Maintaining protein homeostasis is vital to cell viability, with numerous studies demonstrating a role for proteasome inhibition occurring during the aging of a variety of tissues, and presumably contributing to the disruption of cellular homeostasis during aging. In the present study we sought to elucidate the differences between neurons and astrocytes in regards to basal levels of protein synthesis, proteasome-mediated protein degradation, and sensitivity to cytoxicity following proteasome inhibitor treatment. In these studies we demonstrate that neurons have an increased vulnerability, as compared to astrocyte cultures, to proteasome inhibitor-induced cytotoxicity. No significant difference was observed between these two cell types in regards to the basal rates of protein synthesis, or basal rates of protein degradation, in the pool of short-lived proteins. Following proteasome inhibitor treatment neuronal crude lysates were observed to undergo greater increases in the levels of ubiquitinated and oxidized proteins, and selectively exhibited increased levels of newly synthesized proteins accumulating within the insoluble protein pool, as compared to astrocytes. Together, these data suggest a role for increased oxidized proteins and sequestration of newly synthesized proteins to the insoluble protein pool, as potential mediators of the selective neurotoxicity following proteasome inhibitor treatment. The implications for neurons exhibiting increased sensitivity to acute proteasome inhibitor exposure, and the corresponding changes in protein homeostasis observed following proteasome inhibition, are discussed in the context of both aging and age-related disorders of the nervous system.

Thymoquinone, a naturally derived agent, has been shown to possess antioxidant, antiproliferative and proapoptotic activities. In the present study, we explored thymoquinone effects on the proteasomal complex, the major system involved in the removal of damaged, oxidized and misfolded proteins. In purified 20S complexes, subunit‐dependent and composition‐dependent inhibition was observed, and the chymotrypsin‐like and trypsin‐like activities were the most susceptible to thymoquinone treatment. U87 MG and T98G malignant glioma cells were treated with thymoquinone, and 20S and 26S proteasome activity was measured. Inhibition of the complex was evident in both cell lines, but predominantly in U87 MG cells, and was accompanied by accumulation of ubiquitin conjugates. Accumulation of p53 and Bax, two proteasome substrates with proapoptotic activity, was observed in both cell lines. Our results demonstrate that thymoquinone induces selective and time‐dependent proteasome inhibition, both in isolated enzymes and in glioblastoma cells, and suggest that this mechanism could be implicated in the induction of apoptosis in cancer cells.

Background Infectious abortion in ruminants is a problem in animal husbandry worldwide. It is important to obtain a diagnosis, to make sure that proper control measures can be instituted, but most abortion cases remain without an etiologic diagnosis. This report describes the presence of Arcobacter species and several neglected opportunistic abortifacient agents in ruminant abortion cases showing or not co-infections among at least one of the major recognized protozoal, fungal, bacterial and viral abortifacient agents. Results A total of 67 fetuses (55 cattle and 12 goats) and just one placenta (cattle) were considered. Among the most common abortive agents, Neospora caninum (19,4%), followed by Chlamydophila abortus (4,5%), Listeria monocytogenes 1/2a (2,98%), Bovine Viral Diarrhea Virus type 1b (2,98%), Bovine herpesvirus 4 (2,98%), and Aspergillus spp. (2,98%) were detected. The isolated neglected opportunistic bacteria include Escherichia coli , Acinetobacter lwoffii , Staphylococcus spp., Streptococcus spp., Streptococcus uberis , Streptococcus suis , Trueperella pyogenes, Mannheimia haemolytica , Bacillus cereus and Nocardia spp. Other bacterial species, not associated with abortion by literature, but described as causes of diseases occurring sporadically both in humans and animals, were also detected. Three Arcobacter strains, namely two A. skirrowii and one A. cryaerophilus , were isolated from 3 bovine aborted fetuses, and A. butzleri was isolated from the placenta. Conclusions A not negligible isolation of Arcobacter species and other neglected abortifacient agents has to be mentioned, with prevalences that seem to be emerging and replacing or co-placing the major infectious players in bovine and caprine reproductive failure due to abortion disease, even if further studies investigating the aetiological power and transmission routes are needed in order to define the role of these microrganisms in ruminant abortion.

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