Biomedical Engineering Reference
In-Depth Information
elegant approach has been to change this cytokine (or any other cytokine) into a
latent form that will be activated at the site of inflammation. To achieve this, the
latency associated protein (LAP) domain of TGF-
β
1 was fused to the IFN-
β
protein
to prevent IFN-
β
from binding to its receptor. Between the LAP-domain and the
IFN-
domain, a matrix-metalloprotease (MMP) cleavage site was introduced.
Because MMPs are locally produced at sites where tissue damage or remodeling is
taking place — for instance, at the site of inflammation or tumor expansion — IFN-
β
β
will be cleaved from the LAP domain and become active locally. LAP-MMP-IFN-
β
fusion-protein was shown to be cleaved by cerebrospinal or synovial fluid of
patients with inflammatory diseases. Additionally, the latent protein was shown to
be more efficient in a mouse model of arthritis than unmodified IFN-
β
[141].
As a converging point for multiple proinflammatory NF-
κ
B stimuli [142], IKK
β
is an ideal target for small-molecule kinase-inhibitors. Examples of IKK
inhibitors
under study are SPC-839, SC-514, PS-1145, and BMS-345541 (reviewed extensively
in [143]). SPC839 (a quinazoline analogue) and SC-514 (an aminothiophenecarbox-
amide derivative) are reversible ATP-binding site-targeting ATP-competitors, with
specificity for the ATP-binding site of IKK
β
β
over that of IKK
α
and other kinases.
To date, most IKK-inhibitors display a higher affinity for IKK
. The
realization that the alternative pathway may be hyperactivated in diseases in which
lymphocytes go awry and the fact that this pathway depends on IKK
β
than for IKK
α
α
and not on
inhibitors.
Inhibitors of kinases upstream of the IKK complex (kinases that activate IKK
IKK
β
or NEMO, will undoubtedly spur the search for more specific IKK
α
α
or
IKK
) could also be applied; however, great care will have to be taken regarding
the side effects of these compounds when these kinases are not specific for the
IKKs/NF-
β
B pathway
has been identified recently that is activated upon induction of DNA damage and is
κ
B pathway. Finally, it has to be remarked that a third NF-
κ
IKK-independent (
Chapter 4
) [144]. A variety of kinases have been found to play a
role in this pathway [145-148]. Each of these kinases may represent a new target
for small molecule inhibitors specifically inhibiting one of the three NF-
B pathways.
Another recent advance is the design of small peptides that interfere with
protein-protein interactions that are important for NF-
κ
B signaling. A short hexapep-
tide sequence (Leu-Asp-Trp-Ser-Trp-Leu) analogous to the NEMO-binding domain
(NBD) of IKK
κ
α
and IKK
β
disrupts the association of NEMO with both IKK-
α
and
B activation and inflammatory responses
[149
,
150]. The peptide has already proven its potential by sensitizing TRAIL resis-
tant cell lines to TRAIL, and by inhibiting mononuclear cell invasion and normal-
izing p65 expression in spinal cords of mice with experimental allergic encephalo-
myelitis (EAE, a model for multiple sclerosis) [151,152]. Interestingly, similar short
NBD-peptides have been altered by adding moieties that facilitate delivery into the
cell, such as HIV-TAT sequences, the homeodomain of antennapedia protein (a
Drosophila
transcription factor) and a cationic peptide transduction domain (PTD).
A TAT-NBD fusion peptide has been shown to inhibit LPS-induced NF-
IKK-
β
and inhibits cytokine induced NF-
κ
B activation
in polymorphonuclear neutrophils (PMNs) [153] and to block osteoclastogenesis,
to inhibit bone erosion, and to ameliorate inflammation in the joints of mice with
arthritis [154,175]. Application of NBD fused to the antennapedia homeodomain
improves lung edema and lung volume and reduces inflammation in a an acute
κ
