Multispectral optoacoustic tomography (MSOT): Monitoring neurovascular changes in a mouse repetitive traumatic brain injury model.

BACKGROUND: Evidence suggests that mild TBI injuries, which comprise > 75% of all TBIs, can cause chronic post-concussive symptoms, especially when experienced repetitively (rTBI). rTBI is a major cause of cognitive deficit in athletes and military personnel and is associated with neurovascular changes. Current methods to monitor neurovascular changes in detail are prohibitively expensive and invasive for patients with mild injuries. NEW METHOD: We evaluated the potential of multispectral optoacoustic tomography (MSOT) to monitor neurovascular changes and assess therapeutic strategies in a mouse model of rTBI. Mice were subjected to rTBI or sham via controlled cortical impact and administered pioglitazone (PG) or vehicle. Oxygenated and deoxygenated hemoglobin were monitored using MSOT. Indocyanine green clearance was imaged via MSOT to evaluate blood-brain-barrier (BBB) integrity. RESULTS: Mice subjected to rTBI show a transient increase in oxygenated/total hemoglobin ratio which can be mitigated by PG administration. rTBI mice also show BBB disruption shortly after injury and reduction of oxygenated/total hemoglobin in the chronic stage, neither of which were affected by PG intervention. COMPARISON WITH EXISTING METHODS: MSOT imaging has the potential as a noninvasive in vivo imaging method to monitor neurovascular changes and assess therapeutics in mouse models of rTBI. In comparison to standard methods of tracking inflammation and BBB disruption, MSOT can be used multiple times throughout the course of injury without the need for surgery. Thus, MSOT is especially useful in research of rTBI models for screening therapeutics, and with further technological improvements may be extended for use in rTBI patients.

MicroRNA-301a mediated regulation of Kv4.2 in diabetes: identification of key modulators.

Diabetes is a metabolic disorder that ultimately results in major pathophysiological complications in the cardiovascular system. Diabetics are predisposed to higher incidences of sudden cardiac deaths (SCD). Several studies have associated diabetes as a major underlying risk for heart diseases and its complications. The diabetic heart undergoes remodeling to cope up with the underlying changes, however ultimately fails. In the present study we investigated the changes associated with a key ion channel and transcriptional factors in a diabetic heart model. In the mouse db/db model, we identified key transcriptional regulators and mediators that play important roles in the regulation of ion channel expression. Voltage-gated potassium channel (Kv4.2) is modulated in diabetes and is down regulated. We hypothesized that Kv4.2 expression is altered by potassium channel interacting protein-2 (KChIP2) which is regulated upstream by NFkB and miR-301a. We utilized qRT-PCR analysis and identified the genes that are affected in diabetes in a regional specific manner in the heart. At protein level we identified and validated differential expression of Kv4.2 and KChIP2 along with NFkB in both ventricles of diabetic hearts. In addition, we identified up-regulation of miR-301a in diabetic ventricles. We utilized loss and gain of function approaches to identify and validate the role of miR-301a in regulating Kv4.2. Based on in vivo and in vitro studies we conclude that miR-301a may be a central regulator for the expression of Kv4.2 in diabetes. This miR-301 mediated regulation of Kv4.2 is independent of NFkB and Irx5 and modulates Kv4.2 by direct binding on Kv4.2 3'untranslated region (3'-UTR). Therefore targeting miR-301a may offer new potential for developing therapeutic approaches.

Afobazole modulates microglial function via activation of both sigma-1 and sigma-2 receptors.

Microglial cells play a critical role in the neuroinflammatory response that accompanies various diseases of the central nervous system, such as ischemic stroke, and ATP is a major signaling molecule regulating the response of these cells to these pathophysiological conditions. Experiments were carried out to determine the effects of afobazole on microglial function and to identify the molecular mechanisms by which afobazole affects microglial cells. Afobazole was found to inhibit migration of microglial cells in response to ATP and UTP chemoattraction in a concentration-dependent manner. Inhibition of either σ-1 or σ-2 receptors decreased the effects of afobazole on microglia. In addition to inhibiting microglial cell migration, activation of σ receptors by afobazole decreased intracellular calcium elevation produced by focal application of ATP and UTP in isolated microglial cells. Furthermore, afobazole blocked membrane currents elicited by rapid application of ATP in microglial cells. Taken together, our data indicate that afobazole inhibits microglial response to P2Y and P2X purinergic receptor activation by functioning as a pan-selective σ-receptor agonist. In addition to modulating response to purinergic receptor activation, the effects of afobazole on microglial survival during in vitro ischemia were assessed. Application of afobazole during in vitro ischemia decreased microglial cell death during the ischemic episode and after a 24-h recovery period. Moreover, when afobazole was only applied after the ischemic episode, a significant enhancement in cell survival was still observed. Thus, afobazole acts via σ receptors to decrease microglial response to ATP and provides cytoprotection during and after ischemia.