Expression of MicroRNA-200a/b/c in the Mediobasal Hypothalamic Nuclei with Aging.

BACKGROUND: MicroRNAs (miRNAs) belong to small non-coding RNAs that coordinate the expression of cellular genes at the post-transcriptional level. The hypothalamus is a key regulator of homeostasis, biological rhythms and adaptation to different environmental factors. It also participates in the aging regulation. Variations in miRNA expression in the hypothalamus can affect the aging process. OBJECTIVE: Our objective of this study is to examine the expression of miR-200a-3p, miR-200b-3p, miR-200c-3p in the dorsomedial (DMN), ventromedial (VMN) and arcuate (ARN) nuclei of the hypothalamus in male and female rats during aging. METHODS: The expression of miR-200a-3p, miR-200b-3p, and miR-200c-3p in DMN, VMN and ARN was studied by qPCR-RT. The results were presented using the 2-ΔΔCq algorithm. RESULTS: The expression of miR-200a-3p, miR-200b-3p, miR-200c-3p microRNAs decreases with aging in the DMN of males and in the VMN of females. The level of miR-200b-3p expression decreased in aged males in the VMN and females in the DMN. The expression of miR-200c-3p declined in aged males in the ARN and in females in the DMN. The expression of miR-200a-3p, miR-200b-3p, and miR-200c-3p did not change in females in the ARN in aging. CONCLUSION: We found a decrease in the expression of members of the miR-200a-3p, miR-200b-3p, and miR-200c-3p in the tuberal hypothalamic nuclei and their sex differences in aging rats.

Neuronal nitric oxide synthase and calbindin expression in sympathetic preganglionic neurons following capsaicin treatment.

Along with well-known data on the neurochemical mechanisms of nociceptor activation, there are still no clear data regarding changes in the cellular composition and morphological characteristics of spinal preganglionic neurons (SPN) after capsaicin treatment. The mechanism of capsaicin toxicity differs in developing and mature nerve cells. This study aimed to determine the number of SPN in the autonomic nuclei on spinal cord (SC) sections and their cross-sectional area, the localization, percentage, and profile area of SPN containing neuronal nitric oxide synthase (nNOS) and calbindin (CB) in the thoracic SC of rats of different ages (from birth to 1-year-old) after capsaicin treatment. Neonatal capsaicin treatment generally decreased the cross-sectional area of the SPN pericarya. However, the cross-sectional area of the CB-immunoreactive (IR) SPN increased in the central autonomic area in rats aged 10-30 days old after capsaicin treatment. The number of SPN decreased only in the central autonomic area of rats aged <20 days. The proportion of nNOS-IR neurons remained steady and did not change during development. The cross-sectional area of nNOS-IR SPN in capsaicin-treated rats was less than that in control rats. The results obtained will promote further studies on the mechanisms of sensory processing in the SC and the development of the sympathetic nervous system.

Ontogenetic Changes in the Expression of the Lin28 Protein in the Rat Hypothalamic Tuberal Nuclei.

The hypothalamus is a primary regulator of homeostasis, biological rhythms and adaptation to different environment factors. It also participates in the aging regulation. The expression of neurons containing Lin28 was studied by immunohistochemistry in male rats aged 2, 6, 12, and 24 months in the tuberal region of the rat hypothalamus. We have shown for the first time the presence of Lin28-immunoreactive (IR) neurons in the ventromedial nucleus (VMH) and their absence in the dorsomedial and arcuate nuclei in all studied animals. With aging, the percentage of Lin28-IR neurons increases from 37 ± 4.7 in 2-month-old rat until 76 ± 4.6 in 6-month-old and further decreases to 41 ± 7.3 in 12-month-old rat and 28 ± 5.5 in 24-month-old rats. Many VMH Lin28-IR neurons colocalized components of insulin signaling including mTOR, Raptor, PI3K and Akt. The percentage of Lin28/Akt-IR neurons was maximal in 6-month-old and 1-year-old rats compared to 2-month-old and 2-year-old animals. The proportion of Lin28/PI3K-IR neurons significantly increased from 77 ± 1.2 in 2-month-old rat until 99 ± 0.3 in 24-month-old rats and 96-99% of Lin28-IR neurons colocalized mTOR and mTORC1 component Raptor without statistically significant differences in all studied age groups. Thus, Lin28 expresses only in the VMH neurons of the tuberal nuclei of the hypothalamus and the Lin 28 expression changes during the development together with the components of PI3K-Akt-mTOR signaling.

Changes of nNOS expression in the tuberal hypothalamic nuclei during ageing.

The hypothalamus is the most important integrator of autonomic and endocrine regulation in the body and it also has a fundamental role in ageing development and lifespan control. In order to better understand the role of NO-ergic system in the hypothalamic regulation of ageing, the purpose of this study was to investigate the expression of neuronal nitric oxide synthase (nNOS) in the arcuate (ARC), ventromedial (VMH) and dorsomedial (DMH) hypothalamic nuclei in young (2-3-month-old) and old (24-month-old) male and female rats using immunohistochemistry and western blot analysis. In young animals, only single nNOS-immunoreactive (IR) neurons were detected in ARC, and nNOS-IR neurons were found in the VMH (19 ± 3.2% in females and 14.5 ± 2.6% in males) and DMH (17 ± 4.0% in females and 21 ± 2.8% in males). In aged animals, the number of nNOS-IR neurons increased in all studied nuclei, including ARC (36 ± 3.1% in females and 33.5 ± 3.7% in males), VMH (83 ± 4.3% in females and 58 ± 2.1% in males) and DMH (57 ± 1.9% in females and 54 ± 1.8% in males). The expression of nNOS also significantly increased in the ARC, VMH and DMH during ageing by western blot analysis. In conclusion, ageing is accompanied by increasing of nNOS expression in the hypothalamus and this process is related to regions involved in the control of feeding behavior.

Development of nNOS-positive neurons in the rat sensory ganglia after capsaicin treatment.

To gain a better understanding of the neuroplasticity of afferent neurons during postnatal ontogenesis, the distribution of neuronal nitric oxide synthase (nNOS) immunoreactivity was studied in the nodose ganglion (NG) and Th2 and L4 dorsal root ganglia (DRG) from vehicle-treated and capsaicin-treated female Wistar rats at different ages (10-day-old, 20-day-old, 30-day-old, and two-month-old). The percentage of nNOS-immunoreactive (IR) neurons decreased after capsaicin treatment in all studied ganglia in first 20 days of life, from 55.4% to 36.9% in the Th2 DRG, from 54.6% to 26.1% in the L4 DRG and from 37.1% to 15.0% in the NG. However, in the NG, the proportion of nNOS-IR neurons increased after day 20, from 11.8% to 23.9%. In the sensory ganglia of all studied rats, a high proportion of nNOS-IR neurons bound isolectin B4. Approximately 90% of the sensory nNOS-IR neurons bound to IB4 in the DRG and approximately 80% in the NG in capsaicin-treated and vehicle-treated rats. In 10-day-old rats, a large number of nNOS-IR neurons also expressed TrkA, and the proportion of nNOS(+)/TrkA(+) neurons was larger in the capsaicin-treated rats compared with the vehicle-treated animals. During development, the percentage of nNOS(+)/TrkA(+) cells decreased in the first month of life in both groups. The information provided here will also serve as a basis for future studies investigating mechanisms of sensory neuron development.