Biomedical Engineering Reference
In-Depth Information
4.4.2 Activators of Endothelium-Driven Innate Immunity of Macrophages
The endothelium plays a critical role in promoting inflammation in cardiovascu-
lar diseases and other chronic inflammatory conditions; accordingly, many small-
molecule screens have sought to identify agents to prevent endothelial cell activation.
Conversely, an augmented immune response can be protective against microbial
pathogens and in cancer immunotherapy. Nevertheless, small-molecule screens to
identify agents that induce endothelial cell (EC) activation had not been reported
prior to our studies. The identification of a family of chemical probes that augment
innate immunity through EC activation would provide a framework for understanding
the gene networks involved in endothelial inflammation, as well as the development
of novel endothelium-driven immunotherapeutic agents [64].
Activation of the endothelium is linked intricately to innate immunity. For exam-
ple, ECs activated by IFN
were shown to trigger the production of macrophage
inflammatory protein 1 alpha (MIP1
) from primary human monocytes [97]. Using
the designed EC-monocyte coculture system, we screened our pilot library of 642
carbo- and heterocycles, featuring 55 distinctive scaffolds, for their ability to activate
human ECs, which, in turn, trigger monocyte activation. We identified seven dis-
tinct scaffolds (
89
,
90
,
94
to
96
,
100
, and
104
; Scheme 4.30) among 35 compounds
derived from the sequence of phosphine-catalyzed annulation, Tebbe methylenation,
Diels-Alder reaction, and sometimes hydrolysis (Scheme 4.27) for their capacity to
bestow upon the endothelium the ability to trigger MIP1
and MIP1
production
from previously quiescent monocytes [64].
The octahydro-1,6-naphthyridine framework was particularly interesting in that it
exhibited the highest hit rate (all 10 of the octahydro-1,6-naphthyridin-4-ones in our
pilot library were active), and because the synthesis of octahydro-1,6-naphthyridin-
4-one analogs could be performed from resin-bound allenoates on a solid support.
For further analysis of structure-activity relationships, we synthesized 100 (1
×
10) octahydro-1,6-naphthyridin-4-one analogs using the tagging and split-and-pool
combinatorial techniques; as building blocks, we used 2-methyl-2,3-butadienoic acid
and 10 different
N
-sulfonylimines (Scheme 4.29). In addition, we prepared several
other octahydro-1,6-naphthyridine analogs, with different functional groups, through
solution-phase syntheses (Scheme 4.34).
After completing the syntheses of the analogs in the solid phase and the solution
phase, we dissolved the products in DMSO and analyzed their degrees of EC activa-
tion. The focused library of 96 analogs produced compounds with distinct capacities
for EC activation, revealing some essential structural features for the biological activ-
ity of the octahydro-1,6-naphthyridin-4-ones. In particular, the aryl groups on the N1
and N6 arylsulfonly groups were indispensible; both N1 mesyl (Ms) and N6 mesyl
naphthyridinone compounds (
104c
and
d
, Scheme 4.35) lost their activity. Based on
the fact that the mesylated naphthyridinone at N1 was inactive, it was not surprising
that the derivative
129
featuring a pyridyl ring was also inactive. On the other hand,
removal of the aryl group at C7 (analog
125
) did not affect the naphthyridinone's
ability to induce EC activation. At the same time, the alcohol
126
and its ethyl
ether
127
were active, confirming that the ketone group was less essential for the
naphthyridinone's EC-activating effect.
×
10
