Effect of Anti-S100A4 Monoclonal Antibody Treatment on Experimental Skin Fibrosis and Systemic Sclerosis-Specific Transcriptional Signatures in Human Skin.

OBJECTIVE: S100A4 is a DAMP protein. S100A4 is overexpressed in patients with systemic sclerosis (SSc), and levels correlate with organ involvement and disease activity. S100A4-/- mice are protected from fibrosis. The aim of this study was to assess the antifibrotic effects of anti-S100A4 monoclonal antibody (mAb) in murine models of SSc and in precision cut skin slices of patients with SSc. METHODS: The effects of anti-S100A4 mAbs were evaluated in a bleomycin-induced skin fibrosis model and in Tsk-1 mice with a therapeutic dosing regimen. In addition, the effects of anti-S100A4 mAbs on precision cut SSc skin slices were analyzed by RNA sequencing. RESULTS: Inhibition of S100A4 was effective in the treatment of pre-established bleomycin-induced skin fibrosis and in regression of pre-established fibrosis with reduced dermal thickening, myofibroblast counts, and collagen accumulation. Transcriptional profiling demonstrated targeting of multiple profibrotic and proinflammatory processes relevant to the pathogenesis of SSc on targeted S100A4 inhibition in a bleomycin-induced skin fibrosis model. Moreover, targeted S100A4 inhibition also modulated inflammation- and fibrosis-relevant gene sets in precision cut SSc skin slices in an ex vivo trial approach. Selected downstream targets of S100A4, such as AMP-activated protein kinase, calsequestrin-1, and phosphorylated STAT3, were validated on the protein level, and STAT3 inhibition was shown to prevent the profibrotic effects of S100A4 on fibroblasts in human skin. CONCLUSION: Inhibition of S100A4 confers dual targeting of inflammatory and fibrotic pathways in complementary mouse models of fibrosis and in SSc skin. These effects support the further development of anti-S100A4 mAbs as disease-modifying targeted therapies for SSc.

Non-classical regulation of ß1- and ß 2-adrenoceptor-mediated inotropic responses in rat heart ventricle by the G protein Gi.

Studies suggest that increased activity of Gi contributes to the reduced ß-adrenoceptor-mediated inotropic response (ßAR-IR) in failing cardiomyocytes and that ß2AR-IR but not ß1AR-IR is blunted by dual coupling to Gs and Gi. We aimed to clarify the role of Gi upon the ß1AR-IR and ß2AR-IR in Sham and failing myocardium by directly measuring contractile force and cAMP accumulation. Contractility was measured ex vivo in left ventricular strips and cAMP accumulation in cardiomyocytes from rats with post-infarction heart failure (HF) or sham operates (Sham). The ß2AR-IR in Sham and HF was small and was amplified by simultaneously inhibiting phosphodiesterases 3 and 4 (PDE3&4). In HF, the inotropic response and cAMP accumulation evoked by ß1AR- or ß2AR-stimulation were reduced. Inactivation of Gi with pertussis toxin (PTX) did not restore the ß1AR-IR or ß2AR-IR in HF to Sham levels but did enhance the maximal ß2AR-IR. PTX increased both ß1AR- and ß2AR-evoked cAMP accumulation more in Sham than that in HF, and HF levels approached those in untreated Sham. The potency of agonists at ß1 and at ß2ARs (only under PDE3&4 inhibition) was increased in HF and by PTX in both HF and Sham. Without PDE3&4 inhibition, PTX increased only the maximal ß2AR-IR, not potency. We conclude that Gi regulates both ß1AR- and ß2AR-IR independent of receptor coupling with Gi. Gi together with PDE3&4 tonically restrict the ß2AR-IR. Gi inhibition did not restore the ßAR-IR in HF despite increasing cAMP levels, suggesting that the mechanism of impairment resides downstream to cAMP signalling.