Progesterone receptor distribution in the human hypothalamus and its association with suicide

Abstract

The human hypothalamus modulates mental health by balancing interactions between hormonal fluctuations and stress responses. Stress-induced progesterone release activates progesterone receptors (PR) in the human brain and triggers alterations in neuropeptides/neurotransmitters. As recent epidemiological studies have associated peripheral progesterone levels with suicide risks in humans, we mapped PR distribution in the human hypothalamus in relation to age and sex and characterized its (co-) expression in specific cell types. The infundibular nucleus (INF) appeared to be the primary hypothalamic structure via which progesterone modulates stress-related neural circuitry. An elevation of the number of pro-opiomelanocortin⁺ (POMC, an endogenous opioid precursor) neurons in the INF, which was due to a high proportion of POMC⁺ neurons that co-expressed PR, was related to suicide in patients with mood disorders (MD). MD donors who died of legal euthanasia were for the first time enrolled in a postmortem study to investigate the molecular signatures related to fatal suicidal ideations. They had a higher proportion of PR co-expressing POMC⁺ neurons than MD patients who died naturally. This indicates that the onset of endogenous opioid activation in MD with suicide tendency may be progesterone-associated. Our findings may have implications for users of progesterone-enriched contraceptives who also have MD and suicidal tendencies.

Fig. 1

Progesterone receptor distribution in the human hypothalamus and adjacent regions. A Nuclear PR expression in the infundibular nucleus (INF). B Nuclear PR expression in cells of EL and SEL, and SVZ along lateral ventricle. C Cytoplasmic PR expression in the cuboidal and columnar epithelium of the choroid plexus. D Nuclear PR expression in the pars tuberalis (PT) of the pituitary. Scale bars: 100 μm. E Schematic illustration of PR mapping throughout the human hypothalamus. F Sex and age signature of PR-ir cells throughout human hypothalamus (N = 1). a Males (blue); b Females (red). Abbreviations: AC, anterior commissure; AN, accessory neurosecretory nucleus; BST/BNST, bed nucleus of the stria terminalis; Cg, chiasmatic gray; cm, corpus mamillare; CP, choroid plexus; cu, cuneate nucleus; DBB, nucleus of the diagonal band (of Broca); DMN, dorsomedial nucleus; EC, ependymal cell; EL, ependymal layer; FM, fasciculus mammillothalamicus; fx, fornix; INF, infundibular nucleus; GW, gestational weeks; NTL, lateral tuberal nucleus; ot, optic tract; PeVN, periventricular nucleus; ph, posterior hypothalamic nucleus; Pi, pituitary; pm, postero-medial nucleus; POA, preoptic area; PR, progesterone receptor; PVA, periventricular area; PVN, paraventricular nucleus; rc, retrochiasmatic nucleus; SCN, suprachiasmatic nucleus; SDN, sexually dimorphic (or intermediate) nucleus; SEL, subependymal layer; SON, supraoptic nucleus; su, subthalamic nucleus; SVZ, subventricular zone, TG, tuberal gray; TMN, tuberomammillary nucleus; un, unicate nucleus; VMN, ventromedial nucleus

Fig. 2

Characterization of progesterone receptor immunoreactive cells in the PVN and INF. A and B Absent co-localization of PR in astrocytes (GFAP) or microglia (iba1). C and D Co-localization of PR in neural progenitors (GFAP-δ and nestin). E a PVN in the human hypothalamus. b-h Absent expression of PR in CRH⁺, TRH⁺, OXT⁺, AVP⁺, SOM⁺, TH⁺ or DYN⁺ neurons in the PVN. i Co-localization of PR in KISS1⁺ neurons in the PVN. F a INF in the human hypothalamus. b-f PR expression in POMC⁺, NPY⁺, SOM⁺, KISS1⁺ and DYN⁺ neurons in the INF. g Absent co-localization of PR in CRH⁺ neurons in the INF. Scale bars: A and D, 50 μm; B and C, 20 μm; E, a-e 30 μm, f and g 15 μm; F, a and b 20 μm, c-e 30 μm. Abbreviations: AVP, arginine-vasopressin; CRH, corticotropin-releasing hormone; DYN, dynorphin; GFAP, glial fibrillary acidic protein; GFAP-δ, glial fibrillary acidic protein-delta; Iba1, ionized calcium binding adaptor molecule 1; KISS1, kisspeptin; NPY, neuropeptide Y; OXT, oxytocin; POMC, pro-opiomelanocortin; SOM, somatostatin; TH, tyrosine hydroxylase; TRH, thyrotropin-releasing hormone (for other abbreviations see legend Fig. 1)

Fig. 3

Increased numbers of PR/POMC⁺ neurons contribute considerably to the POMC⁺ neuronal increase in MDS. A POMC⁺ and PR/POMC⁺ neurons (red arrows) in the INF of a control subject and a patient with MD who died of suicide. Higher magnification of the areas framed in a, c, e and g are shown in b, d, f and h, respectively. B Analyses between CTR and MD subjects (two-group comparison), and their subsets (five-group comparison) on: total neurons and volume of POMC (a-d), PR/POMC (e-h), total neurons of sPOMC (i-j), proportion of PR/POMC neurons in POMC neurons (k-l). Note that patients with MD who died of suicides or legal euthanasia presented more PR/POMC⁺ neurons in the INF than patients who died naturally. Scale bars: a, c, e and g, 1 mm; b, d, f and h, 100 μm. Abbreviations: CE, control subjects who died of legal euthanasia; CN, control subjects who died of natural causes; CTR, control subjects; MD, mood disorders; MDE, subjects with mood disorders who died of legal euthanasia; MDN, subjects with mood disorders who died of natural causes; MDS, subjects with mood disorders who died of suicide; PR/POMC, neurons co-labeling progesterone receptor and pro-opiomelanocortin; sPOMC, pro-opiomelanocortin neurons that did not express progesterone receptor. Note: * indicates 0.01 ≤ P<0.05, ** indicates 0.001 ≤ P<0.01, *** indicates 0.0001 ≤ P<0.001, **** indicates 0.00001 ≤ P<0.0001, Global-P<0.05

Fig. 4

Reduction of total number of NPY⁺ neurons in the INF of MD is not associated with PR. A NPY⁺ and PR/NPY⁺ neurons (red arrows) in the INF of a control subject and an individual with MD. Higher magnification of the areas framed in a, c, e and g are shown in b, d, f and h, respectively. B Analyses between CTR and MD subjects, and their subsets on: total neurons and volume of NPY (a-d), PR/NPY (e-h), total neurons of sNPY (i-j) and the proportion of PR/NPY neurons in NPY neurons (k-l). Note the sharp drop of NPY expression in MDE compared to CE (b, j). Scale bars: a, c, e and g, 1 mm; b, d, f and h, 100 μm. Abbreviations: PR/NPY, neurons co-labeling progesterone receptor and neuropeptide Y; sNPY, neuropeptide Y neurons that did not express progesterone receptor. Note: * indicates 0.01 ≤ P<0.05, ** indicates 0.001 ≤ P<0.01, *** indicates 0.0001 ≤ P<0.001, **** indicates 0.00001 ≤ P<0.0001, Global-P<0.05