Impaired vascular endothelium-dependent relaxation in Henoch-Schönlein purpura

Flow-Mediated Dilatation of the Brachial Artery for Assessing Endothelial Dysfunction in Children with Moyamoya Disease

BACKGROUND

Moyamoya disease is a progressive, steno-occlusive arteriopathy involving the internal carotid artery and its branches and causing recurrent stroke episodes in children. Patients with moyamoya disease may be more susceptible to influences that cause endothelial dysfunction. We evaluated whether flow-mediated dilatation (FMD) of the brachial artery is useful for assessing endothelial dysfunction in children with moyamoya disease.

METHODS

This prospective observational study included 30 children with moyamoya disease and 30 controls. After anesthesia induction, a blood pressure cuff was applied to the forearm and inflated to a pressure that was 50 mm Hg above the baseline systolic blood pressure for 5 min. From 30 s before to 2 min after deflation, the brachial artery diameter was recorded on ultrasound. The increase in internal diameter was expressed as the percentage of the baseline diameter.

RESULTS

Fifty-nine patients were analyzed. Baseline brachial artery diameters in the moyamoya and control groups were 3.00 and 3.37 mm, respectively (p = 0.004; difference, 0.38; 95% CI 0.12-0.63), while those after deflation were 3.06 and 3.48 mm, respectively (p = 0.003; difference, 0.42; 95% CI 0.15-0.68). The percent change of the baseline diameter value was 4.0% in the disease group and 8.3% in the control group (p = 0.10). There was a group and time interaction for brachial artery diameter (p = 0.01; main effect of group, p = 0.009; main effect of time, p = 0.007).

CONCLUSION

FMD of the brachial artery may not be enough for determining endothelial dysfunction under general anesthesia in children with moyamoya disease.

Endothelial function in children with a history of henoch schonlein purpura

BACKGROUND

Although Henoch-Schonlein purpura (HSP) is the most common form of systemic vasculitis in children, the long term effect of HSP on endothelial function is still not clear. The aim of our study was to evaluate the long term effect of HSP on endothelial function in children and adolescents.

METHODS

This research was an observational prospective study. The study group comprised of 19 children diagnosed with HSP. The minimum interval between the diagnosis with HSP and endothelial testing was 5 months. Endothelial function evaluation was assessed by a noninvasive technology named peripheral arterial tonometry, using an EndoPAT™ device. This method measures blood flow in the limb, in response to arterial occlusion, and calculates a Reactive Hyperemic Index (RHI) as an index of endothelial function. RHI values of the study group were compared to those of a known control group.

RESULTS

Nineteen children and adolescents with HSP underwent endothelial function studies. Endothelial function was compared to that of a known control group comprising of 23 healthy children and adolescents. The two groups had similar characteristics, including age, male to female ratio, height, weight and BMI. Mean RHI was 1.81 in the study group, and 1.87 in the control group (p = 0.18). Linear regression of the study group, showed a positive correlation between the time interval from HSP diagnosis to participation in the study, and between the RHI value (r = 0.542, p = 0.016). RHI levels were significantly higher in patients who had endothelial function measured more than 6 years since the diagnosis of HSP compared with those patients with less than 6 years follow up (1.98 + 0.74 vs. 1.38 ± 0.43 P = 0.037).

CONCLUSIONS

These results suggest that HSP causes short term endothelial dysfunction that improves with time.

Requirement of argininosuccinate lyase for systemic nitric oxide production

Nitric oxide (NO) is crucial in diverse physiological and pathological processes. We show that a hypomorphic mouse model of argininosuccinate lyase (encoded by Asl) deficiency has a distinct phenotype of multiorgan dysfunction and NO deficiency. Loss of Asl in both humans and mice leads to reduced NO synthesis, owing to both decreased endogenous arginine synthesis and an impaired ability to use extracellular arginine for NO production. Administration of nitrite, which can be converted into NO in vivo, rescued the manifestations of NO deficiency in hypomorphic Asl mice, and a nitric oxide synthase (NOS)-independent NO donor restored NO-dependent vascular reactivity in humans with ASL deficiency. Mechanistic studies showed that ASL has a structural function in addition to its catalytic activity, by which it contributes to the formation of a multiprotein complex required for NO production. Our data demonstrate a previously unappreciated role for ASL in NOS function and NO homeostasis. Hence, ASL may serve as a target for manipulating NO production in experimental models, as well as for the treatment of NO-related diseases.

Circulating endothelial microparticles in children with Henoch-Schönlein purpura; preliminary results

The aim of this study was to investigate the levels of circulating endothelial microparticles (EMPs) in children with HSP and to determine whether there was a difference between patients with nephritis and those without nephritis. Twenty patients with HSP aged between 2.5 and 15 and 10 age-and sex-matched healthy controls were enrolled in the study. The HSP group was divided into two groups, including patients with nephritis (n = 9) and those without nephritis (n = 11). In all groups, circulating EMPs were enumerated by flow cytometry, after staining platelet-free plasma with PE-conjugated anti-CD144. At the same time, human umbilical vein endothelial cells (HUVEC) were incubated with the platelet-free plasma of patients with HSP and that of the control group. Then, circulating EMPs were counted in HUVEC supernatant incubated with the platelet-free plasma of patients and control groups, after staining the supernatant with PE-conjugated anti-CD146. Circulating EMPs were significantly higher in both the active and the remission period of the patient groups compared with the control subjects. In the patient group, there were no statistically significant differences in the level of circulating EMPs between patients with nephritis and those without nephritis. Both CD144 and 146+EMP in patients with HSP nephritis in the active period were substantially higher than in those remissions. CD144+EMP in the active period were substantially higher than in the remission period in patients without nephritis. We detected that circulating EMPs increased in patients with HSP in both active and remission periods. Although clinical and laboratory findings return to normal in the remission period, the increased circulating EMPs may show that the subclinical inflammatory process is continuous. We think that circulating EMPs could be used as a surrogate marker for subclinical inflammation in HSP.

Henoch-Schonlein purpura: polymorphisms in thrombophilia genes

Henoch-Schonlein purpura (HSP) is a small-sized vasculitis affecting mainly children. Based on the hypothesis that an inherited predilection to hypercoagulability may predispose to HSP or may mark those who develop acute clinical manifestations, we evaluated the possible roles of methylenetetrahydrofolate reductase (MTHFR) gene C677T, factor V (FV) gene G1691A (Leiden), and prothrombin gene G20210A polymorphisms in patients with HSP. Fifty-two HSP patients (32 boys and 20 girls) from different ethnic groups (22 Jews and 30 Arabs) and 104 ethnically matched controls were studied for these three polymorphisms. The frequencies of these mutations for each group, separately and in combinations, are described. The mutation frequencies in the MTHFR, prothrombin and FV genes in HSP patients did not differ from those in controls. In a small number of individuals (n=5) homozygosity for the 677T thermolabile variant of MTHFR was associated with hematuria. To summarise, hypercoagulability does not seem to play a role in HSP. Studies in larger cohorts and possibly inclusion of additional factors may be needed to ascertain whether homozygoty for MTHFR 677T polymorphism can influence disease severity.

Oxalate degrading bacteria: new treatment option for patients with primary and secondary hyperoxaluria?

Current treatment options in patients with primary and secondary hyperoxaluria are limited and do not always lead to sufficient reduction in urinary oxalate excretion. Intestinal oxalate degrading bacteria are capable of degrading oxalate to CO(2) and formate, the latter being further metabolized and excreted via the feces. It is speculated, that both endogenously produced, as well as dietary oxalate can be significantly removed via the intestinal tract. Oxalobacter formigenes, an obligate anaerobic microbe normally found in the intestinal tract has one oxalate degrading enzyme, oxalyl-CoA decarboxylase, which is also found in Bifidobacterium lactis. Other bacteria with possible oxalate degrading potency are lactic acid bacteria, as well as Enterococcus faecalis and Eubacterium lentum. However, specific therapeutic studies on humans are scarce and, except for Oxalobacter, data are not congruent. We found the oral application of Oxalobacter successful in patients with primary hyperoxaluria. However, long-term post-treatment follow-up of 1-2 years showed that constant intestinal colonization is not achieved in most patients. In one patient with constant colonization, urinary oxalate excretion normalized over time. Short-term studies with other bacteria such as lactic acid bacteria did not show a specific reduction in urinary oxalate excretion. O. formigenes might be a promising new therapeutic tool in patients with primary and secondary hyperoxaluria.