DISCUSSION
To best of our knowledge this is the first study about relationship between FMD response (impaired endothelial response) and blood parameters in patients with pRP. On the other hand this is the first report about relationship between impaired endothelial response and MCP-1 levels in pRP. Our results indicated that patients with pRP have higher impaired endothelial to ischemia. The incremental levels of serum WBC, MPV, MCP-1 and fibrinogen values were detected in pRP group. Moreover, moderate direct correlation was found between abnormal FMD response and serum MCP-1 values.
The impaired endothelial dysfunction demonstrated in both primary and secondary RP in previous studies. Furthermore it was shown that microvascular derangement was found as associated with endothelial dysfunction in RP patients 11,12 . The endothelium has an important role in the regulation of vascular response against blood flow‐associated shear stress and ischemia-reperfusion events. Insufficient flow-mediated vasorelaxation response is an indicator for increased vascular disease 13 . The dilation response of the brachial artery after a 4-5 minutes ischemic period is a reliable non-invasive assessment method for the evaluation of endothelium functions. The post-ischemic brachial artery dilatation with equal to or more than 5% of normal diameter is accepted as normal endothelial functions. Additionally, dilatation with lower than 5% of diameter is accepted as impaired endothelial functions 9,14 . The FMD response was studied in patients with RP. Flavahan indicated as FMD response is normal in pRP and it was added that cold induced disruption of arteriovenous connections in RP cases, can lead to digital artery spasm 15 . Mavrikakis et al. studied FMD in patients with sRP and they detected abnormal FMD response in these patients. Additionally, they found that ascorbic acid does not reverse endothelial vasomotor dysfunction in their study 16 . Klein-Weigel et al. investigate the seasonal variations in patients with RP and they did not show abnormal FMD response in pRP 17 . However most of the previous reports were conducted with mall RP populations. Although our results indicated that abnormal FMD response can detected 5 (17%) of 30 healthy individuals, the abnormal FMD was detected at 30 (70%) of 43 pRP patients.
The routine blood parameters were investigated for several kinds of vascular diseases 18 . Platelet indices were investigated in vasospastic disorders detected with cold stimulation test by Kadan et al. 19 . They found that the relationship between severity of disease and MPV. Shemirani et al. found independent relationship between pRP and higher serum MPV levels20 . Another study higher MPV was suggested as triggering factor for pRP 21 . In same study WBC levels were found as insignificant predictor in same study. Lau et al. was found increased white blood cell activation in patients with RP22 . Our findings supported that MPV and WBC levels in patients with pRP. Plasma fibrinogen is another laboratory parameter that investigated in vasospatic disorders. Splenger et al. concluded as increased plasma fibrinogen levels in patients with RP are related with disrupted distal microcirculation 23 . Similarly, higher fibrinogen levels found as associated with plasma fibrin clots displaying impaired lysability and increased endothelial damage in pRP by Żuk et al. 24 . In our study higher fibrinogen levels were detected in pRP patients.
MCP-1 is an important potent regulatory chemokine that is responsible for the migration and the infiltration of monocytes. The ischemia, oxidative stress, released cytokines, or growth factors triggers the biological activity of MCP-1 and leads to infiltration of monocytes/macrophages. Rajagopalan et al. investigated to MCP-1 levels in sRP and pRP and they found that MCP-1 levels were higher in sRP when compared with primary type. However, they did not compare the MCP-1 levels with healthy controls and did not investigate the relation with endothelial response 25 . MCP-1 was suspected to pathogenesis of vasospastic outcomes of diseases that presented with sRP26,27 . However, the literature includes insufficient reports about the relationship between impaired endothelial function and MCP-1 levels in pRP. Furthermore, another insufficiency is about the differences between pRP and normal population in regards to MCP-1 levels. Our results indicated that MCP-1 levels are higher in patients with pRP and these results revealed a relation between impaired endothelial functions and serum MCP-1 levels.
In conclusion, our findings demonstrated that MPV, WBC, fibrinogen, and MCP-1 levels were higher in pRP patients when compare with healthy control. It seems to be that increased MCP-1 values were related to abnormal FMD response in pRP group. These results might be helpful for the establishment of the pathophysiology of the RP.
Limitations of Study
The main limitation of the study is concerning about small sample size. Although previous literature has present findings with smaller patient groups, the comprehensive cohorts are necessary for obtaining powerful and exact results. The second limitation is concerning the determination of endothelial response with a single method (FMD). The endothelial response should be confirmed with other techniques to present more clarified findings. The third limitation is related to the nature of the disease. If any underlying disease cannot be detected responsible for RP then it called primary RP. However, there is multifactorial etiology for RP and it is possible to skip diagnosis.
Acknowledgement
Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Competing Interest: The authors declare no conflict of interest.