Androgen Flashcards
-androgen to estrogen conversion by
aromatase
do hormones act directly on microglia?
could be direct or indirect (modulating microenvironments that impart sex difference din microglia identity and function)
Whats condition girls have with excess androgen?
congenital adrenal hyperplasia (cortical synthesis pathway mutation)
When do testes and ovary develop? What week?
6-12
When does T peak in males human?
Week 12-18
How much higher is male T in utero at 34-41 weeks than F?
10 times
When is second peak of T after birth?
Around 3 months
When does sexual differentiation of the genitals happen and then the brain?
G: 2 months of pregnancy
B: Second semester
What’s a brain region organized by estradiol ?
Preoptic area - a brain region involved in many areas including copulatory and maternal behaviors
In early development, what determines whether an animal will develop testes or ovaries?
Genes on the sex chromsome (SRY gene on Y chromosome) -> testes produce androgen and absence of SRY gene -> ovarian devlopment
What does estrogen do in the rat brain?
1) masculinzation
2) defiminization
Why use that does of flutamide?
Flutamide was administered at a dose of 50 mg/kg bodyweight and prepared on the same day as the injection. This dose was selected as it is well-established in impairing male reproductive development and preventing masculinization of anogenital distance (AGD)
hwy not enzalutamide?
this increased potency could also have an effect on non-reproductive tissues where androgen signaling is involved, such as the musculoskeletal system (possibly affecting muscle mass)
why did you use flutamide?? is this a specific androgen effect
you’re right in the sense that there are potentially confounding effects of estrogen since T can be converted into E by aromatase - follow up studies could perhaps also administer the addition of an inhibitor of the enzyme
we actually hypothesize that estradiol could have been responsible for that increase in mature OLs we saw in the flutamide group and that’s bc with flutamide tx you generally have an increase in T, so more T converted into estradiol, E seen to prolong cell cylce of OL precurosor - so overall you have a higher pool at the end
other studies have made use of castration then administration of DHT since it’s not able to be aromatized
we also don’t know for sure if its T or DHT having any effects - also crosstalk with estrogne signalling?
where is AR located?
x chromosome, c domain
where does brain masculinization occur in rats?
ER eg preoptic area of the hypothalamus estrogen to neonatal female rats can masculnize their brains
why use flutamide instead of enzalutamide?
a broad inhibition of androgen signaling, including both genomic and non-genomic effects. While enzalutamide specifically prevents androgen receptor (AR) nuclear translocation and is highly potent in targeting the genomic actions of AR
minimizes interference with other steroid hormone pathways since it’s non steroidal, reduces the risk of systemic side effects
Well-Characterized in Preclinical Models
Less Potent but Sufficient for General Blockade -
widely used in animal studies, flutamide has minimal CNS effects than enzalutamide, multiple steps of AR signalling - would have broader effects so we were
how is androgen impacting innate immune cells?
sex hormones directly influence both the development and function of cells of both the innate
androgens impact PMN maturation and function
including cell proliferation, cytokine secretion, and toll-like receptor expression.
e.g orchiectomized mice were reduced to the levels found in female mice, PMN from orchiectomized mice also showed a trend toward decreased cytotoxicity and the number of mature, segmented PMN compared to those from control male mice, less phagocytosis, ROS. These results were able to be reversed with testosterone replacement, clearly highlighting that abnormal phenotypic changes occur in PMNs that express the AR after orchiectomy.
In a study by Chuang et al., AR-knockout male mice were neutropenic and more susceptible to acute bacterial infection.41 This highlights that the AR is important for the development of PMN precursor cells and that it impacts their proliferative activity
Across the aforementioned studies, it is evident that the AR and/or androgens stimulate the production of PMN. Mechanistically, this could be explained through AR enhancing granulocyte colony-stimulating factor signaling as found in a study by Chuang et al.41 This mechanism works through the activation of extracellular signal-regulated kinase 1/2 and through sustaining signal transducer and activator of transcription (STAT)3 activity.39 Many knockout mice studies have shown that when STAT3 activity is maintained, the result is a hyperproduction of neutrophils.45, 46 In sum, the reason why males are at a higher risk of developing sepsis and other innate immune driven-conditions could in part be explained by a skewed activation of PMN by testosterone, which contributes to a weaker ability to clear the infection than female, or, on the other hand, due to a testosterone-induced cytokine storm from innate immune cells, or both.
describe production of androgen
Testosterone synthesis is regulated by a negative feedback loop within the hypothalamic–pituitary–gonadal axis.13 The hypothalamus secretes gonadotropin-releasing hormone (GnRH) that stimulates the secretion of luteinizing hormone (LH) and follicle-stimulating hormone.13, 14 These gonadotropic hormones travel via the blood and act on their respective receptors in the gonads. LH acts directly on Leydig cells in the testis to produce testosterone.15 When circulating levels of testosterone rise, this signals the hypothalamic–pituitary complex to reduce gonadotropin secretion.
Conversion of cholesterol into testosterone primarily occurs in the Leydig cells of the testis
give example illness/disease that happens more in men bc of androgen
impaired wound healing (androgne acts on skin macrophage)
prevalence of neonatal sepsis is higher in males compared to female, inflammatory storm observed in septic shock and complications of meningitis may be under the influence of sex hormones in males
can sexual dimorphism be explained by genes?
can in part be explained by genetic differences between males and females, specifically the imbalance in the expression of genes encoded on the X and Y chromosomes.
how do they impact innate immune cells what’s the mechanism?
impact functioning of immune cells: orchiectomized mice (lacking in T) exhibit reduced PMN cytotoxicity, phagocytosis, and ROS production. Testosterone replacement restores these functions, underscoring the direct role of androgens in PMN activity
impact cytokine secretion and TLR expression
impact proliferation/ development of immune cells e.g AR signaling enhances granulocyte colony-stimulating factor (GCSF) pathways via ERK1/2 activation and sustained STAT3 signaling, which are crucial for PMN development and function. . AR ko mice are neutropenic - with fewer mature, segmented PMNs
mechanistically - AR signaling can modulate NF-κB activity either directly or through crosstalk with other signaling pathways, impacting cytokine secretion (e.g., TNF-α, IL-6) and the inflammatory response.
Dysregulated NF-κB activity under androgen influence might contribute to cytokine storms or impaired resolution of inflammation, exacerbating conditions like sepsis
what is nfkb
NF-κB is a transcription factor that regulates the expression of genes involved in immune and inflammatory responses. It is activated in response to various stimuli, such as cytokines, stress, or infection. Once activated, NF-κB translocates to the nucleus and promotes the transcription of target genes, including those involved in cytokine production, cell survival, and immune cell recruitment
what is gcsf
G-CSF is a cytokine that primarily stimulates the proliferation, differentiation, and activation of neutrophil precursors in the bone marrow. It is crucial for neutrophil production and function.
androgen and nfkb
Cross-Modulation and Transcriptional Interference: AR and NFκB can cross-modulate, leading to transcriptional interference and impacting downstream inflammatory gene expression.
Physical Interaction: The AR physically interacts with NFκB, influencing cytokine production and inflammatory responses. This interplay could contribute to a skewed inflammatory profile in males with high androgen levels.
AR and NF-κB physically interact at the protein level:
Direct Binding: AR can bind to NF-κB subunits (e.g., p65/RelA) to either block or enhance NF-κB’s ability to bind DNA and activate inflammatory genes.
Post-Translational Modifications: AR signaling might alter the phosphorylation or ubiquitination state of NF-κB, affecting its stability and activity.
- Transcriptional Interference
Both AR and NF-κB are transcription factors that compete for co-activators, which are necessary for gene transcription. This competition can lead to:
Gene Suppression: AR activation can reduce the ability of NF-κB to transcribe pro-inflammatory genes by sequestering co-activators like p300/CBP.
Gene Activation: In certain contexts, AR and NF-κB may synergize to promote the expression of genes involved in inflammation and cell proliferation.
when is the AR programming window
G15-19
what is the purpose of male surge of T?
becoming male : activation of Sry gene –> differentiation testis –> production of T by leydig cells–>
differentiation of internal (epididymis, vas deferens, seminal vesicles, prostate) and external genitalia (external)
when does Testis appear?
G13
7 weeks human (starstt proudcing T)
what does the neonatal surge do in rats and humnas?
neonatal testosterone surge is responsible for establishing brain sexual dimorphisms that underpin sexually dimorphic physiology and behaviour
humans less striaghtforward
Evidence suggests that the majority of brain sexual differentiation in primates is established by exposure to androgens prenatally rather than neonatally,
what is the surge of T driven by?
fetla hypothlalmus produced GnRH –> pituitary –> LH/FSH –> LH acts on leydig cells of testis to produce
T
hCG produced by the placenta mimics LH and stimulates leydig cells to produce test - first trimester before pituitary becomes fully functional
T peak in humans
15-18 weeks
T peak in rats
G18-22
what controls the surge?
presence of SRY gene on y chromosome intiaties t development –> t production
placental influence: hcg - early T, produced by the placenta and acts smiliarly to LH - responsible for leydig cells in testes to produce T
negative feebdack
explain brain masculinization
humans mostly prenatal (not much evidence for estradiol effect)
rats mostly postnatal (mediated by estradiol)
T converted into estradiol - changes in gene expression & structural developme in hypothalamus, amygdala, preoptic areas –> male typical behaviors - influences structural and functional brain differences
aromatization hypothesis cannot account for all sex differences in brain morphology and behavior.
For example, alpha-fetoprotein binds estrogen and prevents it from entering and masculinizing the brain in rodents (Bakker et al., 2006; Puts et al., 2006), but has very low affinity for estrogen in primates (Swartz and Soloff, 1974). If the aromatization hypothesis were generally true in primates, it would seem that ovarian estrogens would cross the blood-brain barrier and masculinize the female brain.
human: 5alpha-dihydrotestosterone, produced very similar masculinizing and defeminizing effects in monkeys
diff between male and female brain
Overall sex differences have been found in total brain size, with the male brain being on average 11% larger than the female brain. At the regional level, robust sex differences have been found in the amygdala, hippocampus, insula and parts of the frontal cortex, among many other regions.
effect of flutamide ?
Cryptorchidism and absence of the prostate gland and seminal vesicles were found in males at doses
Hypospadias was noted in all dose groups and vaginal pouches at doses of ≥10 mg/kg
Male offspring exposed to flutamide in utero showed impairments of sexual behavior as adults in a dose-related manner. Number and frequency of mounts with intromissions was markedly decreased in all treated groups as compared to control
no mounting with intromission or ejaculation was observed. These changes in sexual behavior were closely associated with abnormalities of the external genitalia
Histological examination of the reproductive organs revealed degeneration of the seminiferous tubules, hypospermatogenesis, and hypoplasia and inflammation of the seminal vesicles and prostate.
eductions in weight of testes and prostate, percentage of normal spermatozoa, spermatozoa concentration, testicular sperm production, and testosterone level. Normal females mated with treated males presented more pre-implantation losses, reduced implantation rates, and consequently reduced offspring size
can inflammation impact aromatase expression?
yes in obesity aromatse is increased
In obesity, chronic inflammation leads to increased aromatase activity, particularly in adipose tissue, which results in elevated estrogen production. This can have significant effects on hormonal balance,
is the HPG axis primarliy responsible for surge?
towards the end yes, but the begining it is hcg (human chorionic gonadotropin) bc HPG still underdevleoped
when is androgen surge in humans?
8-12 wk (first trimester)
when is androgen surge in rats?
G16-18 (3rd trimester)
could androgen impact 5 a reductase?
yes, you have il1b being able to increase these levels more conversion into DHT
inflammation can affect HPG - this reuglates T production, so inflammation could increase corticosteroid levels impacting testosterone production
diff in structure between T and flut
T classic steroid - 4 major ring sturcture - flutamide has an aromatic ring and amide group, so F binds preventing activation
why use F over enzalutamide?
F well characterized in rodent models, it is less potent and has a shorter half like than for examples enzalutamide. we are targeting a more broad, moderate range blockade since F prevents competes with androgens for binding. enzalutamide prevents translocatin of the AR to the nucleus - > so it will have other off target effects, greater systemic effects
F used for prostate cancer?
