Establishment of a method to expose and measure pollution in excised porcine skin with electron paramagnetic resonance spectroscopy

Health problems associated with the amount of air pollutants are increasing worldwide. Pollution damages not only the lungs; it also has an impact on skin health and is co-responsible for the development of skin diseases. Anti-pollution products are on the rise in the cosmetic market but so far, there is no established method to directly assess the impact of pollution on the skin and to test the efficacy of anti-pollution products. To address this problem, two different chambers were developed for the reproducible exposure to realistic air pollutant concentrations. One chamber for the exclusive use of excised skin and hair samples, the second chamber for ex vivo and in vivo measurements. Measurements of nicotine next to the investigated skin area allow conclusions to be drawn on the particle concentration to which the skin is exposed. Electron paramagnetic resonance spectroscopy, which enables the detection of free radicals in different systems, was applied to assess the hazard potential of pollution in the skin. A direct proof of the formation of free radicals in the skin by the model pollutant cigarette smoke could be demonstrated. An additional application of UV irradiation even increased the formation of free radicals in the skin seven-fold (sum parameter). Depending on the question of interest, the use of different spin probes allows various assessments of the radical formation in skin: the amount of radicals but also the antioxidant status of the microenvironment can be estimated. Using two exposure chambers, the direct formation of oxidative stress by cigarette smoke on ex vivo skin, with and without additional UV exposure, could be reproducibly examined. This measurement method is promising for the assessment of anti-pollution products and could allow a direct causal connection between pollutant, effect on the skin and the protective function of skin care products.

Inhibiting Kiss1 Neurons With Kappa Opioid Receptor Agonists to Treat Polycystic Ovary Syndrome and Vasomotor Symptoms

CONTEXT

Recent evidence suggests that vasomotor symptoms (VMS) or hot flashes in the postmenopausal reproductive state and polycystic ovary syndrome (PCOS) in the premenopausal reproductive state emanate from the hyperactivity of Kiss1 neurons in the hypothalamic infundibular/arcuate nucleus (KNDy neurons).

OBJECTIVE

We demonstrate in 2 murine models simulating menopause and PCOS that a peripherally restricted kappa receptor agonist (PRKA) inhibits hyperactive KNDy neurons (accessible from outside the blood-brain barrier) and impedes their downstream effects.

DESIGN

Case/control.

SETTING

Academic medical center.

PARTICIPANTS

Mice.

INTERVENTIONS

Administration of peripherally restricted kappa receptor agonists and frequent blood sampling to determine hormone release and body temperature.

MAIN OUTCOME MEASURES

LH pulse parameters and body temperature.

RESULTS

First, chronic administration of a PRKA to bilaterally ovariectomized mice with experimentally induced hyperactivity of KNDy neurons reduces the animals' elevated body temperature, mean plasma LH level, and mean peak LH per pulse. Second, chronic administration of a PRKA to a murine model of PCOS, having elevated plasma testosterone levels and irregular ovarian cycles, suppresses circulating levels of LH and testosterone and restores normal ovarian cyclicity.

CONCLUSION

The inhibition of kisspeptin neuronal activity by activation of kappa receptors shows promise as a novel therapeutic approach to treat both VMS and PCOS in humans.

Sex-specific pubertal and metabolic regulation of Kiss1 neurons via Nhlh2

Hypothalamic Kiss1 neurons control gonadotropin-releasing hormone release through the secretion of kisspeptin. Kiss1 neurons serve as a nodal center that conveys essential regulatory cues for the attainment and maintenance of reproductive function. Despite this critical role, the mechanisms that control kisspeptin synthesis and release remain largely unknown. Using Drop-Seq data from the arcuate nucleus of adult mice and in situ hybridization, we identified Nescient Helix-Loop-Helix 2 (Nhlh2), a transcription factor of the basic helix-loop-helix family, to be enriched in Kiss1 neurons. JASPAR analysis revealed several binding sites for NHLH2 in the Kiss1 and Tac2 (neurokinin B) 5' regulatory regions. In vitro luciferase assays evidenced a robust stimulatory action of NHLH2 on human KISS1 and TAC3 promoters. The recruitment of NHLH2 to the KISS1 and TAC3 promoters was further confirmed through chromatin immunoprecipitation. In vivo conditional ablation of Nhlh2 from Kiss1 neurons using Kiss1Cre:Nhlh2fl/fl mice induced a male-specific delay in puberty onset, in line with a decrease in arcuate Kiss1 expression. Females retained normal reproductive function albeit with irregular estrous cycles. Further analysis of male Kiss1Cre:Nhlh2fl/fl mice revealed higher susceptibility to metabolic challenges in the release of luteinizing hormone and impaired response to leptin. Overall, in Kiss1 neurons, Nhlh2 contributes to the metabolic regulation of kisspeptin and NKB synthesis and release, with implications for the timing of puberty onset and regulation of fertility in male mice.

Characterization of the Action of Tachykinin Signaling on Pulsatile LH Secretion in Male Mice

The alternation of the stimulatory action of the tachykinin neurokinin B (NKB) and the inhibitory action of dynorphin within arcuate (ARH) Kiss1 neurons has been proposed as the mechanism behind the generation of gonadotropin-releasing hormone (GnRH) pulses through the pulsatile release of kisspeptin. However, we have recently documented that GnRH pulses still exist in gonadectomized mice in the absence of tachykinin signaling. Here, we document an increase in basal frequency and amplitude of luteinizing hormone (LH) pulses in intact male mice deficient in substance P, neurokinin A (NKA) signaling (Tac1KO), and NKB signaling (Tac2KO and Tacr3KO). Moreover, we offer evidence that a single bolus of the NKB receptor agonist senktide to gonad-intact wild-type males increases the basal release of LH without changing its frequency. Altogether, these data support the dispensable role of the individual tachykinin systems in the generation of LH pulses. Moreover, the increased activity of the GnRH pulse generator in intact KO male mice suggests the existence of compensation by additional mechanisms in the generation of kisspeptin/GnRH pulses.

Tachykinin Signaling Is Required for Induction of the Preovulatory Luteinizing Hormone Surge and Normal Luteinizing Hormone Pulses

Tachykinins (neurokinin A [NKA], neurokinin B [NKB], and substance P [SP]) are important components of the neuroendocrine control of reproduction by direct stimulation of Kiss1 neurons to control GnRH pulsatility, which is essential for reproduction. Despite this role of tachykinins in successful reproduction, knockout (KO) mice for Tac1 (NKA/SP) and Tac2 (NKB) genes are fertile, resembling the phenotype of human patients bearing NKB signaling mutations, who often reverse their hypogonadal phenotype. This suggests the existence of compensatory mechanisms among the different tachykinin ligand-receptor systems to maintain reproduction in the absence of one of them. In order to test this hypothesis, we generated complete tachykinin-deficient mice (Tac1/Tac2KO). Male mice displayed delayed puberty onset and decreased luteinizing hormone (LH) pulsatility (frequency and amplitude of LH pulses) but preserved fertility. However, females did not show signs of puberty onset (first estrus) within 45 days after vaginal opening, they displayed a low frequency (but normal amplitude) of LH pulses, and 80% of them remained infertile. Further evaluation identified a complete absence of the preovulatory LH surge in Tac1/Tac2KO females as well as in wild-type females treated with NKB or SP receptor antagonists. These data confirmed a fundamental role of tachykinins in the timing of puberty onset and LH pulsatility and uncovered a role of tachykinin signaling in facilitation of the preovulatory LH surge. Overall, these findings indicate that tachykinin signaling plays a dominant role in the control of ovulation, with potential implications as a pathogenic mechanism and a therapeutic target to improve reproductive outcomes in women with ovulation impairments.

Novel insights into the metabolic action of Kiss1 neurons

Kiss1 neurons are essential regulators of the hypothalamic-pituitary-gonadal (HPG) axis by regulating gonadotropin-releasing hormone (GnRH) release. Compelling evidence suggests that Kiss1 neurons of the arcuate nucleus (Kiss1ARC), recently identified as the hypothalamic GnRH pulse generator driving fertility, also participate in the regulation of metabolism through kisspeptinergic and glutamatergic interactions with, at least, proopiomelanocortin (POMC) and agouti-related peptide (AgRP)/neuropeptide Y (NPY) neurons, located in close apposition with Kiss1ARC. This review offers a comprehensive overview of the recent developments, mainly derived from animal models, on the role of Kiss1 neurons in the regulation of energy balance, including food intake, energy expenditure and the influence of circadian rhythms on this role. Furthermore, the possible neuroendocrine pathways underlying this effect, and the existing controversies related to the anorexigenic action of kisspeptin in the different experimental models, are also discussed.

Hypothalamic Reproductive Endocrine Pulse Generator Activity Independent of Neurokinin B and Dynorphin Signaling

CONTEXT

Kisspeptin-neurokinin B (NKB)-dynorphin neurons are critical regulators of the hypothalamic-pituitary-gonadal axis. NKB and dynorphin are hypothesized to influence the frequency of GnRH pulses, whereas kisspeptin is hypothesized to be a generator of the GnRH pulse. How these neuropeptides interact remains unclear.

OBJECTIVE

To probe the role of NKB in GnRH pulse generation and to determine the interactions between NKB, kisspeptin, and dynorphin in humans and mice with a complete absence of NKB.

DESIGN

Case/control.

SETTING

Academic medical center.

PARTICIPANTS

Members of a consanguineous family bearing biallelic loss-of-function mutations in the gene encoding NKB and NKB-deficient mice.

INTERVENTIONS

Frequent blood sampling to characterize neuroendocrine profile and administration of kisspeptin, GnRH, and naloxone, a nonspecific opioid receptor antagonist used to block dynorphin.

MAIN OUTCOME MEASURES

LH pulse characteristics.

RESULTS

Humans lacking NKB demonstrate slow LH pulse frequency, which can be increased by opioid antagonism. Mice lacking NKB also demonstrate impaired LH secretion, which can be augmented with an identical pharmacologic manipulation. Both mice and humans with NKB deficiency respond to exogenous kisspeptin.

CONCLUSION

The preservation of LH pulses in the absence of NKB and dynorphin signaling suggests that both peptides are dispensable for GnRH pulse generation and kisspeptin responsiveness. However, NKB and dynorphin appear to have opposing roles in the modulation of GnRH pulse frequency.

Characterization of the Role of NKA in the Control of Puberty Onset and Gonadotropin Release in the Female Mouse

The tachykinin neurokinin B (NKB, Tac2) is critical for proper GnRH release in mammals, however, the role of the other tachykinins, such as substance P (SP) and neurokinin A (NKA) in reproduction, is still not well understood. In this study, we demonstrate that NKA controls the timing of puberty onset (similar to NKB and SP) and stimulates LH release in adulthood through NKB-independent (but kisspeptin-dependent) mechanisms in the presence of sex steroids. Furthermore, this is achieved, at least in part, through the autosynaptic activation of Tac1 neurons, which express NK2R (Tacr2), the receptor for NKA. Conversely, in the absence of sex steroids, as observed in ovariectomy, NKA inhibits LH through a mechanism that requires the presence of functional receptors for NKB and dynorphin (NK3R and KOR, respectively). Moreover, the ability of NKA to modulate LH secretion is absent in Kiss1KO mice, suggesting that its action occurs upstream of Kiss1 neurons. Overall, we demonstrate that NKA signaling is a critical component in the central control of reproduction, by contributing to the indirect regulation of kisspeptin release.

SAT-LB070 Tachykinins Are Essential for the Induction of the Preovulatory LH Surge in Mice

Tachykinins (TACs) result from the differential processing of two genes in rodents, Tac1 (encoding substance P (SP) and neurokinin A (NKA)) and Tac2 (encoding NKB). TACs exert their effects in the hypothalamus by acting on different G protein-coupled receptors (GPCRs): NK1R, the receptor of SP, NK2R, the receptor of NKA, and NK3R, the receptor of NKB. We and others have documented a stimulatory role for all these tachykinins in the release of GnRH in the presence of physiological circulating levels of sex steroids. Important cross-reactivity between the TAC ligand-receptor systems has been documented and suggested as a possible cause for the reversal of hypogonadal NKB-signaling deficient patients. In order to test the possible redundancy in the TAC systems, we generated a mouse model of congenital removal of all TACs (Tac1KO/Tac2KO, aka TACKO). This model revealed a sexually dimorphic effect of TACs on puberty onset and fertility. TACKO male mice (n= 14) displayed delayed puberty onset compared with wildtype (WT) littermates, resembling Tac1KO and Tac2KO mice separately, but retained normal fertility. By contrast, TACKO females presented a slight delay in the timing of vaginal opening (VO) -a marker of puberty onset—, compared to controls, but none of the females (n=10) presented signs of first estrus within 30 days after VO, indicating a failure to undergo complete sexual maturation. This was supported by a profound reproductive impairment, as only 20% of the TACKO females that were mated with fertile WT males for 8 weeks delivered pups (and these litters presented a significantly reduced number of pups and significantly larger parturition latency than controls). To test the ability of TACKO females to mount a normal LH surge, a similar cohort of TACKO females (n = 5) was subjected to an LH surge inducing protocol, which evidenced the absence of a detectable preovulatory surge in KO mice. Overall, these data suggest a novel role for TACs as essential players in the induction of the preovulatory LH surge in females, through a redundant mechanism that is only evident in the absence of all TACs, but not in the absence of Tac1 or Tac2, separately. These data further suggest that while TACs participate in the timing of puberty onset in both sexes, they are dispensable for the tonic (pulsatile) release of GnRH/LH as evidenced by the normal fertile phenotype of male TACKO mice. Because preoptic area Kiss1 neurons do not coexpress TACs, these findings strongly support an additional role for caudal hypothalamic (arcuate and ventromedial nuclei) neurons in the control of ovulation. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

OR06-1 Melanocortins Act on Kiss1 Neurons to Regulate Reproduction in Females

Reproduction, controlled by the excitatory action of the neuropeptide kisspeptin, is an energy costly function for the organism and, therefore, it is tightly regulated by metabolic factors. Among those, hypothalamic melanocortins are essential in the control of metabolism. Inactivating mutations in the proopiomelanocortin (Pomc) gene or melanocortin receptor 4 (Mc4r) cause severe obesity and subfertility in humans and mice. However, whether the reproductive impairment is a direct consequence of the lack of melanocortin signaling, or indirect resulting from the obesity phenotype, remains unknown. α-MSH (derived from Pomc) stimulates LH release and this action has been shown to be mediated by Kiss1 neurons. We evaluated the expression of Mc4r in Kiss1 neurons, and using dual fluorescence in situ hybridization (RNAscope), we showed that Kiss1 neurons of the arcuate nucleus (Kiss1^ARC) and the anteroventral periventricular/periventricular nucleus (Kiss1^AVPV/PeN) express Mc4r. Mc4r colocalized with 84% of Kiss1^ARC and with 74% of Kiss1^AVPV/PeN, suggesting that Kiss1 neurons are a direct target of melanocortins. In order to evaluate the involvement of Kiss1 neurons in the reproductive role of melanocortins, we ablated Mc4r specifically from Kiss1 neurons by generating a specific Kiss1-Mc4rKO (Kiss1-cre⁺/Mc4r-lox^+/+) mouse line. We found that Kiss1-Mc4rKO females exhibit disrupted estrous cycles with prolonged diestrous phases and delayed puberty onset compared to their control littermates, without developing obesity during the time of the study. The reproductive phenotype of Kiss1-Mc4rKO males was not affected. When central injections of an Mc4r selective agonist were performed on Kiss1-Mc4rKO intact males and their control littermates, LH levels were significantly increased to the same extend in both groups at 15 min post-injections, suggesting that, in the male, α-MSH controls LH levels through a Kiss1 neuron independent mechanism. Taken together, these results support a direct role of melanocortins on Kiss1 neurons in the control of GnRH release in female mice. Overall, understanding the neuroendocrine mechanisms underlying the metabolic regulation of reproduction will help improve the fertility rates in patients affected by metabolic disturbances. Keywords: Kisspeptin, α-MSH, Melanocortins, Mc4r, Reproduction

Kisspeptin and RFRP-3 differentially regulate food intake and metabolic neuropeptides in the female desert jerboa

Jerboas are wild rodents exhibiting exceptional adaptation to their desert environment. Under harsh autumn conditions, they shut down reproduction, increase body weight and hibernate, while during spring they become sexually active even under negative energy-balance. We recently reported that these rhythms are associated with synchronized changes in genes expressing reproductive (Kiss1, Rfrp) and metabolic (Npy and Pomc) peptides, raising the hypothesis of coordinated seasonal regulation of both functions. Here we analyzed whether kisspeptin and RFRP-3 regulate food-intake in parallel to their established reproductive functions. Intracerebroventricular administration of kisspeptin inhibited food intake by 1.5-fold in fasted, but not ad-libitum fed, female jerboas captured in spring, an effect associated with an increase in Pomc and decrease in Rfrp mRNA levels. By contrast, intracerebroventricular injection of RFRP-3 induced a 4-fold increase in food-intake in ad-libitum female jerboas, together with a decrease in Pomc and increase in Npy mRNA levels. This orexigenic effect of RFRP-3 was observed in both spring and autumn, whereas kisspeptin's anorexigenic effect was only observed in spring. Altogether, this study reports opposite metabolic effects of kisspeptin and RFRP-3 in the female jerboa and strengthens our hypothesis of a coordinated, season-dependent, regulation of reproductive activity and food intake through interactions of these hypothalamic peptides.

Coordinated seasonal regulation of metabolic and reproductive hypothalamic peptides in the desert jerboa

Jerboa (Jaculus orientalis) is a semi-desert rodent displaying strong seasonal variations in biological functions in order to survive harsh conditions. When environmental conditions become unfavorable in early autumn, it shuts down its reproductive axis, increases its body weight, and finally hibernates. In spring, the jerboa displays opposite regulations, with a reactivation of reproduction and reduction in body weight. This study investigated how genes coding for different hypothalamic peptides involved in the central control of reproduction (Rfrp and Kiss1) and energy homeostasis (Pomc, Npy, and Somatostatin) are regulated according to seasons in male jerboas captured in the wild in spring or autumn. Remarkably, a coordinated increase in the mRNA level of Rfrp in the dorso/ventromedial hypothalamus and Kiss1, Pomc, and Somatostatin in the arcuate nucleus was observed in jerboas captured in spring as compared to autumn animals. Only Npy gene expression in the arcuate nucleus displayed no significant variations between the two seasons. These variations appear in line with the jerboa's seasonal physiology, since the spring increase in Rfrp and Kiss1 expression might be related to sexual reactivation, while the spring increase in genes encoding anorexigenic peptides, POMC, and somatostatin may account for the reduced body weight reported at this time of the year. J. Comp. Neurol. 524:3717-3728, 2016. © 2016 Wiley Periodicals, Inc.

Distribution and seasonal variation in hypothalamic RF-amide peptides in a semi-desert rodent, the jerboa

The jerboa is a semi-desert rodent, in which reproductive activity depends on the seasons, being sexually active in the spring-summer. The present study aimed to determine whether the expression of two RF-amide peptides recently described to regulate gonadotrophin-releasing hormone neurone activity, kisspeptin (Kp) and RF-amide-related peptide (RFRP)-3, displays seasonal variation in jerboa. Kp and/or RFRP-3 immunoreactivity was investigated in the hypothalamus of jerboas captured in the field of the Middle Atlas mountain (Morocco), either in the spring or autumn. As in other rodents, the Kp-immunoreactive (-IR) neurones were found in the anteroventro-periventricular and arcuate nuclei. RFRP-3 neurones were noted within the dorso/ventromedial hypothalamus. A marked sexual dimorphism in the expression of Kp (but not RFRP-3) was observed. The number of Kp-IR neurones was nine-fold higher, and the density of Kp-IR fibres and terminal-like elements in the median eminence was two-fold higher in females than in males. Furthermore, a significant seasonal variation in peptide expression was obtained with an increase in both Kp- and RFRP-3-IR cell bodies in sexually active male jerboas captured in the spring compared to sexually inactive autumn animals. In the arcuate nucleus, the level of Kp-IR cells and fibres was significant higher during the sexually active period in the spring than during the autumnal sexual quiescence. Similarly, the number of RFRP-3-IR neurones in the ventro/dorsomedial hypothalamus was approximately three-fold higher in sexually active jerboa captured in the spring compared to sexually inactive autumn animals. Altogether, the present study reports the distribution of Kp and RFRP-3 neurones in the hypothalamus of a desert species and reveals a seasonal difference in their expression that correlates with sexual activity. These findings suggest that these two RF-amide peptides may act in concert to synchronise the gonadotrophic activity of jerboas with the seasons.