Expedited Surgical Care of Appendicitis is Associated With Improved Resource Utilization

INTRODUCTION

Appendectomy for acute appendicitis is the most common pediatric intra-abdominal operation. Current literature supports the notion that modest in-hospital, preoperative delays are not associated with greater patient morbidity. However, there is less certainty regarding the role that hour-of-presentation plays in determining the timing of surgery. Thus, we aimed to evaluate how after-hours presentation may relate to the timing of surgery and to assess the outcomes and resource utilization associated with expedited appendectomy compared to nonexpedited.

METHODS

Patient records for children who underwent an appendectomy at a freestanding pediatric hospital from 2015 to 2019 were reviewed. Business hour presentations were defined as arrival at the emergency department from 7 AM to 6 PM. Primary outcomes were hospital length of stay (LOS), cost derived from the Pediatric Health Information System database, perforation, surgical complications, and 30-day readmissions.

RESULTS

Nine hundred forty-two patients underwent appendectomy over the study period. The median time to OR was 2.0 h in the expedited cohort and 9.8 h in the nonexpedited group. Presentation during business hours was associated with 4.4 higher odds (P < 0.001) of expedited workflow. Expedited appendectomies were associated with shorter hospital LOS (11.5 h, P < 0.001), less costly admissions ($1,155, P < 0.001); LOS measured in midnights, perforation and readmission rates were similar between groups.

CONCLUSIONS

We found reduced resource utilization associated with expedited appendectomy. Additionally, the demonstrated association between the time of presentation to the emergency department (ED) and the timing of surgery may be utilized to inform staffing and resource deployment decisions. Further research regarding the generalizability and sustainability of an expedited presurgical workflow in pediatric appendectomy is certainly indicated.

The costs and benefits of emergent surgical workflow for acute appendicitis in children

BACKGROUND

Controversy exists regarding how operative timing affects patient safety and resource utilization for acute appendicitis. Over 3 years, our institution trialed efforts to optimize appendectomy workflow. Our aim is to describe the ramifications of expediting appendectomy and implementing standardized protocols relative to historic controls.

METHODS

Patient records at a freestanding children's hospital were reviewed from synchronized 6-month periods from 2019 to 2021. During Year 1 (historic), no standardized workflows existed. In Year 2 (expedited), appendicitis management was protocoled using a clinical quality improvement bundle, which included performing appendectomies within two hours of diagnosis. In Year 3 (QI), operative timing was relaxed to the same calendar day while all prior QI initiatives continued. Descriptive statistics were performed, using hospital length of stay (LOS) as the primary outcome.

RESULTS

298 patients underwent appendectomy for acute appendicitis. The median expedited workflow LOS was 15.3 hours shorter (p = 0.003) than historic controls; however, this was sustained despite relaxation of surgical urgency in the QI workflow. No differences in perforation rates were observed. During the expedited workflow, OR overtime staffing expense increased by $90,000 with no significant change in hospital costs. In multivariate regression, perforation was the only variable associated with LOS.

CONCLUSION

Hospital LOS can be shortened by expediting appendectomy. However, in our institution this did not decrease hospital costs and was furthermore balanced by higher personnel expenses. A sustained decrease in LOS after relaxing operative urgency standards implies that concurrent QI initiatives represent a more effective and cost-efficient strategy to decrease hospital resource utilization.

LEVEL OF EVIDENCE

Level III.

Impact of the Affordable Care Act's Medicaid expansion on tertiary pediatric surgical care

BACKGROUND

Many children gained insurance with the 2014 Affordable Care Act's (ACA) Medicaid Expansion (ME), yet its impact on access to pediatric tertiary surgical care remains unknown. We examined the effect of ME on rates of elective, ambulatory surgery (EAS), especially among publicly-insured and ethnoracial-minority patients.

METHODS

Surgical patients ≤18 years between 2012 and 2018 were identified using the Pediatric Health Information System. Interrupted time series analyses were conducted to predict the monthly proportion of publicly-insured patients and EAS rates in ME and nonexpansion states.

RESULTS

3,270,842 patients were included. Nonexpansion states demonstrated a 1.10% (p<0.05) increase in the proportion of publicly-insured patients at ACA implementation, which then plateaued. No immediate change was observed in ME states, but there was an annual 1.08% (p<0.01) decrease in subsequent years. Publicly-insured EAS rates decreased by 1.09% (p<0.01) in nonexpansion states; no change was observed in ME states. A 3.36% (p<0.01) increase in EAS rates was observed in nonexpansion and ME states. The gap in EAS rates increased between private and publicly-insured patients in nonexpansion, but not ME states.

CONCLUSIONS

Increased coverage for children in ME states was not associated with more access to tertiary pediatric surgical care; however, while nonexpansion states saw an increase in insurance-based disparities, ME states did not. Though insurance coverage is critical to access, other factors may be contributing to persistent disparities in access to pediatric surgical care.

Trends in gastrostomy tube placement with concomitant Nissen fundoplication for infants and young children at Pediatric Tertiary Centers

PURPOSE

In infants and toddlers, gastrostomy tube placement (GT) is typically accompanied by consideration of concomitant Nissen fundoplication (NF). Historically, rates of NF have varied across providers and institutions. This study examines practice variation and longitudinal trends in NF at pediatric tertiary centers.

METHODS

Patients ≤ 2 years who underwent GT between 2008 and 2018 were identified in the Pediatric Health Information System database. Patient demographics and rates of NF were examined. Descriptive statistics were used to evaluate the variation in the proportion of GT with NF at each hospital, by volume and over time.

RESULTS

40,348 patients were identified across 40 hospitals. Most patients were male (53.8%), non-Hispanic white (49.5%) and publicly-insured (60.4%). Rates of NF by hospital varied significantly from 4.2 to 75.2% (p < 0.001), though were not associated with geographic region (p = 0.088). Rates of NF decreased from 42.8% in 2008 to 14.2% in 2018, with a mean annual rate of change of - 3.07% (95% CI - 3.53, - 2.61). This trend remained when stratifying hospitals into volume quartiles.

CONCLUSION

There is significant practice variation in performing NF. Regardless of volume, the rate of NF is also decreasing. Objective NF outcome measurements are needed to standardize the management of long-term enteral access in this population.

Tetrahydrocurcumin ameliorates homocysteine-mediated mitochondrial remodeling in brain endothelial cells

Homocysteine (Hcy) causes endothelial dysfunction by inducing oxidative stress in most neurodegenerative disorders. This dysfunction is highly correlated with mitochondrial dynamics such as fusion and fission. However, there are no strategies to prevent Hcy-induced mitochondrial remodeling. Tetrahydrocurcumin (THC) is an anti-inflammatory and anti-oxidant compound. We hypothesized that THC may ameliorates Hcy-induced mitochondria remodeling in mouse brain endothelial cells (bEnd3) cells. bEnd3 cells were exposed to Hcy treatment in the presence or absence of THC. Cell viability and autophagic cell death were measured with MTT and MDC staining assay. Reactive oxygen species (ROS) production was determined using DCFH-DA staining by confocal microscopy. Autophagy flux was assessed using a conventional GFP-microtubule-associated protein 1 light chain 3 (LC3) dot assay. Interaction of phagophore marker LC-3 with mitochondrial receptor NIX was observed by confocal imaging. Mitochondrial fusion and fission were evaluated by western blot and RT-PCR. Our results demonstrated that Hcy resulted in cell toxicity in a dose-dependent manner and supplementation of THC prevented the detrimental effects of Hcy on cell survival. Furthermore, Hcy also upregulated fission marker (DRP-1), fusion marker (Mfn2), and autophagy marker (LC-3). Finally, we observed that Hcy activated mitochondrial specific phagophore marker (LC-3) and co-localized with the mitochondrial receptor NIX, as viewed by confocal microscopy. Pretreatment of bEnd3 with THC (15 μM) ameliorated Hcy-induced oxidative damage, mitochondrial fission/fusion, and mitophagy. Our studies strongly suggest that THC has beneficial effects on mitochondrial remodeling and could be developed as a potential therapeutic agent against hyperhomocysteinemia (HHcy) induced mitochondrial dysfunction.

Inhibition of MMP-9 attenuates hypertensive cerebrovascular dysfunction in Dahl salt-sensitive rats

Hypertensive cerebropathy is a pathological condition associated with cerebral edema and disruption of the blood-brain barrier. However, the molecular pathways leading to this condition remains obscure. We hypothesize that MMP-9 inhibition can help reducing blood pressure and endothelial disruption associated with hypertensive cerebropathy. Dahl salt-sensitive (Dahl/SS) and Lewis rats were fed with high-salt diet for 6 weeks and then treated without and with GM6001 (MMP inhibitor). Treatment of GM6001 (1.2 mg/kg body weight) was administered through intraperitoneal injections on alternate days for 4 weeks. GM6001 non-administered groups were given vehicle (0.9% NaCl in water) treatment as control. Blood pressure was measured by tail-cuff method. The brain tissues were analyzed for oxidative/nitrosative stress, vascular MMP-9 expression, and tight junction proteins (TJPs). GM6001 treatment significantly reduced mean blood pressure in Dahl/SS rats which was significantly higher in vehicle-treated Dahl/SS rats. MMP-9 expression and activity was also considerably reduced in GM6001-treated Dahl/SS rats, which was otherwise notably increased in vehicle-treated Dahl/SS rats. Similarly MMP-9 expression in cerebral vessels of GM6001-treated Dahl/SS rats was also alleviated, as devised by immunohistochemistry analysis. Oxidative/nitrosative stress was significantly higher in vehicle-treated Dahl/SS rats as determined by biochemical estimations of malondialdehyde, nitrite, reactive oxygen species, and glutathione levels. RT-PCR and immunohistochemistry analysis further confirmed considerable alterations of TJPs in hypertensive rats. Interestingly, GM6001 treatment significantly ameliorated oxidative/nitrosative stress and TJPs, which suggest restoration of vascular integrity in Dahl/SS rats. These findings determined that pharmacological inhibition of MMP-9 in hypertensive Dahl-SS rats attenuate high blood pressure and hypertension-associated cerebrovascular pathology.

Homocysteine Induced Cerebrovascular Dysfunction: A Link to Alzheimer's Disease Etiology

A high serum level of homocysteine, known as hyperhomocystenemia (HHcy) is associated with vascular dysfunction such as altered angiogenesis and increased membrane permeability. Epidemiological studies have found associations between HHcy and Alzheimer’s disease (AD) progression that eventually leads to vascular dementia (VaD). VaD is the second most common cause of dementia in people older than 65, the first being AD. VaD affects the quality of life for those suffering by drastically decreasing their cognitive function. VaD, a cerebrovascular disease, generally occurs due to cerebral ischemic events from either decreased perfusion or hemorrhagic lesions. HHcy is associated with the hallmarks of dementia such as tau phosphorylation, Aβ aggregation, neurofibrillary tangle (NFT) formation, neuroinflammation, and neurodegeneration. Previous reports also suggest HHcy may promote AD like pathology by more than one mechanism, including cerebral microangiopathy, endothelial dysfunction, oxidative stress, neurotoxicity and apoptosis. Despite the corelations presented above, the question still exists – does homocysteine have a causal connection to AD? In this review, we highlight the role of HHcy in relation to AD by discussing its neurovascular effects and amelioration with dietary supplements. Moreover, we consider the studies using animal models to unravel the connection of Hcy to AD.

Mitochondrial mitophagic mechanisms of myocardial matrix metabolism and remodelling

High levels of homocysteine (Hcy), known as hyperhomocysteinmia (HHcy), are correlated with an increase in extracellular matrix remodelling (ECM) via the matrix metalloproteinases (MMPs) and plasminogen/plasmin system. This results in an increase deposition of collagen that leads to endothelial-myocyte (EM) and myocyte-myocyte (MM) uncoupling; the physiological consequences are a plethora of cardiovascular pathologies. Homocysteine-induced increase in intracellular and mitochondrial Ca(2+) plays an important role in increasing reactive oxygen species (ROS) within mitochondria and instigating mitophagy within the cell. This occurs via several Hcy-mitigated processes: agonizing N-methyl-d-aspartate receptor-1 (NMDA-R1), decreasing expression of peroxisome proliferator activator receptor (PPAR) [thereby increasing oxidation], impairing Ca(2+) handling via Na(+)/Ca(2+) exchanger (NCX1) and Sarco endoplasmic reticulum Ca(2+) ATPase (SERCA-2a). The end result is an increase in ROS that directly or indirectly lead to MMP activation within mitochondria or the cytoplasm. Hcy induces a mitochondrial permeability transition that allows MMPs to be released from mitochondria thereby metabolizing matrix and impairing cardiac function. Further work remains to be elucidated concerning the specific mitochondrial mitophagic mechanisms under which matrix metabolism and remodelling occurs. Moreover, the therapeutic implications of NMDA and PPAR ligands are some promise to patient.

Homocysteine mediated decrease in bone blood flow and remodeling: role of folic acid

Deficiencies in folate lead to increased serum concentrations of homocysteine (Hcy), which is known as hyperhomocysteinemia (HHcy), is associated with bone disorders. Although, Hcy accumulates collagen in bone and contribute to decrease in bone strength. The mechanism of Hcy induced bone loss and remodeling is unclear. Therefore, the present study was aimed to determine the role of folic acid (FA) in genetically HHcy-associated decrease in bone blood flow and remodeling. Wild type (WT) and cystathionine-β-synthase heterozygous (CBS+/-) mice were used in this study and supplemented with or without FA (300 mg/kg, Hcy reducing agent) in drinking water for 6 weeks. The tibial bone blood flow was measured by laser Doppler and ultrasonic flow probe method. The tibial bone density (BD) was assessed by dual energy X-ray absorptiometry. The bone homogenates were analyzed for oxidative stress, NOX-4 as oxidative marker and thioredoxin-1 (Trx-1) as anti-oxidant marker, bone remodeling (MMP-9) and bio-availability of nitric oxide (eNOS/iNOS/NO) by Western blot method. The results suggested that there was decrease in tibial blood flow in CBS+/- mice. The BD was also reduced in CBS+/- mice. There was an increase in NOX-4, iNOS, MMP-9 protein as well as MMP-9 activity in CBS+/- mice and decrease in Trx-1, eNOS protein levels, in part by decreasing NO bio-availability in CBS+/- mice. Interestingly, these effects were ameliorated by FA and suggested that FA supplementation may have therapeutic potential against genetically HHcy induced bone loss.

Hyperhomocysteinemia decreases bone blood flow

Elevated plasma levels of homocysteine (Hcy), known as hyperhomocysteinemia (HHcy), are associated with osteoporosis. A decrease in bone blood flow is a potential cause of compromised bone mechanical properties. Therefore, we hypothesized that HHcy decreases bone blood flow and biomechanical properties. To test this hypothesis, male Sprague–Dawley rats were treated with Hcy (0.67 g/L) in drinking water for 8 weeks. Age-matched rats served as controls. At the end of the treatment period, the rats were anesthetized. Blood samples were collected from experimental or control rats. Biochemical turnover markers (body weight, Hcy, vitamin B12, and folate) were measured. Systolic blood pressure was measured from the right carotid artery. Tibia blood flow was measured by laser Doppler flow probe. The results indicated that Hcy levels were significantly higher in the Hcy-treated group than in control rats, whereas vitamin B12 levels were lower in the Hcy-treated group compared with control rats. There was no significant difference in folate concentration and blood pressure in Hcy-treated versus control rats. The tibial blood flow index of the control group was significantly higher (0.78 ± 0.09 flow unit) compared with the Hcy-treated group (0.51 ± 0.09). The tibial mass was 1.1 ± 0.1 g in the control group and 0.9 ± 0.1 in the Hcy-treated group. The tibia bone density was unchanged in Hcy-treated rats. These results suggest that Hcy causes a reduction in bone blood flow, which contributes to compromised bone biomechanical properties.

Hydrogen sulfide mitigates transition from compensatory hypertrophy to heart failure

We reported previously that although there is disruption of coordinated cardiac hypertrophy and angiogenesis in transition to heart failure, matrix metalloproteinase (MMP)-9 induced antiangiogenic factors play a vital role in this process. Previous studies have shown the cardioprotective role of hydrogen sulfide (H₂S) in various cardiac diseases, but its role during transition from compensatory hypertrophy to heart failure is yet to be unveiled. We hypothesize that H₂S induces MMP-2 activation and inhibits MMP-9 activation, thus promoting angiogenesis, and mitigates transition from compensatory cardiac hypertrophy to heart failure. To verify this, aortic banding (AB) was created to mimic pressure overload in wild-type (WT) mice, which were treated with sodium hydrosulfide (NaHS, H₂S donor) in drinking water and compared with untreated control mice. Mice were studied at 3 and 8 wk. In the NaHS-treated AB 8 wk group, the expression of MMP-2, CD31, and VEGF was increased while the expression of MMP-9, endostatin, angiostatin, and tissue inhibitor of matrix metalloproteinase (TIMP)-3 was decreased compared with untreated control mice. There was significant reduction in fibrosis in NaHS-treated groups. Echocardiograph and pressure-volume data revealed improvement of cardiac function in NaHS-treated groups over untreated controls. These results show that H₂S by inducing MMP-2 promotes VEGF synthesis and angiogenesis while it suppresses MMP-9 and TIMP-3 levels, inhibits antiangiogenic factors, reduces intracardiac fibrosis, and mitigates transition from compensatory hypertrophy to heart failure.

Electrical stimulation of cardiomyocytes activates mitochondrial matrix metalloproteinase causing electrical remodeling

Cardiac arrhythmias, instigated by mechanical and electrical remodeling, are associated with activation of extracellular matrix metalloproteinases (MMPs). However, the connection between intracellular MMPs activation and arrhythmogenesis is not well established. Previously, we determined localization of MMP in the mitochondria using confocal microscopy. We tested the hypothesis that electrical pacing induces the activation of mitochondrial MMP (mtMMP) and is associated with myocyte mechanical dysfunction. Myocytes were isolated and field stimulated at 1 and 4 Hz. Myocyte mechanics and calcium transient was studied using Ion-Optix system. Mitochondrial MMP-9 activation was evaluated using zymography. There was a 25% increase in 1 Hz and 40% increase in 4 Hz stimulation. We observed an increase in mtMMP activation with increase in electrical pacing compared to 0 Hz with a significant increase (p<0.05, n=3). Field stimulation at 4 Hz decreased cell re-lengthening. The levels of calcium transient were reduced with increase in contraction frequency. We conclude that electrical stimulation activates mtMMP-9 that is associated with myocyte mechanical dysfunction.

Cardiac specific deletion of N-methyl-d-aspartate receptor 1 ameliorates mtMMP-9 mediated autophagy/mitophagy in hyperhomocysteinemia

Autophagy is an important process in the pathogenesis of cardiovascular diseases; however, the proximal triggers for mitochondrial autophagy were unknown. The N-methyl-d-aspartate receptor 1 (NMDA-R1) is a receptor for homocysteine (Hcy) and plays a key role in cardiac dysfunction. Cardiac-specific deletion of NMDA-R1 has been shown to ameliorate Hcy-induced myocyte contractility. Hcy activates mitochondrial matrix metalloproteinase-9 (mtMMP-9) and induces translocation of connexin-43 (Cxn-43) to the mitochondria (mtCxn-43). We sought to show cardiac-specific deletion of NMDA-R1 mitigates Hcy-induced mtCxn-43 translocation, mtMMP-9-mediated mtCxn-43 degradation, leading to mitophagy, in part, by decreasing mitochondrial permeability (MPT). Cardiac-specific knockout (KO) of NAMDA-R1 was generated using the cre/lox approach. The myocyte mitochondria were isolated from wild type (WT), WT + Hcy (1.8 g of DL-Hcy/L in the drinking water for 6 weeks), NMDA-R1 KO + Hcy, and NR1(fl/fl)/Cre (NR1(fl/fl)) genetic control mice. Mitochondrial respiratory capacity and MPT were measured by fluorescence-dye methods. The mitochondrial superoxide and peroxinitrite levels were detected by confocal microscopy using Mito-SOX and dihydrorhodamine-123. The mtMMP-9 activity and expression were detected by zymography and RT-PCR analyses. The mtCxn-43 translocation was detected by confocal microscopy. The degradation of mtCxn-43 and LC3-I/II (a marker of autophagy) were detected by Western blot. These results suggested that Hcy enhanced intramitochondrial nitrosative stress in myocytes. There was a robust increase in mtMMP-9 activity. An increase in translocation and degradation of mtCxn-43 was also noted. These increases led to mitophagy. The effects were ameliorated by cardiac-specific deletion of NMDA-R1. We concluded that HHcy increased mitochondrial nitrosative stress, thereby activating mtMMP-9 and inciting the degradation of mtCxn-43. This led to mitophagy, in part, by activating NMDA-R1. The findings of this study will lead to therapeutic ramifications for mitigating cardiovascular diseases by inhibiting the mitochondrial mitophagy and NMDA-R1 receptor.

MMP-2/TIMP-2/TIMP-4 versus MMP-9/TIMP-3 in transition from compensatory hypertrophy and angiogenesis to decompensatory heart failure

Although matrix metalloproteinase (MMPs) and tissue inhibitor of metalloproteinase (TIMPs) play a vital role in tumour angiogenesis and TIMP-3 caused apoptosis, their role in cardiac angiogenesis is unknown. Interestingly, a disruption of co-ordinated cardiac hypertrophy and angiogenesis contributed to the transition to heart failure, however, the proteolytic and anti-angiogenic mechanisms of transition from compensatory hypertrophy to decompensatory heart failure were unclear. We hypothesized that after an aortic stenosis MMP-2 released angiogenic factors during compensatory hypertrophy and MMP-9/TIMP-3 released anti-angiogenic factors causing decompensatory heart failure. To verify this hypothesis, wild type (WT) mice were studied 3 and 8 weeks after aortic stenosis, created by banding the ascending aorta in WT and MMP-9-/- (MMP-9KO) mice. Cardiac function (echo, PV loops) was decreased at 8 weeks after stenosis. The levels of MMP-2 (western blot) increased at 3 weeks and returned to control level at 8 weeks, MMP-9 increased only at 8 weeks. TIMP-2 and -4 decreased at 3 and even more at 8 weeks. The angiogenic VEGF increased at 3 weeks and decreased at 8 weeks, the anti-angiogenic endostatin and angiostatin increased only at 8 weeks. CD-31 positive endothelial cells were more intensely labelled at 3 weeks than in sham operated or in 8 weeks banded mice. Vascularization, as estimated by x-ray angiography, was increased at 3 weeks and decreased at 8 weeks post-banding. Although the vast majority of studies were performed on control WT mice only, interestingly, MMP9-KO mice seemed to have increased vascular density 8 weeks after banding. These results suggested that there was increase in MMP-2, decrease in TIMP-2 and -4, increase in angiogenic factors and vascularization in compensatory hearts. However, in decompensatory hearts there was increase in MMP-9, TIMP-3, endostatin, angiostatin and vascular rarefaction.

Hydrogen sulfide protects against vascular remodeling from endothelial damage

Remodeling by its very nature implied synthesis and degradation of extracellular matrix (ECM) proteins. Although oxidative stress, matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) have been implicated in vascular remodeling, the differential role of MMPs versus TIMPs and oxidative stress in vascular remodeling was unclear. TIMP-3 induced vascular cell apoptosis, therefore, we hypothesized that during vascular injury TIMP-3, MMP-9 and -12 (elastin-degrading MMP) were increased, whereas MMP-2 (constitutive MMP) and TIMP-4 (cardioprotective TIMP) decreased. Because of the potent anti-oxidant, vasorelaxing, anti-hypertensive agent, hydrogen sulfide (H2S) was used to mitigate the vascular remodeling due to the differential expression of MMP and TIMP. Carotid artery injury was created by inserting a PE-10 catheter and rotating several times before pulling out. The insertion hole was sealed. Mice were grouped: wild type (WT), wild-type damaged artery (WTD), WT+NaHS (sodium hydrogen sulfide, precursor of H2S) treatment (30 µmol/L in drinking water/6 weeks) and WTD+NaHS treatment. Carotid arteries were analyzed for oxidative stress and remodeling, by measuring super oxide dismutase-1 (SOD1), p47 (NADPH oxidase subunit), nitrotyrosine, MMPs and TIMPs by in situ immunolabeling and by Western blot analyses. The results suggested robust increase in p47, nitrotyrosine, MMP-9, MMP-12, TIMP-3 and decrease in SOD1 and MMP-2 levels in the injured arteries. The treatment with H2S ameliorated these effects. We concluded that p47, TIMP-3, MMP-9 and -12 were increased where as SOD-1, MMP-2 and TIMP-4 were decreased in the injured arteries. The treatment with H2S mitigated the vascular remodeling by normalizing the levels of redox stress, MMPs and TIMPs.

Hydrogen sulfide mitigates matrix metalloproteinase-9 activity and neurovascular permeability in hyperhomocysteinemic mice

An elevated level of homocysteine (Hcy), known as hyperhomocysteinemia (HHcy), was associated with neurovascular diseases. At physiological levels, hydrogen sulfide (H(2)S) protected the neurovascular system. Because Hcy was also a precursor of hydrogen sulfide (H(2)S), we sought to test whether the H(2)S protected the brain during HHcy. Cystathionine-beta-synthase heterozygous (CBS+/-) and wild type (WT) mice were supplemented with or without NaHS (30 microM/L, H(2)S donor) in drinking water. Blood flow and cerebral microvascular permeability in pial vessels were measured by intravital microscopy in WT, WT+NaHS, CBS-/+ and (CBS-/+)+NaHS-treated mice. The brain tissues were analyzed for matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) by Western blot and RT-PCR. The mRNA levels of CBS and cystathionine gamma lyase (CSE, enzyme responsible for conversion of Hcy to H(2)S) genes were measured by RT-PCR. The results showed a significant increase in MMP-2, MMP-9, TIMP-3 protein and mRNA in CBS (-/+) mice, while H(2)S treatment mitigated this increase. Interstitial localization of MMPs was also apparent through immunohistochemistry. A decrease in protein and mRNA expression of TIMP-4 was observed in CBS (-/+) mice. Microscopy data revealed increase in permeability in CBS (-/+) mice. These effects were ameliorated by H(2)S and suggested that physiological levels of H(2)S supplementation may have therapeutic potential against HHcy-induced microvascular permeability, in part, by normalizing the MMP/TIMP ratio in the brain.

Differential expression of Gs in a murine model of homocysteinemic heart failure

High plasma homocysteine levels are a known risk factor in heart failure and sudden cardiac death. The G proteins, G(s) (stimulatory) and G(i) (inhibitory), are involved in calcium regulation; overexpression has pathological consequences. The aims of this study were to examine the differential expression of G(s) G protein and G(i) in the hearts of hyperhomocysteinemic (Hhcy) mice, and to determine if homocysteine (Hcy) acts as an agonist in cell culture to mediate the change in G protein isoforms. To create Hhcy, heterozygous cystathionine-beta-synthase (CBS) knockout (KO) mice were used. Mice were sacrificed, hearts were excised, cardiac tissue homogenates were prepared, and Western blots were performed. The results suggested that G(s) G protein was downregulated in cardiac tissue of heterozygous CBS KO mice to 46% that of control hearts. However, the intracellular G(i) G protein content remained the same in heterozygous CBS KO mice. Transformed cardiomyocyte HL-1 cells were treated with varying concentrations of homocysteine. The results suggested no detectable differential G(s) and G(i) expression. This suggested that Hcy did not act as an agonist in vitro to alter G protein content, but that Hcy produced some other in vivo effects to incur these results.