Investigation of JAKs/STAT-3 in lipopolysaccharide-induced intestinal epithelial cells

Abstract

Janus-activated kinase (JAKs)-signal transducer and activator of transcription 3 (STAT-3) signalling play critical roles in immunoregulation and immunopathology, which involve inflammatory responses and enteritis. JAK phosphorylates STAT-3 in response to stimulation by cytokines or growth factors, and then activates or represses the gene expression. STAT-3 is activated persistently in cancer cells and contributes to the malignant progression of various types of cancer and inflammation. To elucidate the different roles of JAKs in the activation of STAT-3, the lipopolysaccharide-induced primary intestinal epithelial cell (IEC) acute inflammatory model was established. Small interference RNAs (siRNAs) were then employed to attenuate the expression levels of JAKs. Real-time quantitative reverse transcription-polymerase chain reaction (PCR) (qRT-PCR) revealed that JAK mRNA levels were reduced efficiently by JAK-specific siRNAs. Under the IEC inflammatory model transfected with si-JAK, which equates to effective silencing, qRT-PCR and Western blot assays, suggested that knockdowns of JAK attenuated the JAK-induced down-regulation of STAT-3 at the mRNA or protein levels. In particular, JAK1 played a key role, which was consistent with the RNA-Seq results. Subsequently, the expression levels of proinflammatory cytokines interleukin (IL)-1β and tumour necrosis factor (TNF)-α were down-regulated in the IEC inflammatory model transfected with si-JAK1. JAK1 appears as a direct activator for STAT-3, whereas treatments targeting JAK1 repressed STAT-3 sufficiently pathways in the IEC inflammatory model. Therefore, the control of JAK1 using siRNAs has the potential to be an effective strategy against enteritis.

Alkaloids from Aconitum carmichaelii Alleviates DSS-Induced Ulcerative Colitis in Mice via MAPK/NF-κB/STAT3 Signaling Inhibition

“…The JAK/STATs signaling pathway is a series of multi-effect cascade signal transduction pathways stimulated by cytokines, which mediates the occurrence and development of UC [ 38 ]. JAK2 and STAT3 are key regulators in the JAK/STAT signaling pathway [ 39 ], wherein JAK2 phosphorylates downstream STAT3 after recognizing extracellular signals; then, p-STAT3 regulates the expression of multiple downstream genes and participate in the regulation of apoptosis and inflammation [ 39 , 40 ]. Presently, AAC significantly downregulated the protein expressions of STAT3 ( Figure 5(g) ) and JAK2 ( Figure 5(i) ) in the colon tissue of ACC-L/M/H groups.…”