CXCL12+ dermal fibroblasts promote neutrophil recruitment and host defense by recognition of IL-17.

The skin provides an essential barrier for host defense through rapid action of multiple resident and recruited cell types, but the complex communication network governing these processes is incompletely understood. To define these cell-cell interactions more clearly, we performed an unbiased network analysis of mouse skin during invasive S. aureus infection and revealed a dominant role for CXCL12+ fibroblast subsets in neutrophil communication. These subsets predominantly reside in the reticular dermis, express adipocyte lineage markers, detect IL-17 and TNFα, and promote robust neutrophil recruitment through NFKBIZ-dependent release of CXCR2 ligands and CXCL12. Targeted deletion of Il17ra in mouse fibroblasts resulted in greatly reduced neutrophil recruitment and increased infection by S. aureus. Analogous human CXCL12+ fibroblast subsets abundantly express neutrophil chemotactic factors in psoriatic skin that are subsequently decreased upon therapeutic targeting of IL-17. These findings show that CXCL12+ dermal immune acting fibroblast subsets play a critical role in cutaneous neutrophil recruitment and host defense.

Increased LL37 in psoriasis and other inflammatory disorders promotes LDL uptake and atherosclerosis.

Patients with chronic inflammatory disorders such as psoriasis have an increased risk of cardiovascular disease and elevated levels of LL37, a cathelicidin host defense peptide that has both antimicrobial and proinflammatory properties. To explore whether LL37 could contribute to the risk of heart disease, we examined its effects on lipoprotein metabolism and show that LL37 enhanced LDL uptake in macrophages through the LDL receptor (LDLR), scavenger receptor class B member 1 (SR-B1), and CD36. This interaction led to increased cytosolic cholesterol in macrophages and changes in expression of lipid metabolism genes consistent with increased cholesterol uptake. Structure-function analysis and synchrotron small-angle x-ray scattering showed structural determinants of the LL37-LDL complex that underlie its ability to bind its receptors and promote uptake. This function of LDL uptake is unique to cathelicidins from humans and some primates and was not observed with cathelicidins from mice or rabbits. Notably, Apoe-/- mice expressing LL37 developed larger atheroma plaques than did control mice, and a positive correlation between plasma LL37 and oxidized phospholipid on apolipoprotein B (OxPL-apoB) levels was observed in individuals with cardiovascular disease. These findings provide evidence that LDL uptake can be increased via interaction with LL37 and may explain the increased risk of cardiovascular disease associated with chronic inflammatory disorders.

Pyroglutamate-Aß 3 and 11 colocalize in amyloid plaques in Alzheimer's disease cerebral cortex with pyroglutamate-Aß 11 forming the central core.

N-terminal truncated amyloid beta (Aß) derivatives, especially the forms having pyroglutamate at the 3 position (AßpE3) or at the 11 position (AßpE11) have become the topic of considerable study. AßpE3 is known to make up a substantial portion of the Aß species in senile plaques while AßpE11 has received less attention. We have generated very specific polyclonal antibodies against both species. Each antibody recognizes only the antigen against which it was generated on Western blots and neither recognizes full length Aß. Both anti-AßpE3 and anti-AßpE11 stain senile plaques specifically in Alzheimer's disease cerebral cortex and colocalize with Aß, as shown by confocal microscopy. In a majority of plaques examined, AßpE11 was observed to be the dominant form in the innermost core. These data suggest that AßpE11 may serve as a generating site for senile plaque formation.

Limiting angiotensin II signaling with a cell-penetrating peptide mimicking the second intracellular loop of the angiotensin II type-I receptor.

A cell-penetrating peptide consisting of the second intracellular loop (IC2) of the angiotensin II (AngII) type-I receptor (AT1) linked to the HIV-transactivating regulatory protein (TAT) domain was used to identify the role of this motif In intracellular signal transduction. HEK-293 cells stably transfected with AT1R cDNA and primary cultures of human pulmonary artery smooth muscle cells expressing endogenous AT1 receptor were exposed to the cell-penetrating peptide construct, and the effect on angiotensin II signaling was determined. The AT1 IC2 peptide effectively inhibited AngII-stimulated phosphatidylinositol turnover and calcium influx. It also limited the activation of Akt/PKB as determined by an inhibition of phosphorylation of Akt at Ser473, and completely abolished the AngII-dependent activation of the transcriptional factor NFkappaB. In contrast, the AT1 IC2 peptide had no effect on AngII/AT1 receptor activation of ERK. These results illustrate the potential of using cell-penetrating peptides to both delineate receptor-mediated signal transduction and to selectively regulate G protein-coupled receptor signaling.