Expression Of Nitric Oxide Synthase, Vascular Cell Adhesion Molecule and C- Reactive Protein Receptor In Sickle Cell Leucocytes: Relationship With Chronic Inflammation

Chronic and acute inflammatory phenomenon’s can contribute to activate several cells types and may play important role in the steady- and crisis-states of sickle cell anemia (HbSS) patients. Under normal circumstances, the nitric oxide synthase (NOS) constitutively produces low levels of nitric oxide (NO) that are important in the maintenance of vascular homeostasis, but in HbSS this balance is disrupted, mainly because the lack of arginine and the depletion of NO. This molecule also has an anti-inflammatory role in the vascular system and the state of resistance of NO can lead to deregulation of several other factors and interaction with many molecules. The aim of this study was correlate the expression of NOS, vascular cell adhesion molecule (VCAM), c-reactive protein receptor (rCRP) genes and biochemical profile of HbSS patients.

We studied 21 HbSS patients from Northeast Brazil, at steady state and were transfusion free. Blood samples were obtained during regular clinical visits. The expression of NOS, VCAM and rCRP genes were performed by real time PCR with Taqman assays from leucocytes RNA in trizol reagent. Serum biochemical analysis was determined using commercially available biochemical kits. The study was approved by the FIOCRUZ ethical committee and informed consents were signed by patients or official responsible.

Our results showed a positive correlation among the expression of NOS and VCAM (p= 0.031, r=0.525), NOS and rCRP (p< 0.001, r=0.816) and VCAM and rCRP (p=0.003, r=0.659). Analyses of biochemical profile of HbSS individuals showed a correlation of NOS and serum calcium (p=0.044, r=0.456) as well as NOS and alkaline phosphatase (p=0.036, r=0.472).

Discussion and Conclusion

In this study, the correlation among genetic expression of NOS, VCAM and rCRP molecules suggests how factors involved to inflammation in HbSS are linked. In response to inflammation, the liver releases a variety of acute phase proteins. One such product, CRP, serves as a dominating diagnostic marker of inflammation. Chronic inflammatory reflects in the up-regulation of VCAM and VOC susceptibility, can increase the release of alkaline phosphatase, as well as deregulation of NOS expression due to impaired constitutive NOS activity with loss of endothelial NOS dimerization, increased NO scavenging by plasma hemoglobin and superoxide, increased arginase activity, and depleted intravascular nitrite reserves. Also, NOS couples electron flux for NO production by binding calmodulin, which is calcium-dependent, which explain the positive correlation between NOS and serum calcium. Furthermore, additional studies will elucidate the mechanism involved with the interaction of this complex network of molecule and the endothelial activation and dysfunction described in the pathophysiology of HbSS chronic and acute inflammatory.

No relevant conflicts of interest to declare.