Alejandro Lomniczi

In 2013, considerable progress was made towards deciphering the molecular foundations of puberty. Loss of transcriptional repression was identified as a core mechanism underlying the onset of puberty, and this loss was found to be precipitated by epigenetic cues. It was also discovered that nutritional deprivation delays puberty by repressing reproductive neuroendocrine function.

The aim of the present work was to study the effect of long-term cyclosporine (CSA) administration on norepinephrine (NE) metabolism and adrenergic-evoked secretion in the rat submandibular gland (SMG). Dose-response curves to adrenergic agonists (methoxamine, isoproterenol, NE) were performed in control and CSA (10 and 30 mg/kg every 2 days for 1 month)-treated rats after SMG duct cannulation. In SMG tissue neuronal NE uptake, release, synthesis and endogenous content were determined. In addition phosphoinositide intracellular signaling was also investigated. CSA administration caused an increase in salivary secretion evoked by methoxamine (alpha-adrenergic agonist) and NE but failed to modify salivation evoked by beta-adrenergic stimulation (isoproterenol). Long-term CSA administration decreased NE release and synthesis whereas it enhanced the amine uptake and phosphoinositide hydrolysis in the SMG. The administration of CSA for 30 days induced salivary gland sensitization likely mediated by diminished adrenergic input. Present results suggest that the decreased sympathetic activity evoked by long-term CSA administration in the rat SMG may lead to sensitization of the gland supported by increased phosphoinositide hydrolysis and enhanced adrenergic-evoked salivation.

Since nitric oxide has been found to control the function of many organs of the body by the non-adrenergic, non-cholinergic branch of the autonomic nervous system, we hypothesized that it might play a role in salivary secretion. Therefore, we investigated the distribution of nitric oxide synthase (NOS) throughout the submaxillary gland and also studied the ability of inhibitors of NOS to interfere with salivation induced by a cholinergic agonist, metacholine, and by a polypeptide, substance P. The secretory responses were determined in rats anesthetized with chlorolose following intravenous injection of the various pharmacological agents. There was no basal flow of saliva and dose-response curves were obtained by sequential intravenous injection of increasing doses of the drugs. Then, in the same animal, the same dose-response curves were performed in the presence of NOS inhibitors. L-Nitro-arginine-methyl-ester (L-NAME; 20 mg/kg) produced an over 50% inhibition of the dose-related salivation induced by metacholine. Similar results were produced with L-NG-monomethyl-L-arginine (L-NMMA; 5 mg/kg). The salivation induced by much lower molar doses of substance P was dramatically greater than that obtained with metacholine. The response to substance P was almost completely inhibited by L-NMMA at the lowest dose (0.3 mg/kg), but at higher doses (1 mg/kg), the inhibition was only around 60% and at the highest dose (3 mg/kg) only about 20%. In control rats, there were roughly equal amounts of calcium-dependent and calcium-independent NOS in the gland at this time. At the end of the experiment, the effect of the inhibitor of NOS, L-NMMA, on the NOS activity in the submandibular gland was determined. At this time, the Ca2+-dependent NOS was decreased and the Ca2+-independent NO was increased. The prior injection of L-NMMA reduced calcium-dependent NOS activity by approximately 70% but calcium-independent activity by only 30%. These results indicate that, at least at the end of the experiment, the blockade of NOS imposed by NMMA was incomplete. This could account in part for the failure of the inhibitors to block completely the stimulatory effect of the two secretagogues. Analysis of the distribution of NOS in the salivary gland revealed that it was not present in the acinar cells, but in neural terminals within the gland and also in the ductile system which contained neural (n) NOS in the apical membrane of the excretory and striated ducts, the cytoplasm of granular convoluted tubules and, to a lesser extent, in the cytoplasm of excretory and striated ducts. Macrophage (inducible) NOS was also found not only in the macrophages, but also in the tubules and ducts. Since drugs were used that would act on the receptors in the gland, the role of NO in our conditions is probably mediated by nNOS and iNOS in the ductile and tubular structures. Since iNOS would already be active, it is unlikely to play a role in this acute secretory activity. Rather the nNOS in these non-neural cells is probably activated by muscarinic or K1 receptors by metacholine and substance P, respectively, leading to an increase in intracellular free calcium that activates NOS leading to the generation of cGMP that opens ion channels to initiate the secretory process.

Kisspeptin, the product of the KiSS1 gene, has emerged as a key component of the mechanism by which the hypothalamus controls puberty and reproductive development. It does so by stimulating the secretion of gonadotropin releasing hormone (GnRH). Little is known about the transcriptional control of the KiSS1 gene. Here we show that a set of proteins postulated to be upstream

Mammalian puberty requires activation of luteinizing hormone–releasing hormone (LHRH) neurons. In turn, these neurons are controlled by transsynaptic and glia-to-neuron communication pathways, which employ diverse cellular proteins for proper function. We have now used a high throughput relative quantitative proteomics technique to identify such proteins. We selected the method of two-dimensional liquid chromatography tandem mass spectrometry (2DLC–MS/MS) and cleavable isotope-coded