[26] On the other hand, TDP-43-immunoreactive structures were not detected in the vicinity of highly electron-dense BBs with central clear spaces containing Alectinib research buy filaments (Fig. 3c), corresponding

to an advanced stage of BB formation.[26] Murayama et al.[7] have reported that BB-related ubiquitin-positive structures are more frequently observed in ALS patients with shorter disease duration ranging from 10 to 38 months. Quantitative analysis also showed the highest numbers of ubiquitin-positive inclusions in cases with short duration.[27] By contrast, no significant correlation has been found between the number of BB-containing neurons and disease duration or the number of skein-containing neurons.[11] Previous ultrastructural

studies have shown that BBs were observed in and around the skein-like inclusions.[6, 8, 10] Moreover, Y 27632 bundles of filaments, which resembled those found in the skein-like inclusions were observed inside and around the BBs.[7, 10] We showed that TDP-43-immunoreactive filamentous structures were observed in and around the early stage BBs and that TDP-43 was not associated with advanced stage BBs. It is likely that BB formation is more aggressive at the earlier stage, whereas the formation of TDP-43 inclusions is continuous in the disease process of ALS. Cystatin C, a cysteine protease inhibitor involved in lysosomal and endosomal protein degradation,[15, 28] is a marker of BBs and is localized to the vesicular structures of

BBs.[29] In normal conditions, the amount of cystatin C is enough to inhibit cysteine protease activities, such as cathepsins and caspases. In our previous study, we demonstrated a marked decrease in cystatin C immunoreactivity in the cytoplasm of anterior horn cells in ALS.[29] Since TDP-43 can be proteolytically processed by caspase-3, one of the cysteine proteases,[30] the decrease of cystatin C may cause activation of cysteine proteases in anterior horn cells of ALS, leading to cleavage of TDP-43. Native TDP-43 has nuclear localization signals and nuclear export signals, both of which are important for Montelukast Sodium subcellular transport of this protein.[31, 32] TDP-43 is cleaved to generate C-terminal fragments in degenerating neurons in ALS and FTLD-TDP.[3, 33] As C-terminal fragments of TDP-43 might lose the nuclear localization signal, the fragmented TDP-43 remains in the cytoplasm and then forms protein aggregates. It is possible to consider that an increased sequestration of cystatin C into BBs may cause accumulation and aggregation of pathological TDP-43 in the anterior horn cells in ALS. There is a statistically significant relationship in the occurrence between BBs and TDP-43 inclusions. Although BBs and TDP-43 inclusions are morphologically and antigenically distinct from each other, these two inclusions may participate synergistically in the disease process of ALS. This work was supported by JSPS KAKENHI (F.M., K.W.