Interestingly, it was found that serum testosterone levels among hypogonadal men were negatively correlated with CpG (oligodeoxynucleotides)-stimulated expression of CD107b by CD16+ DCs. Another study was performed in men with hypogonadism, also known as testosterone deficiency, where the authors compared the distribution and functional status of peripheral blood (PB) monocytes and DCs (CD16+) among other cell types compared to male control subjects. These results point out that sex differences observed in the progression of HIV-1 may be due to stronger immune responses in women, which present higher activation of pDCs induced by TLR compared to men at a given viral load (77). In addition, ER expression was found in hepatic DCs, suggesting altogether an influence of sex hormones on DC function in mice (76). Asthmatic women present more M2 macrophages than asthmatic men, therefore androgens were used as an experimental asthma treatment. TLR4 is a transmembrane receptor that when activated leads to intracellular NF-κB signaling pathway induction and inflammatory cytokine production, promoting the activation of the innate immune system (69). Epidemiological studies identified male gender as an independent risk factor for the development of severe infection compared with females. Macrophages are recognized to play essential roles in sepsis and influence both inflammatory responses and immune homeostasis. In line with this, a complex network of cytokine and immune cell interactions is present during sepsis in humans leading to high mortality due to organ dysfunction or failure. Notably, this effect was reverted when the mice were treated with exogenous testosterone (66). They represent specialized cells involved in the detection, phagocytosis and destruction of bacteria and other foreign and harmful microorganisms. With the recent emergence of immunotherapy for the treatment of many solid tumors, the use of checkpoint therapies for castration-resistant metastatic prostate has become increasingly intriguing. A lack of AR signaling in the bone marrow prevents the maturation of neutrophils and impedes homing to tumor-bearing lungs. Neutrophil-derived factors have been shown to have stimulatory effects on NK cells, including enhancement of cytotoxic activity, enhancement of survival, induction of CD69, and upregulation of CD11b57. Indeed, Agonaute2 (AGO2) complex pull-down followed by PD-L1 mRNA detection is consistent with this hypothesis (data not shown), suggesting that miRNAs might be involved in regulating PD-L1 protein expression in response to a high dose DHT treatment. Indeed, this increased PD-L1 expression persisted at least 36 h in the absence of DHT after 48 h treatment with a high dose DHT, likely impacting the NK cells killing as described earlier (Fig. 2C, D). To test whether PD-L1 might be mediating this effect to impact CRPC cell viability, we directly measured the expression of PD-L1 in response to a high dose DHT in EnzS1-C4-2 and EnzR1-C4-2 cells. We knocked down the expression of AR in EnzS1-C4-2 and EnzR1-C4-2 cells (Fig. 1D) by AR-shRNA followed by a high dose DHT treatment. Previous studies have demonstrated that testosterone has effects on various enzymatic pathways involved in fatty acid metabolism, glucose control, and energy utilization. High hepatocyte lipid droplet accumulation in the liver propagates liver injury and causes a storm of pro-inflammatory cytokines that can lead to steatosis and hepatocyte injury (Chin et al., 2020). Free cholesterol activates HSCs, and the addition of cholesterol to a high-fat or methionine/choline-deficient diet leads to the accumulation of free cholesterol in HSCs, which accelerates experimental liver fibrosis (Tomita et al., 2014). The same data patterns were obtained using NK activation markers of CD107a (Figure 4B). Flow cytometry analysis data demonstrated trNK (B) CD107a and (C) IL-6R percentages. Testosterone ameliorates liver injury by reducing NK IFN γ and improving liver trNK activity. The results of MTT assay showed that blocking PD-L1 with anti-PD-L1 antibody resulted in partial reverse of NK cells cytotoxicity (Fig. 2H). In addition, we directly incubated EnzS1-C4-2 and EnzR1-C4-2 cells with either 1 μg of PD-L1 rabbit polyclonal antibody (Abclonal, Woburn, MA) or rabbit IgG control antibody under high dose DHT. To determine whether PD-L1 plays an essential role in the inhibition of NK cells killing capacity, we suppressed PD-L1 in EnzS1-C4-2 and EnzR1-C4-2 cells and then treated with high dose DHT. H After treating EnzS1-C4-2 and EnzR1-C4-2 cells with 50 nM DHT for 48 h, PD-L1 neutralizing antibody or IgG control antibody, as well as NK92-MI cells, were added for 36 h, then MTT assay was performed to evaluate the NK cell cytotoxicity. E Full length AR was inhibited in EnzS1-C4-2 (left panel) and EnzR1-C4-2 (right panel) cells, cells were treated with 50 nM DHT for 48 h, then western blot was performed to test PD-L1 changes compared with scr group. This needs to be taken into account also in the context of androgen-mediated effects on immune cells (please see below). Therefore, local sex-hormone-mediated effects will be determined by the expression levels of either enzyme, as this will directly regulate the balance between androgen and estrogen production (13). A particular focus will be on cancer, highlighting the effect of androgens on immune surveillance, tumor biology and on the efficacy of anti-cancer therapies including emerging immune therapies. Some studies show that androgen deprivation therapy (ADT) can induce expansion of naïve T cells and increase T-cell responses. Targeting the immune system, particularly NK cells, may be a promising strategy for delaying liver injury. These beneficial effects were accompanied by a decrease in the expression of IL-6 receptors on liver-resident NK cells and an increase in NK cell activity. Moreover, our data showed a decrease in collagen and αSMA levels following testosterone treatment. However, the percentages reported in this study are extremely low, raising the question of functional significance.52 Recently, a systematic screen of commonly used drugs on isolated NK cells supported a direct effect of serotonin on NK cells. A flow cytometry-based study on Alzheimer’s patients suggests that NK cells may express serotonin receptors. The first connection between serotonin and NK cell function was found in the early 1990s, when Hellstrand et al. identified indirect effects of serotonin on NK cells through the regulation of monocytes by serotonin. Peripheral serotonin (5-hydroxytryptamine, 5-HT) is a derivative of tryptophan and is mainly produced by gut chromaffin cells.
