TWEAK/Fn14 Signals Mediate Burn Wound Repair.

TWEAK acts by engaging with Fn14 to regulate inflammatory responses, fibrosis, and tissue remodeling, which are central in the repair processes of wounds. This study aims to explore the potential role of the TWEAK/Fn14 pathway in the healing of cutaneous burn wounds. Third-degree burns were introduced in wild-type and Fn14-deficient BALB/c mice, followed by evaluation of wound areas and histological changes. The downstream cytokines including growth factors were also examined in lesional skin. Moreover, human dermal microvascular endothelial cells and dermal fibroblasts were analyzed in vitro upon TWEAK stimulation. The healing of burn wounds was delayed in Fn14-deficient mice and was accompanied by the suppression of inflammatory responses, growth factor production, and extracellular matrix synthesis. Moreover, TWEAK/Fn14 activation enhanced the migration and cytokine production of both dermal microvascular endothelial cells and dermal fibroblasts. TWEAK also facilitates the expression of α-SMA and palladin in dermal fibroblasts. Furthermore, transfection of Fn14 small interfering RNA abrogated such promotion effect of TWEAK on these cells. In conclusion, TWEAK/Fn14 signals mediate the healing of burn wounds, possibly involving TWEAK regulation of the function of resident cells.

TWEAK/Fn14 Interaction Confers Aggressive Properties to Cutaneous Squamous Cell Carcinoma.

Recent studies showed that TWEAK/Fn14 signaling participates in the progression of internal malignancies. However, its role in the biological properties of cutaneous squamous cell carcinoma (SCC) remains unclear. This study was designed to explore the effect of TWEAK/Fn14 activation on cutaneous SCC as well as the relevant mechanism. The expression of TWEAK and Fn14 was determined in tissue samples of patients with cutaneous SCC. Human primary keratinocytes and SCC cell lines were cultured in vitro, receiving stimulation of TWEAK. The xenografts of SCC were generated subcutaneously in BALB/c nude mice. The results showed that both TWEAK and Fn14 were highly expressed in human cutaneous SCC. Moreover, TWEAK/Fn14 activation promoted the proliferation, migration, and invasion of cultured SCC cells. Interestingly, TNFR2 was upregulated in cultured SCC cells, and the transfection of TNFR2 small interfering RNA abrogated the effect of TWEAK on these cells. Finally, the favorable effect of TWEAK/Fn14 signals was confirmed in BALB/c nude mice with SCC xenografts. In conclusion, TWEAK/Fn14 signals contribute to the progression of cutaneous SCC, possibly involving the TNF-α-independent TNFR2 signal transduction.

Visual Experience-Dependent Expression of Fn14 Is Required for Retinogeniculate Refinement.

Sensory experience influences the establishment of neural connectivity through molecular mechanisms that remain unclear. Here, we employ single-nucleus RNA sequencing to investigate the contribution of sensory-driven gene expression to synaptic refinement in the dorsal lateral geniculate nucleus of the thalamus, a region of the brain that processes visual information. We find that visual experience induces the expression of the cytokine receptor Fn14 in excitatory thalamocortical neurons. By combining electrophysiological and structural techniques, we show that Fn14 is dispensable for early phases of refinement mediated by spontaneous activity but that Fn14 is essential for refinement during a later, experience-dependent period of development. Refinement deficits in mice lacking Fn14 are associated with functionally weaker and structurally smaller retinogeniculate inputs, indicating that Fn14 mediates both functional and anatomical rearrangements in response to sensory experience. These findings identify Fn14 as a molecular link between sensory-driven gene expression and vision-sensitive refinement in the brain.

Src Promotes Metastasis of Human Non-Small Cell Lung Cancer Cells through Fn14-Mediated NF-κB Signaling.

BACKGROUND Src and Fn14 are implicated in the aggressiveness of non-small cell lung cancer (NSCLC) cells, yet the molecular mechanism is not fully understood. MATERIAL AND METHODS The proliferation, migration, and invasion of HCC827 cells with Src knockdown were examined in vitro. The expression of Fn14 and the activation of NF-κB signaling pathway in Src-silenced HCC827 cells were detected by western blot. The role of Fn14 in Src-regulated cell migration/invasion and activation of NF-κB signaling was investigated by overexpressing Fn14 in Src knockdown NSCLC cells. Furthermore, the pro-metastatic role of Src was validated in a NSCLC metastasis mouse model. RESULTS Knockdown of Src inhibited the proliferation, migration, and invasion of HCC827 cells, which was associated with reduced levels of Fn14, p-IκBα, p-IKKß, and nuclear NF-κB p65. Overexpression of Fn14 restored the potential of migration and invasion as well as the activation of NF-κB signaling in Src-silenced NSCLC cells. In addition, silencing of Src suppressed lung metastasis of HCC827 cells in mice, and inhibited the expression of Fn14 and nuclear translocation of NF-κB p65 in vivo. CONCLUSIONS The data demonstrated that the Src/Fn14/NF-κB axis plays a critical role in NSCLC metastasis.

TWEAK and RIPK1 mediate a second wave of cell death during AKI.

Acute kidney injury (AKI) is characterized by necrotic tubular cell death and inflammation. The TWEAK/Fn14 axis is a mediator of renal injury. Diverse pathways of regulated necrosis have recently been reported to contribute to AKI, but there are ongoing discussions on the timing or molecular regulators involved. We have now explored the cell death pathways induced by TWEAK/Fn14 activation and their relevance during AKI. In cultured tubular cells, the inflammatory cytokine TWEAK induces apoptosis in a proinflammatory environment. The default inhibitor of necroptosis [necrostatin-1 (Nec-1)] was protective, while caspase inhibition switched cell death to necroptosis. Additionally, folic acid-induced AKI in mice resulted in increased expression of Fn14 and necroptosis mediators, such as receptor-interacting protein kinase 1 (RIPK1), RIPK3, and mixed lineage domain-like protein (MLKL). Targeting necroptosis with Nec-1 or by genetic RIPK3 deficiency and genetic Fn14 ablation failed to be protective at early time points (48 h). However, a persistently high cell death rate and kidney dysfunction (72-96 h) were dependent on an intact TWEAK/Fn14 axis driving necroptosis. This was prevented by Nec-1, or MLKL, or RIPK3 deficiency and by Nec-1 stable (Nec-1s) administered before or after induction of AKI. These data suggest that initial kidney damage and cell death are amplified through recruitment of inflammation-dependent necroptosis, opening a therapeutic window to treat AKI once it is established. This may be relevant for clinical AKI, since using current diagnostic criteria, severe injury had already led to loss of renal function at diagnosis.

TWEAK-Fn14 Influences Neurogenesis Status via Modulating NF-κB in Mice with Spinal Cord Injury.

The aim of our research is to investigate the regulatory role of TNF-like weak inducer of apoptosis- fibroblast growth factor-inducible 14 (TWEAK-Fn14) pathway in nuclear factor-kappa B (NF-κB) expression and neurogenesis status after spinal cord injury (SCI). We constructed a mice model of spinal cord injury and injected different lentiviral vectors which were transfected with TWEAK, TWEAK small interfering RNA (siRNA) and Fn14 siRNA into different groups of mice. Locomotor functional recovery status of the hind limb in mice was assessed using the Basso, Beattie and Bresnahan (BBB) test. Apoptosis status in the injured area was examined via TDT-mediated dUTP-biotin nick end-labeling (TUNEL) staining, the expression of GAP-43 in injured spinal cord was quantified by immunohistochemistry and expressions of TWEAK, Fn14, NF-κB, TNF-α, and IL-1ß were evaluated by either western blot or ELISA. The expressions of TWEAK, Fn14, and NF-κB in the model group were significantly higher compared with those in the control group. Furthermore, the TWEAK group in which TWEAK was overexpressed exhibited significantly higher expressions of TWEAK, Fn14, and NF-κB, TNF-α and IL-1ß in relation to those in the model group (P < 0.05 for all). Moreover, the transfection of Fn14 siRNA antagonized the above effect of TWEAK transfection on injured mice. On the other hand, the TWEAK siRNA group in which the expression of TWEAK was inhibited exhibited significantly lower expressions of TWEAK, Fn14, NF-κB, TNF-α, and IL-1ß (P < 0.05 for all). Moreover, the transfection of TWEAK siRNA enhanced the locomotor functional recovery status in injured mice and suppressed the apoptosis of injured areas (P < 0.05 for all). In conclusion, stimulating the TWEAK-Fn14 pathway may elevate the expression of NF-κB, thereby slow the function recovery of SCI mice whereas inhibiting the TWEAK-Fn14 pathway may improve the neurogenesis status in mice with spinal cord injuries.