Localization of pepstatin's inhibitory action during Fc-mediated antibody internalization: possible implications for antibody-mediated viral transmission

Trehalose Reduces the Secreted Beta-Amyloid Levels in Primary Neurons Independently of Autophagy Induction

The disaccharide trehalose was described as possessing relevant neuroprotective properties as an mTORC1-independent inducer of autophagy, with the ability to protect cellular membranes and denaturation, resulting from desiccation, and preventing the cellular accumulation of protein aggregates. These properties make trehalose an interesting therapeutic candidate against proteinopathies such as Alzheimer’s disease (AD), which is characterized by deposits of aggregated amyloid-beta (Aβ) and hyperphosphorylated tau. In this study, we observed that trehalose was able to induce autophagy in neurons only in the short-term, whereas long-term treatment with trehalose provoked a relevant anti-amyloidogenic effect in neurons from an AD mouse model that was not mediated by autophagy. Trehalose treatment reduced secreted Aβ levels in a manner unrelated to its intracellular accumulation or its elimination through endocytosis or enzymatic degradation. Moreover, the levels of Aβ precursor protein (APP) and beta-secretase (BACE1) remained unaltered, as well as the proper acidic condition of the endo-lysosome system. Instead, our results support that the neuroprotective effect of trehalose was mediated by a reduced colocalization of APP and BACE1 in the cell, and, therefore, a lower amyloidogenic processing of APP. This observation illustrates that the determination of the mechanism, or mechanisms, that associate APP and BACE is a relevant therapeutic target to investigate.

Calcium signaling pathways mediating synaptic potentiation triggered by amyotrophic lateral sclerosis IgG in motor nerve terminals

Sporadic amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that affects particularly motoneurons. Several pieces of evidence suggested the involvement of autoimmune mechanisms mediated by antibodies in ALS. However, the significance of those antibodies in the disease and the underlying mechanisms are unknown. Here we showed that IgG purified from a group of sporadic ALS patients, but not familial ALS patients, specifically interact with the presynaptic membrane of motoneurons through an antigen-antibody interaction and modulated synaptic transmission. Immunoreactivity against nerve terminals showed strong correlation with synaptic modulation ability. In addition, several controls have ruled out the possibility for this synaptic modulation to be mediated through proteases or nonspecific effects. Effective IgG potentiated both spontaneous and asynchronous transmitter release. Application of pharmacological inhibitors suggested that activation of this increased release required a nonconstitutive Ca2+ influx through N-type (Cav2.2) channels and phospholipase C activity and that activation of IP3 and ryanodine receptors were necessary to both activate and sustain the increased release. Consistent with the notion that ALS is heterogeneous disorder, our results reveal that, in approximately 50% of ALS patients, motor nerve terminals constitutes a target for autoimmune response.

Placental cytokine and chemokine production in HIV-1-infected women: trophoblast cells show a different pattern compared to cells from HIV-negative women

In utero transmission of HIV-1 has been demonstrated and may account for around 10-20% of all materno-fetal HIV-1 transmission. The possible routes for such transmission are transannexial or transplacental. In both cases, the microenvironment (cytokines and chemokines) at the placental interface could be an important regulatory factor in viral transmission. We therefore performed explant cultures of placental villi, and isolated purified trophoblasts, from term placentae obtained from HIV-1-seropositive and HIV-1-seronegative women in order to assess and compare the cytokine and chemokine secretion profiles using ELISA and semiquantitative RT-PCR. No major differences could be seen in the secretions of cytokines and chemokines at the level of whole placental tissue in HIV-1-positive and HIV-1-negative women. However, variations were observed in the expression of inflammatory cytokines and chemokines from trophoblastic cells, depending on the status of HIV-1 infection of the mothers but not the babies, all of which remained uninfected. The significance of these data is discussed.