Synergism between fibronectin and transforming growth factor-β1 in the production of substance P in monocytes of patients with myelofibrosis

Substance P (SP), also considered a proinflammatory cytokine, as well as others such as transforming growth factor-beta 1 (TGF-beta 1) and interleukin-1 (IL-1), and the extracellular matrix protein fibronectin (FN) have been associated with the pathophysiology of myelofibrosis. SP is encoded by the TAC1 gene. The relationships among SP, TGF-beta 1, IL-1 and FN are poorly understood. This study determined the mechanisms for concomitant production of IL-1, TGF-beta 1 and SP and also determined the synergistic role of FN in SP release. Enzyme-linked immunosorbent assay (ELISA) indicated increased levels of SP and TGF-beta 1 in the blood of patients with myelofibrosis. Monocytes, shown to be activated in patients with bone marrow (BM) fibrosis, expressed the TAC1 gene for SP release, in a nuclear factor-kappa B (NF kappa B)-dependent manner. Reporter gene assay with the 5' regulatory region of TAC1 indicated its expression by high levels of FN and TGF-beta 1. Immunohistochemical studies of paraffin-embedded BM biopsies from patients with myelofi brosis, and age-matched controls without fibrosis, indicated co-localization of SP and its receptor neurokinin-1 (NK1). In summary, myelofibrotic monocytes have autocrine loops that stimulate the release of SP and TGF-beta 1, and that are potentiated by fibronectin. The FN-mediated induction of SP in turn stimulates monocytes through autostimulation by NK1 receptors. These findings, combined with those of previous studies, demonstrate an adhesion-mediated NF kappa B/IL-1/TGF-beta 1 axis that can be initiated by increased FN in patients with myelofi brosis for the production of SP. These findings show how TGF-beta 1 and SP production are coupled, and suggest new therapeutic targets to reverse immune-mediated fibrosis.