Descripción: Messenger RNA (mRNA) for enzymes involved in adrenal steroid biosynthesis are expressed in the brain, and the coded enzymes have been shown to be active. The expression of mRNA for the cytochrome P-450 enzyme aldosterone synthase, crucial for the final step in the synthesis of aldosterone and the synthesis of aldosterone was studied in several anatomic areas of the rat brain. Expression of the mRNA for the aldosterone synthase was demonstrated by RT-PCR/Southern blot in adrenal, aorta, hypothalamus, hippocampus, amygdala, cerebrum, and cerebellum. Incubation of brain minces from intact and adrenalectomized rats demonstrated the synthesis of corticosterone and aldosterone from endogenous precursors. Incubations of brain mince, with [1,23H]-deoxycorticosterone, followed by extraction and three different successive TLCs, demonstrated the presence of labeled aldosterone, corticosterone, and 18-hydroxy-deoxycorticosterone. Incubation, in the presence of 10 μM cortisol or metyrapone, inhibited the synthesis of aldosterone or both aldosterone and corticosterone, respectively. These studies indicate that the rat brain has the enzymatic machinery for the synthesis of adrenal corticosteroids and is capable of synthesizing aldosterone. Aldosterone synthesized in the brain might play a paracrine role in the regulation of blood pressure.

Descripción: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by a gradual loss of motoneurons. The majority of ALS cases are associated with a sporadic form whose etiology is unknown. Several pieces of evidence favor autoimmunity as a potential contributor to sporadic ALS pathology. To gain understanding concerning possible antigens interacting with IgGs from sporadic ALS patients (ALS-IgGs), we studied immunoreactivity against neuromuscular junction (NMJ), spinal cord and cerebellum of mice with and without the Ca V2.1 pore-forming subunit of the P/Q-type voltage-gated calcium (Ca 2+) channel. ALS-IgGs showed a strong reactivity against NMJs of wild-type diaphragms. ALS-IgGs also increased muscle miniature end-plate potential frequency, suggesting a functional role for ALS-IgGs on synaptic signaling. In support, in mice lacking the Ca V2.1 subunit ALS-IgGs showed significantly reduced NMJ immunoreactivity and did not alter spontaneous acetylcholine release. This difference in reactivity was absent when comparing N-type Ca 2+ channel wild-type or null mice. These results are particularly relevant because motoneurons are known to be early pathogenic targets in ALS. Our findings add further evidence supporting autoimmunity as one of the possible mechanisms contributing to ALS pathology. They also suggest that serum autoantibodies in a subset of ALS patients would interact with NMJ proteins down-regulated when P/Q-type channels are absent. © 2011 International Society for Neurochemistry.

Descripción: In this report we describe our studies on intracellular signals that mediate neurite outgrowth and long-term survival of cerebellar granule cells. The effect of voltage-gated calcium channel activation on neurite complexity was evaluated in cultured cerebellar granule cells grown for 48 h at low density; the parameter measured was the fractal dimension of the cell. We explored the contribution of two intracellular pathways, Ca2+ calmodulin-dependent protein kinase II and mitogen-activated protein kinase kinase (MEK1), to the effects of high [K+]e under serum-free conditions. We found that 25 mM KCI (25K) induced an increase in calcium influx through L subtype channels. In neurones grown for 24-48 h under low-density conditions, the activation of these channels induced neurite outgrowth through the activation of Ca2+ calmodulin-dependent protein kinase II. This also produced an increase in long-term neuronal survival with a partial contribution from the MEK1 pathway. We also found that the addition of 25K increased the levels of the phosphorylated forms of Ca2+ calmodulin-dependent protein kinase II and of the extracellular signal-regulated kinases 1 and 2. Neuronal survival under resting conditions is supported by the MEK1 pathway. We conclude that intracellular calcium oscillations can triggered different biological effects depending on the stage of maturation of the neuronal phenotype. Ca2+ calmodulin-dependent protein kinase II activation determines the growth of neurites and the development of neuronal complexity.