression of bone (cementum)-related proteins and proliferation of human periodontal ligament cells.

METHODS

Six weeks after extraction of mandibular first and third premolars, 3-wall intra-bony defects were created in mandibular second and fourth premolars of beagle dogs. Impression material was placed in all of the artificial defects to induce inflammation. Two weeks after the first operation, BDNF (25 and 50 μg/mL) immersed into atelocollagen sponge was applied to the defects. As a control, only atelocollagen sponge immersed in saline was applied. Two and four weeks after the BDNF application, morphometric analysis was performed. Localizations of osteopontin (OPN) and proliferating cell nuclear antigen (PCNA)-positive cells were evaluated by immunohistochemical analysis.

RESULTS

Two weeks after application of BDNF, periodontal tissue was partially regenerated. Immunohistochemical analyses revealed that cells on the denuded root surface were positive with OPN and PCNA. PCNA-positive cells were also detected in the soft connective tissue of regenerating periodontal tissue. Four weeks after application of BDNF, the periodontal defects were regenerated with cementum, periodontal ligament, and alveolar bone. Along the root surface, abundant OPN-positive cells were observed. Morphometric analyses revealed that percentage of new cementum length and percentage of new bone area of experimental groups were higher than control group and dose-dependently increased.

CONCLUSION

These findings suggest that BDNF could induce cementum regeneration in early regenerative phase by stimulating proliferation of periodontal ligament cells and differentiation into periodontal tissue cells, resulting in enhancement of periodontal tissue regeneration in inflamed 3-wall intra-bony defects.

MiR-146a encapsulated liposomes reduce vascular inflammatory responses through decrease of ICAM-1 expression, macrophage activation, and foam cell formation

Vascular insults can create an inflammatory cascade involving endothelial cell, smooth muscle cell, and macrophage activation which can eventually lead to vascular disease such as atherosclerosis. Several studies have identified microRNA 146a's (miR-146a) anti-inflammatory potential based on its role in regulating the nuclear factor kappa beta (NF-κβ) pathway. Therefore, in this study, we introduced exogenous miR-146a encapsulated by liposomes to lipopolysaccharide (LPS) stimulated vascular cells and macrophages to reduce inflammatory responses. First, the miR-146a encapsulated liposomes showed uniform size (radius 96.4 ± 4.22 nm) and round shape, long term stability (at least two months), high encapsulation efficiency (69.73 ± 0.07%), and were well transfected to human aortic endothelial cells (HAECs), human aortic smooth muscle cells (SMCs), and human differentiated monocytes (U937 cells). In addition, we demonstrated that miR-146a encapsulated liposomes reduced vascular inflammation responses in HAECs and SMCs through inhibition of ICAM-1 expression and decreased monocyte adhesion. In macrophages, miR-146a liposome treatment demonstrated decreased production of proinflammatory cytokines, tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β), as well as reduced oxidized low-density lipoprotein (ox-LDL) uptake and foam cell formation. Thus, based on these results, miR-146a encapsulated liposomes may be promising for reducing vascular inflammation by targeting its multiple associated mediators.

Crosstalk Among NLRP3 Inflammasome, ETBR Signaling, and miRNAs in Stress-Induced Depression-Like Behavior: a Modulatory Role for SGLT2 Inhibitors

Depression is an overwhelming health concern, and many patients fail to optimally respond to available standard therapies. Neuroplasticity and blood-brain barrier (BBB) integrity are the cornerstones of a well-functioning central nervous system, but they are vulnerable to an overly active NLRP3 inflammasome pathway that can also indirectly trigger the release of ET-1 and contribute to the ET system disturbance, which further damages stress resilience mechanisms. Here, the promising yet unexplored antidepressant potential of dapagliflozin (Dapa), a sodium-glucose co-transporter-2 inhibitor, was investigated by assessing its role in the modulation of the NLRP3 inflammasome pathway and ETBR signal transduction, and their impact on neuroplasticity and BBB integrity in an animal model of depression. Dapa (1 mg/kg/day; p.o.) with and without BQ-788 (1 mg/kg/day; i.p.), a specific ETBR blocker, were administered to adolescent male Wistar rats exposed to a 5-week chronic unpredictable stress protocol. The depressive animals demonstrated marked activation of the NLRP3 inflammasome pathway (NF-κB/NLRP3/caspase-1/IL/TNF-α), which was associated with both peripheral and central inflammatory responses. The ET system was disrupted, with noticeable reduction in miR-125a-5p and ETBR gene expression. Cortical ZO-1 expression was downregulated under the influence of NLRP3/TNF-α/miR-501-3p signaling, along with a prominent reduction in hippocampal BDNF and synapsin-1. With ETBR up-regulation being a cornerstone outcome, Dapa administration efficiently created an overall state of resilience, improved histopathological and behavioral variables, and preserved BBB function. These observations were further verified by the results obtained with BQ-788 co-administration. Thus, Dapa may exert its antidepressant action by reinforcing BBB integrity and promoting neuroplasticity through manipulation of the NLRP3/ET-1/ETBR/BDNF/ZO-1 axis, with a significant role for ETBR signaling. Graphical illustration for the proposed mechanisms of the anti-depressant potential of Dapa. Dapa suppressed NLRP3 inflammasome activation and assembly with subsequent inhibition of pro-inflammatory ILs. This results in attenuation of neuro-inflammation, BBB disruption, glial cell activation, TNF-α and ET-1 release, and the enhanced production of neurotrophins. The role of ETBR signaling was emphasized; Dapa possibly augmented ETBR expression, which is thought to boost neurotrophins production. The ETBR blocker, BQ-788, suppressed most of the positive outcomes of Dapa. Finally, miR-125a-5p and miR-501-3p that played major roles in these pathological pathways were modulated by Dapa. It is not yet clear whether Dapa has a direct or rather indirect effect on their expression. BBB, blood-brain barrier; Dapa, dapagliflozin; ET-1, endothelin-1; ETBR, endothelin B receptor; IL, interleukin; NF-κB, nuclear factor kappa B; NLRP3, nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing protein 3; TNF-α, tumor necrosis factor-α. Created with BioRender.com.

Brain-Derived Neurotrophic Factor during Oral Glucose Tolerance Test Predicts Cardiovascular Outcomes

We investigated if brain-derived neurotrophic factor (BDNF) accumulation after glucose intake could predict cardiovascular outcomes. We enrolled patients admitted for angiography due to angina. After their conditions stabilized, serum BDNF levels were detected at 0, 30, and 120 min during oral glucose tolerance test (OGTT). Area under the curve (AUC) of BDNF was calculated. The first occurrence of nonfatal myocardial infarction, nonfatal stroke, and all-cause mortality served as the primary composite endpoint. Of 480 enrolled patients, 428 completed the follow-up, and 36 primary endpoint events occurred during a median follow-up of 4.4 years. The area under the receiver operating characteristic curve significantly increased from 0.61 (95% confidence interval (CI): 0.52–0.73) for the Framingham risk score (FRS) alone model to 0.72 (95%CI: 0.63–0.81) for the AUC of BDNF plus FRS model (p = 0.016) for predicting the primary endpoint, but not to 0.65 (95%CI: 0.55–0.75) for the fasting BDNF plus FRS model (p = 0.160). Grouped by median AUC of BDNF of 38.0 (ng/mL) × h, the low BDNF group had a significantly higher risk of the endpoint than the high BDNF group (hazard ratio = 3.410, 95%CI: 1.520–7.653, p = 0.003). In conclusion, AUC of BDNF during OGTT could be superior to fasting BDNF for predicting a low cardiovascular risk.

NLRP3 inflammasome activation in platelets in response to sepsis

Sepsis is a complex syndrome characterized by organ dysfunction and a dysregulated immune host response to infection. There is currently no effective treatment for sepsis, but platelets have been proposed as a potential therapeutic target for the treatment of sepsis. We hypothesized that the NLRP3 inflammasome is activated in platelets during sepsis and may be associated with multiorgan injury in response to polymicrobial sepsis. Polymicrobial sepsis was induced by cecal ligation and puncture (CLP) in 12‐ to 13‐week‐old male Sprague–Dawley rats. The necrotic cecum was removed at 24 h post‐CLP. At 72 h post‐CLP, activated platelets were significantly increased in CLP versus Sham rats. Colocalization of NLRP3 inflammasome components was observed in platelets from CLP rats at 72 h post‐CLP. Plasma, pulmonary, and renal levels of IL‐1β and IL‐18 were significantly higher in CLP rats compared to Sham controls. Soluble markers of endothelial permeability were increased in CLP versus Sham. Renal and pulmonary histopathology were markedly elevated in CLP rats compared to Sham controls. NLRP3 is activated in platelets in response to CLP and is associated with inflammation, endothelial permeability and multiorgan injury. Our results indicate that activated platelets may play a role to cause multiorgan injury in sepsis and may have therapeutic potential for the treatment of sepsis multiorgan injury.

Puerarin Protects Against LPS-Induced Vascular Endothelial Cell Hyperpermeability via Preventing Downregulation of Endothelial Cadherin

In the present study, we aimed to investigate the effects of puerarin on the hyperpermeability of vascular endothelial cells induced by lipopolysaccharide (LPS) and its underlying mechanisms. Human umbilical vein endothelial cells (HUVECs) were pre-incubated with puerarin (25, 50, and 100 μM) for 1 h, and then exposed to LPS (1 μg/mL). The monolayer permeability of endothelial cells was assessed by measuring the paracellular flux of FITC-dextran 40,000 (FD40). The expression of vascular endothelial cadherin (VE-cadherin) in HUVECs was examined by Western blotting analysis. A total of 18 mice were randomly assigned into three groups as follows: control group, LPS group, and puerarin group. The pulmonary W/D ratio (wet-to-dry weight ratios) was calculated, and the lung morphology was examined. The levels of TNF-α and IL-1β in cell supernatant and mouse serum were determined by ELISA. Compared with the control group, LPS obviously increased the flux of FD40 and the monolayer permeability, raised the levels of TNF-α and IL-1β in cell supernatant, and reduced the VE-cadherin expression in HUVECs. However, puerarin (25, 50, and 100 μM) was able to relieve such LPS-induced increase in flux of FD40 and then reduce the hyperpermeability. Puerarin decreased the levels of TNF-α and IL-1β in cell supernatant and increased the VE-cadherin expression in HUVECs (P < 0.05). Moreover, LPS obviously increased the levels of TNF-α and IL-1β in mouse serum and elevated the pulmonary W/D ratios, resulting in lung injury. However, all of above-mentioned LPS-induced changes were improved by puerarin pre-treatment. Puerarin could alleviate LPS-induced hyperpermeability in endothelial cells via preventing downregulation of endothelial cadherin.

Oligodendrocytes upregulate blood-brain barrier function through mechanisms other than the PDGF-BB/PDGFRα pathway in the barrier-tightening effect of oligodendrocyte progenitor cells

White matter lesions are associated with impairment of the blood-brain barrier (BBB), an essential component of the cerebrovasculature. The BBB allows the brain to maintain its highly specialized microenvironment by restricting entry of blood-borne substances including molecules that induce myelin damage. Accumulating evidence suggests that interactions between brain endothelial cells and neighboring cells, including oligodendrocyte progenitor cells (OPCs), are required for the induction and maintenance of BBB function. Here, we compared the ability of OPCs and oligodendrocytes to modulate BBB integrity using co-cultures of rat brain endothelial cells with OPCs or oligodendrocytes. We found that OPCs lowered the brain endothelial permeability to sodium fluorescein, and this enhancement of BBB function was prevented by treatment with AG1296 (a PDGFRα inhibitor). Oligodendrocytes also enhanced BBB integrity. Pharmacological inhibition of PDGFRα did not affect the oligodendrocyte-induced BBB facilitation. These data indicate that oligodendrocytes enhance BBB integrity through pathways other than PDGF-BB/PDGFRα signaling triggered by the brain endothelial cell-derived PDGF-BB. Therefore, our findings suggest that oligodendrocytes constitutively support BBB integrity through soluble factors. Crosstalk between brain endothelial cells and oligodendrocytes could play a facilitatory role in maintaining BBB integrity in the white matter.

Brain-derived neurotrophic factor preserves intestinal mucosal barrier function and alters gut microbiota in mice

The intestinal mucosal barrier (IMB) enables the intestine to provide adequate containment of luminal microorganisms and molecules while preserving the ability to absorb nutrients. In this study, we explored the effect of brain-derived neurotrophic factor (BDNF) on IMB function and gut microbiota in mice. BDNF gene knock-out mice (the BDNF^+/- group) and wild-type mice (the BDNF^+/+ group) were selected. The gut microbiota of these mice was analyzed by denaturing gradient gel electrophoresis (DGGE) assay. The ultrastructure of the ileum and the colonic epithelium obtained from decapitated mice were observed by transmission electron microscopy. The protein expression of epithelial tight junction proteins, zonula occludens-1 (ZO-1) and occludin was detected by immunohistochemistry staining. The protein expression of claudin-1 and claudin-2 was determined by Western blotting. The DGGE band patterns of gut microbiota in the BDNF^+/- group were significantly different from that in the BDNF^+/+ group, which indicated that the BDNF expression alters the gut microbiota in mice. Compared with the BDNF^+/+ group, the BDNF^+/- group presented no significant difference in the ultrastructure of ileal epithelium; however, a significant difference was observed in the colonic epithelial barrier, manifested by decreased microvilli, widening intercellular space and bacterial invasion. Compared with the BDNF^+/+ group, the expression of ZO-1 and occludin in the BDNF^+/- group was significantly decreased. The expression of claudin-1 in the BDNF^+/- group was significantly reduced, while the expression of claudin-2 was elevated. These findings indicate that BDNF preserves IMB function and modulates gut microbiota in mice.

Rat Cranial Bone-Derived Mesenchymal Stem Cell Transplantation Promotes Functional Recovery in Ischemic Stroke Model Rats

The functional disorders caused by central nervous system (CNS) diseases, such as ischemic stroke, are clinically incurable and current treatments have limited effects. Previous studies suggested that cell-based therapy using mesenchymal stem cells (MSCs) exerts therapeutic effects for ischemic stroke. In addition, the characteristics of MSCs may depend on their sources. Among the derived tissues of MSCs, we have focused on cranial bones originating from the neural crest. We previously demonstrated that the neurogenic potential of human cranial bone-derived MSCs (cMSCs) was higher than that of human iliac bone-derived MSCs. Therefore, we presumed that cMSCs have a higher therapeutic potential for CNS diseases. However, the therapeutic effects of cMSCs have not yet been elucidated in detail. In the present study, we aimed to demonstrate the therapeutic effects of transplantation with rat cranial bone-derived MSCs (rcMSCs) in ischemic stroke model rats. The mRNA expression of brain-derived neurotrophic factor and nerve growth factor was significantly stronger in rcMSCs than in rat bone marrow-derived MSCs (rbMSCs). Ischemic stroke model rats in the rcMSC transplantation group showed better functional recovery than those in the no transplantation and rbMSC transplantation groups. Furthermore, in the in vitro study, the conditioned medium of rcMSCs significantly suppressed the death of neuroblastoma × glioma hybrid cells (NG108-15) exposed to oxidative and inflammatory stresses. These results suggest that cMSCs have potential as a candidate cell-based therapy for CNS diseases.

Brain-Derived Neurotrophic Factor Modulates Intestinal Barrier by Inhibiting Intestinal Epithelial Cells Apoptosis in Mice

We aimed to investigate the effects of brain-derived neurotrophic factor (BDNF) on apoptosis of intestinal epithelial cells (IECs) and alterations of intestinal barrier integrity using BDNF knock-out mice model. Colonic tissues from BDNF+/+ mice and BDNF+/- mice were prepared for this study. The integrity of colonic mucosa was evaluated by measuring trans-mucosa electrical resistance and tissue conductance in Ussing chamber. The colonic epithelial structure was analyzed by transmission electron microscopy. Apoptosis involvement was determined with TUNEL staining, active caspase-3 immunostaining and Western blotting for the protein expression of active caspase-3, Bax and Bcl-2. The expression levels and distribution of tight junction proteins were evaluated by immunohistochemistry or Western blots. Compared with BDNF+/+ mice, BDNF+/- mice displayed impaired integrity and ultrastructure alterations in their colonic mucosa, which was characterized by diminished microvilli, mitochondrial swelling and epithelial cells apoptosis. Altered intestinal barrier function was linked to excessive apoptosis of IECs demonstrated by the higher proportion of TUNEL-positive apoptotic cells and enhanced caspase activities in BDNF+/- mice. Increased expression of Bax and claudin-2 proteins and reduced Bcl-2 and tight junction proteins (occludin, ZO-1 and claudin-1) expression were also detected in the colonic mucosa of BDNF+/- mice. BDNF may play a role in the maintenance of intestinal barrier integrity via its anti-apoptotic properties.

Mechanisms of macular edema: Beyond the surface

Macular edema consists of intra- or subretinal fluid accumulation in the macular region. It occurs during the course of numerous retinal disorders and can cause severe impairment of central vision. Major causes of macular edema include diabetes, branch and central retinal vein occlusion, choroidal neovascularization, posterior uveitis, postoperative inflammation and central serous chorioretinopathy. The healthy retina is maintained in a relatively dehydrated, transparent state compatible with optimal light transmission by multiple active and passive systems. Fluid accumulation results from an imbalance between processes governing fluid entry and exit, and is driven by Starling equation when inner or outer blood-retinal barriers are disrupted. The multiple and intricate mechanisms involved in retinal hydro-ionic homeostasis, their molecular and cellular basis, and how their deregulation lead to retinal edema, are addressed in this review. Analyzing the distribution of junction proteins and water channels in the human macula, several hypotheses are raised to explain why edema forms specifically in the macular region. "Pure" clinical phenotypes of macular edema, that result presumably from a single causative mechanism, are detailed. Finally, diabetic macular edema is investigated, as a complex multifactorial pathogenic example. This comprehensive review on the current understanding of macular edema and its mechanisms opens perspectives to identify new preventive and therapeutic strategies for this sight-threatening condition.

BDNF modulates intestinal barrier integrity through regulating the expression of tight junction proteins

BACKGROUND

Brain-derived neurotrophic factor (BDNF) may play a vital role in the homeostatic regulation of intestinal barrier integrity. We aimed to investigate the physiological role of BDNF in maintaining the intestinal epithelial barrier using postinflammatory irritable bowel syndrome (PI-IBS) mice and explore the underlying molecular mechanisms using intestinal epithelial cells in vitro.

METHODS

Postinflammatory-IBS mice were induced by intrarectal administration of trinitrobenzene sulfonic acid and allowed to recover for 28 days. Frequency of defecation, fecal water content, colonic epithelial integrity and expressions of BDNF and tight junction (TJ) proteins (occludin, ZO-1, claudin-1, claudin-2) of the PI-IBS mice were investigated. Based on the results of animal studies, we further performed RT-PCR and Western blots to assess how BDNF stimulation and BDNF knockdown impacted TJ proteins in the ht-29 intestinal epithelial cells.

KEY RESULTS

Water content of stools was significantly increased in the PI-IBS mice compared with controls. Colonic mucosa from the PI-IBS mice displayed epithelial barrier defects and exhibited increased protein expressions of BDNF and claudin-2 and decreased protein expressions of occludin, ZO-1 and claudin-1. Furthermore, a siRNA against BDNF in the ht-29 cells could effectively suppress BDNF gene and protein expressions, and subsequently reduce TJ gene and protein levels. When the ht-29 cells were incubated with different doses of exogenous BDNF, significant increases of occludin, ZO-1 and claudin-1 and decreases of claudin-2 protein were observed.

CONCLUSIONS & INFERENCES

BDNF may play a role in regulating intestinal epithelial barrier via affecting the expression of TJ proteins.

Serum brain-derived neurotrophic factor and risk of atrial fibrillation

Brain-derived neurotrophic factor (BDNF) is expressed by endothelial cells and can affect cardiovascular function. We examined if serum BDNF was associated with risk of incident atrial fibrillation (AF) in the Framingham Heart Study.

METHODS

We studied individuals without an AF diagnosis at baseline from the Framingham original and offspring cohorts. We used age- and sex-adjusted, and multivariable-adjusted Cox proportional hazards regression models to examine the association of serum BDNF concentrations with 10-year risk of incident AF.

RESULTS

We studied 3,457 participants (mean age 65±11years, 58% women). During follow-up, 395 participants developed AF. In unadjusted analysis, higher mean serum BDNF concentration was associated with lower incidence of AF (hazard ratio 0.89 per SD, 95% CI 0.80-0.99). In multivariable-adjusted analyses, serum BDNF concentration was not significantly associated with incident AF (hazard ratio 0.98 per SD, 95% CI 0.88-1.09). Compared with the lowest quartile, BDNF levels in the other quartiles were not associated with risk of AF in multivariable-adjusted analyses. No interactions between sex or age with serum BDNF concentrations and risk of AF were found.

CONCLUSIONS

In our prospective, community-based sample, we did not find a statistically significant association of serum BDNF levels with risk of incident AF.