In unwounded skin, human keratinocytes (HKs) are in contact with a plasma filtrate. In an acute wound, HKs come in contact with serum for the first time. Because human serum (HS), but not plasma, promotes HK migration, we speculated that a major HK pro-motility factor in vivo comes from serum. In this study, we compared all of the published growth factors (GFs), reported to promote HK migration, with HS. No single GF could duplicate the HK pro-motility activity in HS. Among these GFs, tumor growth factor (TGF)alpha showed the highest HK pro-motility activity, reaching similar to 80% of the activity in HS. The order of potency was: TGF alpha > insulin > EGF > heparin binding (HB)-EGF > IGF-1 > basic fibroblast growth factor > IL-8 > HGF > IL-1 > KGF > TGF beta. Interestingly, the combination of TGF alpha and insulin could duplicate the HK pro-motility activity in HS, although only the TGF alpha, but not insulin, levels increase in serum over plasma. Addition of neutralizing antibodies against TGF alpha to serum or depletion of TGF alpha from serum by immunoprecipitation significantly abolished its HK pro-motility activity. Plasma with added TGF alpha stimulated HK migration that reached more than 80% of the serum stimulation. Since insulin levels are identical between plasma and serum, we propose that TGF alpha is the physiologic HK pro-motility factor in HS.

Vascular endothelial cells (VECs) that line the interiors of blood vessels participate in physiological and inflammatory processes. All skin cell types express the aryl hydrocarbon receptor (AhR), which is involved in the pathogenesis of psoriasis. However, the role of the cutaneous VEC AhR in the pathogenesis of psoriasis remains elusive. In the present study, we found that AhR protein expression and activation were downregulated in psoriatic VECs. Furthermore, cutaneous VEC-specific AhR-knockout (AhR(cVECs-KO)) mice were established. Using imiquimod and IL-23-induced psoriasis models, we found that skin inflammation was exacerbated with excessive neutrophil recruitment in AhR(cVECs-KO) mice. Furthermore, neutrophil neutralization alleviates exacerbated inflammation in imiquimod-treated AhR(cVECs-KO) mice. In addition, cutaneous VECs in AhR(cVECs-KO) mice exhibited increased dilation and activation compared with those in control mice. Finally, AhR-deficient microvascular endothelial cells stimulated by proinflammatory cytokines showed increased ICAM-1 expression in vivo and in vitro, which may have facilitated neutrophil recruitment. In summary, our study demonstrates that AhR in dermal VECs restricts psoriasis development by negatively regulating neutrophil recruitment, thereby providing insight into the pathogenesis of psoriasis.

Psoriasis linkage to 4q28-32 (PSORS9) was initially identified by our genome-wide scan in 61 Chinese families and subsequently supported by a meta-analysis of five genome-wide linkage scans of European populations. In this study, we performed a follow-up analysis of PSORS9 using an additional 90 families and improved marker coverage. Joint analysis of all 151 families obtained significant linkage evidence (HLOD=4.53, nonparametric linkage (NPL) =4.03 (P=0.000003)) at the marker interval D4S2997-D4S3033, and the same was obtained for the analysis of the independent new families (HLOD = 4.33, NPL-3.15 (P = 0.00004)). The linkage evidences from the whole families and the new families exceeded the genome-wide criteria for significant linkage. Furthermore, by performing an ordered subset analysis using mean age at onset as a covariate, we demonstrated that evidence for linkage to PSORS9 is concentrated in the early-onset families and suggested that further study of PSORS9 should focus on early-onset patients. This finding is contradictory to what was found in the Icelandic population and, together with other linkage results, suggests that Chinese and European populations are genetically different for linkage to PSORS9, which may partially explain the influence of ethnic factors on the varying prevalence of psoriasis.

Persistent chronic inflammation and delayed epithelialization lead to stalled healing in diabetic ulcers (DUs). PD-L1 shows anti-inflammatory and proliferative activities in healing defects, whereas its function in DU pathogenesis remains unknown. Lower levels of PD-L1 were found in DU tissues, and exogenous PD-L1 has therapeutic effects in the healing process by accelerating re-epithelialization and attenuating prolonged inflammation, which contributed to the delayed wound closure. We detected the downstream effectors of PD-L1 using transcriptional profiles and screened the interacting proteins using immunoprecipitation in combination with mass spectrometry and coimmunoprecipitation assays. The biological functions of eIF3I-PD-L1. IRS4 axis were tested both in vivo and in vitro. Finally, we validated the expression levels of eIF3I, PD-L1, and IRS4 in DU tissues from human clinical samples by immunohistochemistry staining. Mechanistically, PD-L1 binds to eIF3I and promotes cutaneous diabetic wound healing by downregulating IRS4. These findings identify that the eIF3I-PD-L1.IRS4 axis contributes to wound healing defects, which can serve as a potential therapeutic target in DUs.

Platelet-derived growth factor BB (PDGF-BB) is a Food and Drug Administration (FDA)-approved growth factor, acting as a mitogen and motogen of dermal fibroblasts (DFs), for skin wound healing. The two closely related SH2/SH3 adapter proteins, Nck alpha and Nck beta, connect PDGF-BB signaling to the actin cytoskeleton and cell motility. The mechanism has not been fully understood. In this study, we investigated, side by side, the roles of Nck alpha and Nck beta in PDGF-BB-stimulated DF migration. We found that cells expressing the PDGFR beta-Y751F mutant (preventing Ncka binding) or PDGFR beta-Y1009F mutant (preventing Nckb binding), DF cells isolated from Nck alpha- or Nck beta-knockout mice, and primary human DF cells with RNA interference (RNAi) knockdown of the endogenous Nck alpha or Nck beta all failed to migrate in response to PDGF-BB. Overexpression of the middle SH3 domain of Nck alpha or Nck beta alone in human DFs also blocked PDGF-BB-induced cell migration. However, neither Ncka nor Nck beta was required for the activation of the PDGF receptor, p21-activated protein kinase (Pak1), AKT, extracellular signal-regulated kinase (ERK) 1/2, or p38MAP by PDGF-BB. Although PDGF-BB stimulated the membrane translocation of both Nck alpha and Nck beta, Nck alpha appeared to mediate Cdc42 signaling for filopodium formation, whereas Nck beta mediated Rho signaling to induce stress fibers. Thus, this study has elucidated the independent roles and mechanisms of action of Nck alpha and Nck beta in DF migration, which is critical for wound healing.

Oculocutaneous albinism (OCA) is a heterogeneous and autosomal recessive disorder with hypopigmentation in the eye, hair, and skin color. Four genes, TYR, OCA2, TYRP1, and SLC45A2, have been identified as causative genes for nonsyndromic OCA1-4, respectively. The genetic identity of OCA5 locus on 4q24 is unknown. Additional unknown OCA genes may exist as at least 5% of OCA patients have not been characterized during mutational screening in several populations. We used exome sequencing with a family-based recessive mutation model to determine that SLC24A5 is a previously unreported candidate gene for nonsyndromic OCA, which we designate as OCA6. Two deleterious mutations in this patient, c.591G>A and c.1361insT, were identified. We found apparent increase of immature melanosomes and less mature melanosomes in the patient's skin melanocytes. However, no defects in the platelet dense granules were observed, excluding typical Hermansky-Pudlak syndrome (HPS), a well-known syndromic OCA. Moreover, the SLC24A5 protein was reduced in steady-state levels in mouse HPS mutants with deficiencies in BLOC-1 and BLOC-2. Our results suggest that SLC24A5 is a previously unreported nonsyndromic OCA candidate gene and that the SLC24A5 transporter is transported into mature melanosomes by HPS protein complexes.