Novel phenanthridinone inhibitors of poly (adenosine 5'-diphosphate-ribose) synthetase: potent cytoprotective and antishock agents.
OBJECTIVE
To synthesize novel inhibitors of the nuclear enzyme poly(adenosine 5'-diphosphate [ADP]-ribose) synthetase (PARS), also known as poly(ADP-ribose) polymerase (PARP), and to test them in in vitro models of oxidant-induced cytotoxicity and in endotoxin and splanchnic occlusion-reperfusion-induced shock.


METHODS
Randomized, prospective laboratory study.


METHODS
Research laboratory.


METHODS
Murine macrophages, thymocytes, and endothelial cells; Balb/c mice and Wistar rats.


METHODS
Macrophages and endothelial cells were treated with peroxynitrite and bleomycin to induce PARS activation, and thymocytes were treated with peroxynitrite to induce cell necrosis. Novel PARS inhibitors were synthesized and used to reduce PARS activation and to reverse cytotoxicity. Balb/c mice were subjected to splanchnic occlusion and reperfusion and were pretreated with various doses (1-10 mg/kg intraperitoneally) of PJ34, a selected, potent, water-soluble PARS inhibitor. The passage of fluorescein isothiocyanate-conjugated dextran (4 kDa) was analyzed in everted gut ileal sacs incubated ex vivo as an index of gut permeability. Wistar rats were subjected to Escherichia coli bacterial lipopolysaccharide (40 mg/kg intraperitoneally). PJ34 was also used at 10 mg/kg intraperitoneally, 1 hr before lipopolysaccharide or at 25 mg/kg intraperitoneally 1 hr after lipopolysaccharide treatment. Serum concentrations of indicators or multiple organ injury, concentrations of various proinflammatory mediators, and tissue concentrations of myeloperoxidase and malondialdehyde were measured. In addition, survival rates and vascular contractile and relaxant responses were recorded.


RESULTS
Appropriate modifications of the phenanthridinone core structure yielded significant increases in the potency of the compounds, both as PARS inhibitors and as cytoprotective agents. The compound N-(6-oxo-5,6-dihydro-phenanthridin-2-yl) -N,N-dimethylacetamide (designated as PJ34) was one of the potent PARS inhibitors of the series, and it dose-dependently protected against thymocyte necrosis, with a half-maximal restoration of cell viability of 35 nM and complete protection at 200 nM. PARS activation also was visualized by immunohistochemistry and was dose-dependently suppressed by PJ34. The effect of PJ34 was dose-dependently reversed by excess nicotinamide adenine dinucleotide (oxidized). The PARS inhibitors dose-dependently suppressed proinflammatory cytokine and chemokine production and restored viability in immunostimulated macrophages. PJ34 was selected for the subsequent in vivo studies. PJ34 significantly protected against splanchnic reperfusion-induced intestinal hyperpermeability in the mouse. PJ34 reduced peak plasma concentrations of tumor necrosis factor-alpha, interleukin-1beta, and nitrite/nitrate in the plasma of lipopolysaccharide-treated rats. PJ34 ameliorated the lipopolysaccharide-induced increases in indexes of liver and kidney failure and concentrations of myeloperoxidase and malondialdehyde in the lung and gut. Lipopolysaccharide elicited vascular dysfunction, which was normalized by PJ34. Lipopolysaccharide-induced mortality was reduced by PJ34 (both pre- and posttreatment).


CONCLUSIONS
The novel series of phenanthridinone PARS inhibitors have potent cytoprotective effects in vitro and significant protective effects in shock and reperfusion injury in rodent models in vivo.
Jagtap
Prakash
P
Inotek Corporation, Beverly, MA 01915, USA.
Soriano
Francisco Garcia
FG
Virág
László
L
Liaudet
Lucas
L
Mabley
Jon
J
Szabó
Eva
E
Haskó
György
G
Marton
Anita
A
Lorigados
Clara Batista
CB
Gallyas
Ferenc
F
Sümegi
Balázs
B
Hoyt
Dale G
DG
Baloglu
Erkan
E
VanDuzer
John
J
Salzman
Andrew L
AL
Southan
Garry J
GJ
Szabó
Csaba
C
D000818:Animals; D001761:Bleomycin / Q000494:pharmacology; D002478:Cells, Cultured; D019610:Cytoprotection; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007375:Interleukin-1 / Q000097:blood; D007668:Kidney / Q000737:chemistry; D008070:Lipopolysaccharides / Q000494:pharmacology; D008168:Lung / Q000737:chemistry; D008315:Malondialdehyde / Q000032:analysis; D051379:Mice; D008807:Mice, Inbred BALB C; D009566:Nitrates / Q000097:blood; D009573:Nitrites / Q000097:blood; D009195:Peroxidase / Q000032:analysis; D030421:Peroxynitrous Acid / Q000494:pharmacology; D010616:Phenanthrenes / Q000494:pharmacology*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D051381:Rats; D017208:Rats, Wistar; D012769:Shock / Q000517:prevention & control*; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis
D004791:Enzyme Inhibitors; D007375:Interleukin-1; D008070:Lipopolysaccharides; C434926:N-(oxo-5,6-dihydrophenanthridin-2-yl)-N,N-dimethylacetamide hydrochloride; D009566:Nitrates; D009573:Nitrites; D010616:Phenanthrenes; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D014409:Tumor Necrosis Factor-alpha; D001761:Bleomycin; D030421:Peroxynitrous Acid; D008315:Malondialdehyde; C040601:phenanthridone; D009195:Peroxidase