Indole Propionic Acid Increases T Regulatory Cells and Decreases T Helper 17 Cells and Blood Pressure in Mice with Salt-Sensitive Hypertension

Hypertension affects over a billion adults worldwide and is a major risk factor for cardiovascular disease. Studies have reported that the microbiota and its metabolites regulate hypertension pathophysiology. Recently, tryptophan metabolites have been identified to contribute to and inhibit the progression of metabolic disorders and cardiovascular diseases, including hypertension. Indole propionic acid (IPA) is a tryptophan metabolite with reported protective effects in neurodegenerative and cardiovascular diseases; however, its involvement in renal immunomodulation and sodium handling in hypertension is unknown. In the current study, targeted metabolomic analysis revealed decreased serum and fecal IPA levels in mice with L-arginine methyl ester hydrochloride (L-NAME)/high salt diet-induced hypertension (LSHTN) compared to normotensive control mice. Additionally, kidneys from LSHTN mice had increased T helper 17 (Th17) cells and decreased T regulatory (Treg) cells. Dietary IPA supplementation in LSHTN mice for 3 weeks resulted in decreased systolic blood pressure, along with increased total 24 h and fractional sodium excretion. Kidney immunophenotyping demonstrated decreased Th17 cells and a trend toward increased Treg cells in IPA-supplemented LSHTN mice. In vitro, naïve T cells from control mice were skewed into Th17 or Treg cells. The presence of IPA decreased Th17 cells and increased Treg cells after 3 days. These results identify a direct role for IPA in attenuating renal Th17 cells and increasing Treg cells, leading to improved sodium handling and decreased blood pressure. IPA may be a potential metabolite-based therapeutic option for hypertension.

A Kidney-Targeted Nanoparticle to Augment Renal Lymphatic Density Decreases Blood Pressure in Hypertensive Mice

Chronic interstitial inflammation and renal infiltration of activated immune cells play an integral role in hypertension. Lymphatics regulate inflammation through clearance of immune cells and excess interstitial fluid. Previously, we demonstrated increasing renal lymphangiogenesis prevents hypertension in mice. We hypothesized that targeted nanoparticle delivery of vascular endothelial growth factor-C (VEGF-C) to the kidney would induce renal lymphangiogenesis, lowering blood pressure in hypertensive mice. A kidney-targeting nanoparticle was loaded with a VEGF receptor-3-specific form of VEGF-C and injected into mice with angiotensin II-induced hypertension or LNAME-induced hypertension every 3 days. Nanoparticle-treated mice exhibited increased renal lymphatic vessel density and width compared to hypertensive mice injected with VEGF-C alone. Nanoparticle-treated mice exhibited decreased systolic blood pressure, decreased pro-inflammatory renal immune cells, and increased urinary fractional excretion of sodium. Our findings demonstrate that pharmacologically expanding renal lymphatics decreases blood pressure and is associated with favorable alterations in renal immune cells and increased sodium excretion.

Expanded renal lymphatics improve recovery following kidney injury

Acute kidney injury (AKI) is a major cause of patient mortality and a major risk multiplier for the progression to chronic kidney disease (CKD). The mechanism of the AKI to CKD transition is complex but is likely mediated by the extent and length of the inflammatory response following the initial injury. Lymphatic vessels help to maintain tissue homeostasis through fluid, macromolecule, and immune modulation. Increased lymphatic growth, or lymphangiogenesis, often occurs during inflammation and plays a role in acute and chronic disease processes. What roles renal lymphatics and lymphangiogenesis play in AKI recovery and CKD progression remains largely unknown. To determine if the increased lymphatic density is protective in the response to kidney injury, we utilized a transgenic mouse model with inducible, kidney-specific overexpression of the lymphangiogenic protein vascular endothelial growth factor-D to expand renal lymphatics. "KidVD" mouse kidneys were injured using inducible podocyte apoptosis and proteinuria (POD-ATTAC) or bilateral ischemia reperfusion. In the acute injury phase of both models, KidVD mice demonstrated a similar loss of function measured by serum creatinine and glomerular filtration rate compared to their littermates. While the initial inflammatory response was similar, KidVD mice demonstrated a shift toward more CD4+ and fewer CD8+ T cells in the kidney. Reduced collagen deposition and improved functional recovery over time was also identified in KidVD mice. In KidVD-POD-ATTAC mice, an increased number of podocytes were counted at 28 days post-injury. These data demonstrate that increased lymphatic density prior to injury alters the injury recovery response and affords protection from CKD progression.

Common Metabolites in Two Different Hypertensive Mouse Models: A Serum and Urine Metabolome Study

Recent metabolomics studies have identified a wide array of microbial metabolites and metabolite pathways that are significantly altered in hypertension. However, whether these metabolites play an active role in pathogenesis of hypertension or are altered because of this has yet to be determined. In the current study, we hypothesized that metabolite changes common between hypertension models may unify hypertension's pathophysiology with respect to metabolites. We utilized two common mouse models of experimental hypertension: L-arginine methyl ester hydrochloride (L-NAME)/high-salt-diet-induced hypertension (LSHTN) and angiotensin II induced hypertension (AHTN). To identify common metabolites that were altered across both models, we performed untargeted global metabolomics analysis in serum and urine and the resulting data were analyzed using MetaboAnalyst software and compared to control mice. A total of 41 serum metabolites were identified as being significantly altered in any hypertensive model compared to the controls. Of these compounds, 14 were commonly changed in both hypertensive groups, with 4 significantly increased and 10 significantly decreased. In the urine, six metabolites were significantly altered in any hypertensive group with respect to the control; however, none of them were common between the hypertensive groups. These findings demonstrate that a modest, but potentially important, number of serum metabolites are commonly altered between experimental hypertension models. Further studies of the newly identified metabolites from this untargeted metabolomics analysis may lead to a greater understanding of the association between gut dysbiosis and hypertension.

Abstract MP40: Microbiome-associated Metabolites Are Altered In Mouse Models Of Hypertension

Recent studies suggest that the microbiome plays a key role in hypertension and associated inflammation. Microbiota produce metabolites that may lead to activated pro-inflammatory immune cells and contribute to hypertension; however, the altered metabolites in multiple models of hypertension is currently unknown. We hypothesized that there are significant differences in metabolomic profiles between normotensive and hypertensive mice. We utilized two mouse models of hypertension: L-arginine methyl ester hydrochloride (L-NAME)/high salt diet induced hypertension (LSHTN) and angiotensin II induced hypertension (A2HTN). Serum and fecal samples were collected at the end of the treatment period. Ultra-high performance liquid chromatography and tandem mass spectrometry were performed to identify the biochemical composition of each sample. Random Forest Analysis was performed to classify each sample based on similarities and differences in metabolite composition. These procedures were performed by Metabolon, Inc. A total of 1,066 and 1,028 biochemicals were measured in serum and feces, respectively. There were 263 biochemicals in LSHTN serum and 122 biochemicals in A2HTN serum that were statistically different from controls (p≤0.05). There were 298 biochemicals in LSHTN feces and 64 biochemicals in A2HTN feces that were statistically different from controls (p≤0.05). Five biochemical metabolite groups were shown to have significant differences between hypertensive groups and controls: aromatic amino acids, bile acids and sterols, benzoates, fatty acids, and diacylglycerols. Tryptophan metabolites were significantly reduced in the serum of LSHTN mice but not in the serum of A2HTN mice. Serum tyrosine and benzoate metabolites showed varied differences between the two hypertensive groups. Serum fatty acid beta oxidation metabolites were significantly reduced in both hypertensive models but were significantly increased in the feces of mice with LSHTN. In conclusion, this study provided significant analysis of metabolite changes in two hypertension mouse models. Further investigation of the roles these metabolites play in hypertension may lead to targeted therapeutic interventions.

Abstract MP42: Metabolomic Study To Identify Common Metabolites In Two Different Mouse Models Of Hypertension

Metabolomic Study to Identify Common Metabolites in Two Different Mouse Models of Hypertension

Recent studies have reflected the importance of the body’s microbiome and associated metabolites and their changes in hypertension. In the current study, we hypothesized that metabolite changes common between hypertension models may unify hypertension’s pathophysiology with respect to metabolites. Two different mice models of experimental hypertension were used in the study: (1) L-arginine methyl ester hydrochloride (L-NAME)/High salt diet induced hypertension (LSHTN) and (2) angiotensin II induced hypertension (AHTN). Untargeted global metabolomics analysis in serum and urine samples were performed to identify common metabolites altered across both hypertensive models, and the resulting data were analyzed using MetaboAnalyst software and compared to control mice. A list of metabolites that were altered significantly in both models of hypertension were identified. A total of 41 serum metabolites were identified as being altered significantly in any hypertensive model compared to controls. Of these, however, only 4 were increased significantly, and 10 were decreased significantly in common across both hypertensive groups. In the urine, 6 metabolites were altered significantly in any hypertensive group with respect to control, however, 0 of them were common between the hypertensive groups. These findings demonstrate that a modest, but potentially important, number of serum metabolites are commonly altered between experimental hypertension models. Further studies to understand the role of these identified metabolites may lead to a greater understanding of the association between gut dysbiosis and hypertension. Submitted to American Heart Association Council on Hypertension Scientific Sessions (September 27-29, 2021, Virtual)Abstract#: 21-HBPR-A-578-AHA

Dichotomous effects on lymphatic transport with loss of caveolae in mice

AIM

Fluid and macromolecule transport from the interstitium into and through lymphatic vessels is necessary for tissue homeostasis. While lymphatic capillary structure suggests that passive, paracellular transport would be the predominant route of macromolecule entry, active caveolae-mediated transcellular transport has been identified in lymphatic endothelial cells (LECs) in vitro. Caveolae also mediate a wide array of endothelial cell processes, including nitric oxide regulation. Thus, how does the lack of caveolae impact "lymphatic function"?

METHODS

Various aspects of lymphatic transport were measured in mice constitutively lacking caveolin-1 ("CavKO"), the protein required for caveolae formation in endothelial cells, and in mice with a LEC-specific Cav1 gene deletion (Lyve1-Cre x Cav1^flox/flox ; "LyCav") and ex vivo in their vessels and cells.

RESULTS

In each model, lymphatic architecture was largely unchanged. The lymphatic conductance, or initial tissue uptake, was significantly higher in both CavKO mice and LyCav mice by quantitative microlymphangiography and the permeability to 70 kDa dextran was significantly increased in monolayers of LECs isolated from CavKO mice. Conversely, transport within the lymphatic system to the sentinel node was significantly reduced in anaesthetized CavKO and LyCav mice. Isolated, cannulated collecting vessel studies identified significantly reduced phasic contractility when lymphatic endothelium lacks caveolae. Inhibition of nitric oxide synthase was able to partially restore ex vivo vessel contractility.

CONCLUSION

Macromolecule transport across lymphatics is increased with loss of caveolae, yet phasic contractility reduced, resulting in reduced overall lymphatic transport function. These studies identify lymphatic caveolar biology as a key regulator of active lymphatic transport functions.

Abstract 143: Enhancing Renal Lymphatic Vessel Density Blunts Both Salt-Sensitive and Angiotensin II-Dependent Hypertension in Mice

Sodium retention is a hallmark of most forms of experimental hypertension. Renal lymphatics maintain fluid homeostasis by draining cortical interstitial fluid to the draining lymph node. Our lab has previously demonstrated that augmenting renal lymphatics prevents hypertension, but whether this can treat hypertension and whether expanding renal lymphatics alters renal sodium handling remain unknown. Our hypotheses were that augmenting renal lymphatic vessel density after hypertension is established will treat salt sensitive hypertension (SSHTN) and angiotensin II-induced hypertension (AIIHTN) and that this will be accompanied by an increase in urinary sodium excretion. To test our hypotheses, we utilized transgenic mice that overexpress the lymphangiogenic growth factor VEGF-D specifically in the kidney when administered doxycycline (KidVD+ mice). KidVD+ mice and KidVD- littermates were made salt-sensitive by treatment with L-NAME (0.5 mg/mL) for two weeks, followed by a washout period of two weeks, and then given a 4% high salt diet for four weeks. To induce AIIHTN, mice were infused with angiotensin II (490 ng/kg/min) for four weeks. Doxycycline was administered to all mice a week after beginning the high salt diet or a week after angiotensin II infusion. Prior to doxycycline initiation, KidVD- and KidVD+ mice were hypertensive (SSHTN SBP: 130±2 and 134±2 mmHg, respectively; AIIHTN SBP: 125±2 and 128±2 mmHg, respectively). Compared to KidVD- mice, doxycycline administration for three weeks augmented renal lymphatics in KidVD+ mice and significantly decreased blood pressure after four weeks of high salt diet or angiotensin II (SSHTN SBP: 134±4 vs. 125±2 mmHg; p<0.05; AIIHTN: 145±3 vs. 125±5 mmHg; p<0.05). The reduction in blood pressure was accompanied by an increase in urinary fractional excretion of sodium in SSHTN and AIIHTN KidVD+ mice. AIIHTN induced an elevated glomerular filtration rate (GFR) in KidVD- mice while this was reduced in KidVD+ mice; however, GFR was unaltered in SSHTN KidVD+ mice. Thus, augmenting renal lymphatics increased fractional excretion of sodium and lowered blood pressure in both mouse models of hypertension. Augmenting renal lymphatics may be a promising anti-hypertensive and natriuretic therapeutic strategy.

Abstract P3020: Therapeutic Induction of Renal Lymphatic Expansion Attenuates Blood Pressure in Mice With L-NAME Hypertension

Renal immune cell infiltration and accompanying inflammation activates renal sodium transporters leading to sodium retention and hypertension. Lymphatic vessels traffic interstitial immune cells to the draining lymph nodes and help resolve inflammation. We have previously demonstrated that genetically inducing renal lymphangiogenesis prevents hypertension associated with a reduction in renal immune cell accumulation; however, it is unknown whether augmenting renal lymphatics can treat hypertension. Our hypothesis was that augmenting renal lymphatics after hypertension is established will lower blood pressure during L-NAME-induced hypertension (LHTN). Transgenic mice that overexpress the lymphangiogenic signal VEGF-D only in the kidney upon doxycycline administration (KidVD+ mice) and KidVD- littermates were administered L-NAME (0.5 mg/mL) in their drinking water for four weeks with doxycycline initiated at the second week of L-NAME. Treatment with L-NAME for one week induced LHTN in both KidVD- and KidVD+ mice (SBP: 134±4 and 142±5 mmHg, respectively). However, doxycycline-induced renal lymphangiogenesis significantly decreased blood pressure in KidVD+ mice compared to KidVD- mice after four weeks of L-NAME (SBP: 127±5 vs. 151±6 mmHg; p<0.05). This was associated with a significant decrease in renal CD11c + F4/80 - monocytes and a significant increase in 24-hour urinary sodium excretion and fractional excretion of sodium in KidVD+ mice. Urinary volume over 24 hours was also increased in KidVD+ mice (1.7±0.8 vs. 3±0.9 mL/24 hours; p<0.05); however, this was not associated with a change in glomerular filtration rate. Thus, augmenting renal lymphatics lowers blood pressure in mice with LHTN and this is associated with a decrease in renal monocyte accumulation and an increase in urinary sodium excretion. Augmenting renal lymphatics may be a promising anti-hypertensive and natriuretic therapeutic strategy.

Impregnation of catheters with anacardic acid from cashew nut shell prevents Staphylococcus aureus biofilm development

AIM

The effect of anacardic acid impregnation on catheter surfaces for the prevention of Staphylococcus aureus attachments and biofilm formations were evaluated.

METHODS AND RESULTS

Silicon catheter tubes were impregnated using different concentrations of anacardic acids (0·002-0·25%). Anacardic acids are antibacterial phenolic lipids from cashew nut (Anacardium occidentale) shell oil. Anacardic acid-impregnated silicon catheters revealed no significant haemolytic activity and were cytocompatible against fibroblast cell line (L929). Sustained release of anacardic acids was observed for 4 days. Anacardic acid-impregnated silicon catheters efficiently inhibited S. aureus colonization and the biofilm formation on its surface. The in vivo antibiofilm activity of anacardic acid-impregnated catheters was tested in an intraperitoneal catheter-associated medaka fish infection model. Significant reduction in S. aureus colonization on anacardic acid-impregnated catheter tubes was observed.

CONCLUSIONS

Our data suggest that anacardic acid-impregnated silicon catheters may help in preventing catheter-related staphylococcal infections.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study opens new directions for designing antimicrobial phytochemical-coated surfaces with ideal antibiofilm properties and could be of great interest for biomedical research scientists.

Anti-staphylococcal Activity of Injectable Nano Tigecycline/Chitosan-PRP Composite Hydrogel Using Drosophila melanogaster Model for Infectious Wounds

Compared to the current treatment modalities, the use of an injectable hydrogel system, loaded with antibiotic encapsulated nanoparticles for the purpose of treating Staphylococcus aureus (S. aureus) chronic wound infections have several advantages. These include adhesiveness to infection site, reduced frequency of dressings, sustained drug release, inhibition of bacterial growth, and increased healing. In the present work tigecycline nanoparticles were loaded into chitosan-platelet-rich plasma (PRP) hydrogel. The tigecycline nanoparticles (95 ± 13 nm) were synthesized through ionic cross-linking method using chitosan, tripolyphosphate, and tigecycline and characterized by dynamic light scattering (DLS), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FT-IR). The synthesized nanoparticles and activated PRP powder were mixed with chitosan hydrogel to form a homogeneous gel. Rheology studies have confirmed the shear thinning property, thermal stability, and injectability of the prepared gel systems. The gel system was further assessed for its drug release property and found that it was released in a sustained manner. Hemolysis and blood-clotting assays demonstrated that the gel system was neither a hemolysin nor a hamper to the clotting cascade. Cell viability results showed that these nanoparticles were cyto-compatible. The bioactivity of PRP loaded chitosan gel toward fibroblast cell line was studied using cell proliferation and migration assay. In vitro antibacterial studies revealed that the gel system inhibited bacterial growth to a great extent. The antibacterial activity was further analyzed using ex vivo porcine skin assay. In vivo anti-Staphylococcal activity of the prepared hydrogels was studied using a Drosophila melanogaster infection model. The tigecycline and tigecycline nanoparticle incorporated chitosan gel showed a significant antibacterial activity against S. aureus. Thus, the gel system is an effective medium for antibiotic delivery and can be applied on the infection sites to effectively forestall various skin infections caused by S. aureus.

Composite hydrogel of chitosan-poly(hydroxybutyrate-co-valerate) with chondroitin sulfate nanoparticles for nucleus pulposus tissue engineering

Intervertebral disc degeneration, occurring mainly in nucleus pulposus (NP), is a leading cause of low back pain. In seeking to mitigate this condition, investigators in the field of NP tissue engineering have increasingly studied the use of hydrogels. However, these hydrogels should possess appropriate mechanical strength and swelling pressure, and concurrently support the proliferation of chondrocyte-like cells. The objective of this study was to develop and validate a composite hydrogel for NP tissue engineering, made of chitosan-poly(hydroxybutyrate-co-valerate) (CP) with chondroitin sulfate (CS) nanoparticles, without using a cross linker. The water uptake ability, as well as the viscoelastic properties of this composite hydrogel, was similar to native tissue, as reflected in the complex shear modulus and stress relaxation values. The hydrogel could withstand varying stress corresponding to daily activities like lying down (0.01 MPa), sitting (0.5 MPa) and standing (1.0 MPa) under dynamic conditions. The hydrogels were stable in PBS for 2 weeks and its stiffness, elastic and viscous modulus did not alter significantly during this period. Both CP and CP-CS hydrogels could assist the viability and adhesion of adipose derived rat mesenchymal stem cells (ADMSCs). The viability and chondrogenic differentiation of MSCs was significantly enhanced in presence of CS nanoparticles. Thus, CS nanoparticles-incorporated chitosan-PHBV hydrogels offer great potential for NP tissue engineering.

ZnO nanoparticle incorporated nanostructured metallic titanium for increased mesenchymal stem cell response and antibacterial activity

Recent trends in titanium implants are towards the development of nanoscale topographies that mimic the nanoscale properties of bone tissue. Although the nanosurface promotes the integration of osteoblast cells, infection related problems can also occur, leading to implant failure. Therefore it is imperative to reduce bacterial adhesion on an implant surface, either with or without the use of drugs/antibacterial agents. Herein, we have investigated two different aspects of Ti surfaces in inhibiting bacterial adhesion and concurrently promoting mammalian cell adhesion. These include (i) the type of nanoscale topography (Titania nanotube (TNT) and Titania nanoleaf (TNL)) and (ii) the presence of an antibacterial agent like zinc oxide nanoparticles (ZnOnp) on Ti nanosurfaces. To address this, periodically arranged TNT (80-120 nm) and non-periodically arranged TNL surfaces were generated by the anodization and hydrothermal techniques respectively, and incorporated with ZnOnp of different concentrations (375 μM, 750 μM, 1.125 mM and 1.5 mM). Interestingly, TNL surfaces decreased the adherence of staphylococcus aureus while increasing the adhesion and viability of human osteosarcoma MG63 cell line and human mesenchymal stem cells, even in the absence of ZnOnp. In contrast, TNT surfaces exhibited an increased bacterial and mammalian cell adhesion. The influence of ZnOnp on these surfaces in altering the bacterial and cell adhesion was found to be concentration dependent, with an optimal range of 375-750 μM. Above 750 μM, although bacterial adhesion was reduced, cellular viability was considerably affected. Thus our study helps us to infer that nanoscale topography by itself or its combination with an optimal concentration of antibacterial ZnOnp would provide a differential cell behavior and thereby a desirable biological response, facilitating the long term success of an implant.