A model of traumatic brain injury in rats is influenced by neuroprotection of diurnal variation which improves motor behavior and histopathology in white matter myelin

Traumatic brain injury (TBI) represents a significant public health concern and has been associated with high rates of morbidity and mortality. TBI generates two types of brain damage: primary and secondary. Secondary damage originates a series of pathophysiological processes, which include metabolic crisis, excitotoxicity, and neuroinflammation, which have deleterious consequences for neuronal function. However, neuroprotective mechanisms are also activated. The balance among these tissue responses, and its variations throughout the day determines the fate of the damage tissue. We have demonstrated less behavioral and morphological damage when a rat model of TBI was induced during the light hours of the day. Moreover, here we show that rats subjected to TBI in the dark lost less body weight than those subjected to TBI in the light, despite no change in food intake. Besides, the rats subjected to TBI in the dark had better performance in the beam walking test and presented less histological damage in the corpus callosum and the cingulum bundle, as shown by the Klüver-Barrera staining. Our results suggest that the time of day when the injury occurs is important. Thus, this data should be used to evaluate the pathophysiological processes of TBI events and develop better therapies.

NaStEP, an essential protein for self-incompatibility in Nicotiana, performs a dual activity as a proteinase inhibitor and as a voltage-dependent channel blocker

The S-specific pollen rejection response in Nicotiana depends on the interaction between S-RNase and a suite of SLF proteins. However, the biochemical pathway requires other essential proteins. One of them is the stigmatic protein NaStEP, which belongs to the Kunitz-type protease inhibitor family. Within the pollen tubes, NaStEP is a positive regulator of HT-B stability, likely inhibiting its degradation and, additionally, interacts with NaSIPP, a mitochondrial phosphate carrier. To gain a deeper understanding of the biochemical role of NaStEP in pollen rejection, we evaluated whether the activity of NaStEP as protease inhibitor is specific to a particular type of protease and whether it has the function of a voltage-dependent channel (VDC) blocker. Our findings indicate that, in vitro, NaStEP inhibits a subtilisin-like protease in an irreversible manner, but not other proteases, such as thermolysin and papain. Furthermore, we found that subtilisin processes the native NaStEP (24 kDa) into two lower molecular weight peptides of 21 and 14 kDa. Moreover, when we incubated NaStEP along with Xenopus leavis oocytes expressing the voltage-dependent potassium channel Kv 1.3, the current was blocked, indicating that NaStEP acts as a VDC blocker. These data allow us to propose NaStEP acts as a key molecule with two functions, one protecting HT-B from degradation by inhibiting a subtilisin-like protease and the second one by forming a complex with a mitochondrial VDC that could destabilize the mitochondria to trigger cell death, which would reinforce S-specific pollen rejection in Nicotiana.

Novel TASK channels inhibitors derived from dihydropyrrolo[2,1-a]isoquinoline

TASK channels belong to the family of K(+) channels with 4 transmembrane segments and 2 pore domains (4TM/2P) per subunit. These channels have been related to apoptosis in cerebellar granule neurons (CGN), as well as cancer in other tissues. TASK current is regulated by hormones, neurotransmitters, anesthetics and divalent cations, which are not selective. Recently, there has been found some organic compounds that inhibit TASK current selectively. In order to find other modulators, we report here a group of five dihydropyrrolo[2,1-a]isoquinolines (DPIs), four of them with putative anticancer activity, that were evaluated on TASK-1 and TASK-3 channels. The compounds 1, 2 and 3 showed IC50 < 320 μM on TASK-1 and TASK-3, intermediate activity on TASK-1/TASK-3 heterodimer, moderate effect over hslo and TREK-1 (500 μM), and practically not inhibition on Shaker-IR, herg and IRK2.1 potassium channels, when they were expressed heterologously in Xenopus laevis oocytes. In rat CGN, 500 μM of these three compounds induced a decrement by >39% of the TASK-carried leak current. Finally, only compound 1 showed significant protection (∼36%) against apoptotic death of CGN induced by K(+) deprivation. These results suggest that DPI compounds could be potential candidates for designing new selective inhibitors of TASK channels.