The laminin-binding integrins regulate nuclear factor kappa-β-dependent epithelial cell polarity and inflammation

The main laminin (LM)-binding integrins α3β1, α6β1 and α6β4 are co-expressed in the developing kidney collecting duct (CD) system. We previously showed that deleting the integrin α3 or α6 subunit in the ureteric bud (UB), which gives rise to the kidney collecting system, caused either a mild or no branching morphogenesis phenotype, respectively. To determine whether these two integrin subunits co-operate in kidney CD development, we deleted α3 and α6 in the developing UB. The collecting system of the double knockout phenocopied the α3 integrin conditional knockout. However, with age the mice developed severe inflammation and fibrosis around the CDs resulting in kidney failure. Integrin α3α6 null CD epithelial cells showed increased secretion of pro-inflammatory cytokines and displayed mesenchymal characterisitcs causing loss of barrier function. These features resulted from increased NF-κB activity, which regulated the Snail/Slug transcription factors and their downstream targets. These data suggest that LM-binding integrins play a key role in the maintenance of kidney tubule epithelial cell polarity and decrease pro-inflammatory cytokine secretion by regulating NF-κB-dependent signaling.

Blocking antibodies against integrin-α3, integrin-αM, and integrin-αMβ2 de-differentiate myofibroblasts and reverse lung and kidney fibroses in a mouse model

Fibrosis is involved in 45% of deaths in the United States, and no treatment exists to reverse the progression of the disease. Myofibroblasts are key to the progression and maintenance of fibrosis. We investigated features of cell adhesion necessary for monocytes to differentiate into myofibroblasts, seeking to identify pathways key to myofibroblast differentiation. Blocking antibodies against integrins α3, αM, and αMβ2 de-differentiate myofibroblasts in vitro, lower the pro-fibrotic secretome of myofibroblasts, and reverse fibrosis in vivo. Blocking key integrins may be an effective therapeutic for the treatment and reversal of fibrosis.

Paracoccidioides brasiliensis downmodulates α3 integrin levels in human lung epithelial cells in a TLR2-dependent manner

Paracoccidioidomycosis (PCM) is the most prevalent systemic mycosis in Latin America and may be caused by the species Paracoccidioides brasiliensis. In the lungs, this fungus interacts with epithelial cells, activating host cell signalling pathways, resulting in the production of inflammatory mediators. This event may be initiated through the activation of Pattern-Recognition Receptors such as Toll-like Receptors (TLRs). By interacting with cell wall components, TLR2 is frequently related to fungal infections. In this work, we show that, after 24 h post-infection with P. brasiliensis, A549 lung epithelial cells presented higher TLR2 levels, which is important for IL-8 secretion. Besides, integrins may also participate in pathogen recognition by host cells. We verified that P. brasiliensis increased α3 integrin levels in A549 cells after 5 h of infection and promoted interaction between this receptor and TLR2. However, after 24 h, surprisingly, we verified a decrease of α3 integrin levels, which was dependent on direct contact between fungi and epithelial cells. Likewise, we observed that TLR2 is important to downmodulate α3 integrin levels after 24 h of infection. Thus, P. brasiliensis can modulate the host inflammatory response by exploiting host cell receptors and cell signalling pathways.