ABSTRACT
Normal hair growth occurs in cycles, comprising growth (anagen), cessation (catagen) and rest (telogen). Upon aging, the initiation of anagen is significantly delayed, which results in impaired hair regeneration. Hair regeneration is driven by hair follicle stem cells (HFSCs). We show here that aged HFSCs present with a decrease in canonical Wnt signaling and a shift towards non-canonical Wnt5a driven signaling which antagonizes canonical Wnt signaling. Elevated expression of Wnt5a in HFSCs upon aging results in elevated activity of the small RhoGTPase Cdc42 as well as a change in the spatial distribution of Cdc42 within HFSCs. Treatment of aged HFSC with a specific pharmacological inhibitor of Cdc42 activity termed CASIN to suppress the aging-associated elevated activity of Cdc42 restored canonical Wnt signaling in aged HFSCs. Treatment of aged mice in vivo with CASIN induced anagen onset and increased the percentage of anagen skin areas. Aging-associated functional deficits of HFSCs are at least in part intrinsic to HFSCs and can be restored by rational pharmacological approaches.
Subject(s)
Hair Follicle/growth & development , Rejuvenation/physiology , Stem Cells/metabolism , Wnt Signaling Pathway , Wnt-5a Protein/genetics , Animals , Cellular Senescence/physiology , MiceABSTRACT
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
ABSTRACT
In monocytic cells, Toll-like receptor 4 (TLR4)- and TLR2-induced reactive oxygen species (ROS) cause oxidative stress and inflammatory response; however, the mechanism is not well understood. The present study investigated the role of interleukin-1 receptor-associated kinase (IRAK), extracellular signal-regulated kinase (ERK), p67phox and Nox-2 in TLR4- and TLR2-induced ROS generation during interleukin-1 beta (IL-1ß) transcription, processing, and secretion. An IRAK1/4 inhibitor, U0126, PD98059, an NADPH oxidase inhibitor (diphenyleneiodonium (DPI)), and a free radical scavenger (N-acetyl cysteine (NAC))-attenuated TLR4 (lipopolysaccharide (LPS))- and TLR2 (Pam3csk4)-induced ROS generation and IL-1ß production in THP-1 and primary human monocytes. An IRAK1/4 inhibitor and siRNA-attenuated LPS- and Pam3csk4-induced ERK-IRAK1 association and ERK phosphorylation and activity. LPS and Pam3csk4 also induced IRAK1/4-, ERK- and ROS-dependent activation of activator protein-1 (AP-1), IL-1ß transcription, and IL-1ß processing because significant inhibition in AP-1 activity, IL-1ß transcription, Pro- and mature IL-ß expression, and caspase-1 activity was observed with PD98059, U0126, DPI, NAC, an IRAK1/4 inhibitor, tanshinone IIa, and IRAK1 siRNA treatment. IRAK-dependent ERK-p67phox interaction, p67phox translocation, and p67phox-Nox-2 interaction were observed. Nox-2 siRNA significantly reduced secreted IL-1ß, IL-1ß transcript, pro- and mature IL-1ß expression, and caspase-1 activity indicating a role for Nox-2 in LPS- and Pam3csk4-induced IL-1ß production, transcription, and processing. In the present study, we demonstrate that the TLR4- and TLR2-induced IRAK-ERK pathway cross-talks with p67phox-Nox-2 for ROS generation, thus regulating IL-1ß transcription and processing in monocytic cells.
Subject(s)
Extracellular Signal-Regulated MAP Kinases/metabolism , Interleukin-1 Receptor-Associated Kinases/metabolism , Interleukin-1beta/genetics , Membrane Glycoproteins/metabolism , Monocytes/metabolism , NADPH Oxidases/metabolism , Phosphoproteins/metabolism , Toll-Like Receptor 2/metabolism , Toll-Like Receptor 4/metabolism , Transcription, Genetic , Cell Line , Humans , Interleukin-1beta/metabolism , Lipopeptides/pharmacology , Lipopolysaccharides/pharmacology , Monocytes/drug effects , NADPH Oxidase 2 , Reactive Oxygen Species/metabolism , Signal Transduction/drug effects , Transcription Factor AP-1/metabolism , Transcription, Genetic/drug effectsABSTRACT
The recent failure of candidate drugs like cholesterol ester transfer protein (CETP) and acyl-CoA:cholesterol acyltransferase (ACAT) inhibitors calls for a revised approach for screening anti-atherosclerotic drugs and development of new models of atherosclerosis. For this it is important to understand the mechanism of the disease in a particular model. Models simultaneously showing hyperlipidemia, inflammation and associated complications of diabetes and hypertension will serve the purpose better as they mimic the actual clinical condition. Besides this, analyzing candidate molecules in vivo, in vitro and at various levels of atherosclerosis progression is important. Models based on various cells and process involved in atherosclerosis should be used for screening candidate molecules. The challenge lies in bridging the gap between genetically friendly small animal and human-like bigger animal models. Sequencing of the mouse and human genome, development of a single nucleotide polymorphism (SNP) database and in silico quantitative trait loci (QTL) linkage analysis may enhance the understanding of atherosclerosis and help develop new therapeutic targets.
