Sphingosine 1-phosphate and cell migration: resistance to angiogenesis inhibitors

Treatment of collagen-induced arthritis with recombinant plasminogen-related protein B: a novel inhibitor of angiogenesis

BACKGROUND

We have previously reported that recombinant human plasminogen-related protein B (rPRP-B), a putative 9-kDa protein that closely resembles the activation peptide of plasminogen, has shown significant inhibition of tumor growth through inhibition of angiogenesis. Based on recent reports suggesting a close relationship between rheumatoid arthritis (RA) and angiogenesis, we hypothesized that this compound would regulate inflammatory conditions in RA. The present study therefore tested the effects of rPRP-B in the treatment of collagen-induced arthritis (CIA) to elucidate the mechanisms underlying these effects.

METHODS

DBA/1J mice immunized with type II collagen to induce CIA were monitored to assess the effects of rPRP-B on clinical severity of the disease. Pathological changes in joints, including vessel formation and vascular endothelial growth factor (VEGF) production, were examined histologically. Bone destruction was radiologically evaluated. In vitro studies on the effects of rPRP-B on cell proliferation and production of VEGF in interleukin (IL)-1β or basic fibroblast growth factor (bFGF)-stimulated human synoviocytes were also performed.

RESULTS

Development of CIA was effectively inhibited by rPRP-B. Radiological examinations revealed that the protein reduced bone destruction in CIA. CIA-induced vessel formation and VEGF expression in vivo were also reduced. In vitro mechanistic studies demonstrated that rPRP-B affected human synoviocyte proliferation and VEGF production stimulated by IL-1β and bFGF.

CONCLUSIONS

Given the ability to effectively promote multistep anti-angiogenic activities, including cell growth inhibition and cytokine regulation, rPRP-B represents a promising candidate for a novel therapeutic agent against RA.

Dupuytren's fibroblast contractility by sphingosine-1-phosphate is mediated through non-muscle myosin II

PURPOSE

Previous studies suggest that Dupuytren's disease is caused by fibroblast and myofibroblast contractility within Dupuytren's nodules; however, the stimulus for cell contractility is unknown. Sphingosine-1-phosphate (S1P) is a serum-derived lysophospholipid mediator that enhances cell contractility by activating the S1P receptor, S1P(2). It is hypothesized that S1P stimulates Dupuytren's fibroblast contractility through S1P(2) activation of non-muscle myosin II (NMMII). This investigation examined the role of S1P and NMMII activation in Dupuytren's disease progression and suggests potential targets for treatment.

METHODS

We enmeshed Dupuytren's fibroblasts into fibroblast-populated collagen lattices (FPCLs) and assayed S1P-stimulated FPCL contraction in the presence of the S1P(2) receptor inhibitor JTE-013, the Rho kinase inhibitor Y-27632, the myosin light chain kinase inhibitor ML-7, and the NMMII inhibitor blebbistatin. Tissues from Dupuytren's fascia (n = 10) and normal palmar fascia (n = 10) were immunostained for NMMIIA and NMMIIB.

RESULTS

Sphingosine-1-phosphate stimulated FPCL contraction in a dose-dependent manner. Inhibition of S1P(2) and NMMII prevented S1P-stimulated FPCL contraction. Rho kinase and myosin light chain kinase inhibited both S1P and control FPCL contraction. Dupuytren's nodule fibroblasts robustly expressed NMMIIA and NMMIIB, compared with quiescent-appearing cords and normal palmar fascia.

CONCLUSIONS

Sphingosine-1-phosphate promotes Dupuytren's fibroblast contractility through S1P(2), which stimulates activation of NMMII. NMMII isoforms are ubiquitously expressed throughout Dupuytren's nodules, which suggests that nodule fibroblasts are primed to respond to S1P stimulation to cause contracture formation. S1P-promoted activation of NMMII may be a target for disease treatment.

Role of biologically active sphingolipids in tumor growth

This review highlights the literature on the effects of biologically active sphingolipids (sphingosine, ceramide, sphingomyelin, glucosylceramide, gangliosides GM1, GM2, GM3, GD3, etc.) on proliferation, apoptosis, metastases, and invasiveness of tumor cells and the putative role of sphingolipids in chemotherapy of malignant tumors.

Overexpression of sphingosine-1-phosphate lyase or inhibition of sphingosine kinase in Dictyostelium discoideum results in a selective increase in sensitivity to platinum-based chemotherapy drugs

The efficacy of the chemotherapy drug cisplatin is often limited due to resistance of the tumors to the drug, and increasing the potency of cisplatin without increasing its concentration could prove beneficial. A previously characterized Dictyostelium discoideum mutant with increased resistance to cisplatin was defective in the gene encoding sphingosine-1-phosphate (S-1-P) lyase, which catalyzes the breakdown of S-1-P, an important regulatory molecule in cell function and development and in the regulation of cell fate. We hypothesized that the increased resistance to cisplatin was due to an elevation of S-1-P and predicted that lowering levels of S-1-P should increase sensitivity to the drug. We generated three strains that stably overexpress different levels of the S-1-P lyase. The overexpressor strains have reduced growth rate and, confirming the hypothesis, showed an expression-dependent increase in sensitivity to cisplatin. Consistently, treating the cells with D-erythro-N,N,-dimethylsphingosine, a known inhibitor of sphingosine kinase, increased the sensitivity of mutant and parent cells to cisplatin, while addition of exogenous S-1-P or 8-Br-cyclic AMP made the cells more resistant to cisplatin. The increased sensitivity of the overexpressors to cisplatin was also observed with the cisplatin analog carboplatin. In contrast, the response to doxorubicin, 5-flurouracil, or etoposide was unaffected, indicating that the involvement of the sphingolipid metabolic pathway in modulating the response to cisplatin is not part of a global genotoxic stress response. The augmented sensitivity to cisplatin appears to be the result of an intracellular signaling function of S-1-P, because D. discoideum does not appear to have endothelial differentiation growth (EDG/S1P) receptors. Overall, the results show that modulation of the sphingolipid pathway at multiple points can result in increased sensitivity to cisplatin and has the potential for increasing the clinical usefulness of this important drug.