TRAIL-Dependent Resolution of Pulmonary Fibrosis

Extracellular PKM2 facilitates organ-tissue fibrosis progression

Persistent activation of fibroblasts and resistance of myofibroblasts to turnover play important roles in organ-tissue fibrosis development and progression. The mechanism that mediates apoptosis resistance of myofibroblasts is not understood. Here, we report that myofibroblasts express and secrete PKM2. Extracellular PKM2 (EcPKM2) facilitates progression of fibrosis by protecting myofibroblasts from apoptosis. EcPKM2 upregulates arginase-1 expression in myofibroblasts and therefore facilitates proline biosynthesis and subsequent collagen production. EcPKM2 interacts with integrin αvβ3 on myofibroblasts to activate FAK-PI3K signaling axis. Activation of FAK-PI3K by EcPKM2 activates downstream NF-κB survival pathway to prevent myofibroblasts from apoptosis. On the other hand, activation of FAK- PI3K by EcPKM2 suppresses PTEN to subsequently upregulate arginase-1 in myofibroblasts. Our studies uncover an important mechanism for organ fibrosis progression. More importantly, an antibody disrupting the interaction between PKM2 and integrin αvβ3 is effective in reversing fibrosis, suggesting a possible therapeutic strategy and target for treatment of organ fibrosis.

Quercetin Enhances Ligand-induced Apoptosis in Senescent Idiopathic Pulmonary Fibrosis Fibroblasts and Reduces Lung Fibrosis In Vivo

Although cellular senescence may be a protective mechanism in modulating proliferative capacity, fibroblast senescence is now recognized as a key pathogenic mechanism in idiopathic pulmonary fibrosis (IPF). In aged mice, abundance and persistence of apoptosis-resistant senescent fibroblasts play a central role in nonresolving lung fibrosis after bleomycin challenge. Therefore, we investigated whether quercetin can restore the susceptibility of senescent IPF fibroblasts to proapoptotic stimuli and mitigate bleomycin-induced pulmonary fibrosis in aged mice. Unlike senescent normal lung fibroblasts, IPF lung fibroblasts from patients with stable and rapidly progressing disease were highly resistant to Fas ligand (FasL)-induced and TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. Senescent IPF fibroblasts exhibited decreased expression of FasL and TRAIL receptors and caveolin-1, as well as increased AKT activation, compared with senescent normal lung fibroblasts. Although quercetin alone was not proapoptotic, it abolished the resistance to FasL- or TRAIL-induced apoptosis in IPF fibroblasts. Mechanistically, quercetin upregulated FasL receptor and caveolin-1 expression and modulated AKT activation. In vivo quercetin reversed bleomycin-induced pulmonary fibrosis and attenuated lethality, weight loss, and the expression of pulmonary senescence markers p21 and p19-ARF and senescence-associated secretory phenotype in aged mice. Collectively, these data indicate that quercetin reverses the resistance to death ligand-induced apoptosis by promoting FasL receptor and caveolin-1 expression and inhibiting AKT activation, thus mitigating the progression of established pulmonary fibrosis in aged mice. Therefore, quercetin may be a viable therapeutic option for IPF and other age-related diseases that progress with the accumulation of senescent fibroblasts.

Dually Efficacious Medicine Against Fibrosis and Cancer

Although there is a contemporary consensus of managing a severe disease with multi-targeted approach-based therapeutic combinations, it should not be ignored that certain patho-biological pathways are shared by distinct medical conditions and can be exploited to develop an exceptional type of medication conferring a dual efficacy. This article thus presents a spectrum of emerging molecular targets that substantially contribute to the pathogenesis of both fibrotic and neoplastic disorders, including kinase activities, cytokine cascades, and protein dynamics among others. Moreover, recently approved therapeutic agents in this regard have been sorted out to corroborate the drug’s ability upon targeting each one of these molecular pathways to treat fibrosis and cancer simultaneously. It not only streamlines an overlapping mechanistic profile in the pathogenesis across these two medical conditions, but also inspires clinicians and pharmaceutical innovation to tackle concomitant diseases, such as fibrosis and cancer, with an optimally efficacious medication.