Pentraxin 3

To elucidate the mechanism of Pentraxin 3 (PTX3) in the pathogenesis of psoriasiform dermatitis using Ptx3-knockout (Ptx3-KO) background mice.

An Imiquimod (IMQ)-induced murine psoriatic model was created using Ptx3-KO (Ptx3^-/-) and wild-type (Ptx3^+/+) mice. Skin lesion severity and expression of inflammatory mediators (IL-6 and TNFα) were assessed using PASI score and ELISA, respectively. Cutaneous tissues from the two mice groups were subjected to histological analyses, including HE staining, Masson staining, and Immunohistochemistry (IHC). The PTX3, iNOS, COX2, and Arg1 expressions were quantified and compared between the two groups. We used RNA-seq to clarify the underlying mechanisms of the disease. Flow cytometry was used to analyze systemic Th17 cell differentiation and macrophage polarization.

The psoriatic region exhibited a higher PTX3 expression than the normal cutaneous area. Moreover, PTX3 was upregulated in HaCaT cells post-TNFα stimulation. Upon IMQ stimulation, Ptx3^-/- mice displayed a lower degree of the psoriasiform dermatitis phenotype compared to Ptx3^+/+ mice. Consistent with the RNA-seq results, further experiments confirmed that compared to the wild-type group, the PTX3-KO group exhibited a generally lower IL-6, TNFα, iNOS, and COX2 expression and a contrasting trend in macrophage polarization. However, no significant difference in Th17 cell activation was observed between the two groups.

This study revealed that PTX3 was upregulated in psoriatic skin tissues and TNFα-stimulated HaCaT cells. We also discovered that PTX3 deficiency in mice ameliorated the psoriasiform dermatitis phenotype upon IMQ stimulation. Mechanistically, PTX3 exacerbates psoriasiform dermatitis by regulating macrophage polarization rather than Th17 cell differentiation.

Although pentraxin-3 holds promise as a diagnosis/prognosis biomarker of microbial infections and lung cancer, its analysis in human serum can be constrained by matrix effects caused by high abundance proteins - human serum albumin and immunoglobulin G. Aqueous biphasic systems composed of polymers and citrate buffer are here proposed as a serum pretreatment step to improve the accuracy of pentraxin-3 analysis. Binodal curves were determined to identify the compositions required to form two phases and to correlate the polymers' properties and performance in serum pretreatment and biomarker extraction. Aqueous biphasic systems were evaluated regarding their ability to deplete human serum albumin and immunoglobulin G at the interphase. Polymers of relatively high to intermediate hydrophobicity were unveiled as efficient components to deplete high abundance serum proteins. Considering the possibility to extract pentraxin-3 from human serum into the polymer-rich phase, the system composed of polyethylene glycol with a molecular weight of 1000 g·mol^-1 simultaneously achieved >93 % of human serum albumin and immunoglobulin G depletion and complete biomarker extraction. The accuracy of analysis of pretreated human serum by enzyme-linked immunosorbent assays outperformed that of a non-pretreated sample, with a relative error of 0.8 % compared to 14.6 %, contributing to boost pentraxin-3 usefulness as a biomarker.