Abstract
Testosterone is often used to improve the physiological function. But increased testosterone levels affect blood lipids and cause inflammation and oxidative stress, which are risk factors for vascular diseases. This study aimed at investigating the effects of testosterone on cerebral vascular injury using an established intracranial aneurysm (IA) model. Sixteen-week-old female C57Bl/6 mice were subcutaneously infused with testosterone propionate (TP; 5 mg/kg day) or plain soybean oil (controls) for 6 weeks. After 2 weeks of treatment, mice were given angiotensin II-elastase for another 4 weeks. The results showed that TP significantly increased cell apoptosis and reactive oxygen species production in cerebral artery, together with increases in plasma tumor necrosis factor-α (TNF-α) levels and in urinary 8-isoprostane levels. Plasma assays showed that 2 weeks after TP or soybean oil administration, the high-density lipoprotein (HDL) level was higher in the TP group than in controls. In vitro studies showed that testosterone increased TNF-α and monocyte chemotactic protein-1 mRNA and protein expression levels in RAW 264.7 macrophages. In summary, by reducing the HDL level, TP aggravates cerebral artery injury by increasing cell apoptosis, inflammation, and oxidative stress.
1 Introduction
Sex hormones are usually administered as therapeutics in patients with gonadal dysfunction or in transgenders. The levels of sex hormones can affect the development of vascular diseases, such as abdominal aortic aneurysms (AAAs) and intracranial aneurysms (IAs) [1,2]. However, the nature of testosterone effects on vascular diseases is controversial. For example, several studies indicated that testosterone protects against atherosclerosis and cardiometabolic syndrome [3,4,5]. On the contrary, some studies hold the opposite view that testosterone and its derivatives exert toxic effects on the cardiovascular system [6,7]. Animal experiments confirmed the mixed side effects of testosterone. Male mice castration improved angiotensin (Ang) II-induced AAAs [8]. Inhibition or genetic deletion of the androgen receptor decreased the growth of AAAs [9]. Testosterone administration increased the abundance of Ang II type 1A receptor mRNA in abdominal aorta and intensified Ang II-induced atherosclerosis and increased the prevalence of AAAs in neonatal female mice, but not in neonatal male mice [10]. The results of these studies indicated that an elevated level of testosterone may represent a risk factor of vascular injury.
Testosterone exerts several physiological effects, i.e., it decreases high-density lipoprotein (HDL) and increases low-density lipoprotein (LDL) levels [11,12,13]. According to a widespread opinion, a decrease in HDL and an increase in LDL levels contribute to vascular diseases through the activation of inflammatory cells. Clinical studies found that blood lipid content impacted on the formation and rupture of IAs [14,15]. High doses of testosterone could also cause inflammation and oxidative stress [16,17]. Both factors entail a high risk of IA development. It has been proved that many inflammatory cytokines such as interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), and IL-6 associate with IA rupture [18]. Moreover, it is widely recognized that oxidative stress helps promote cerebrovascular diseases by intensifying inflammation, worsening endothelial dysfunction, and inducing cell apoptosis, thereby causing vessel wall remodeling and degradation and ultimately IA rupture [19,20]. However, more relevant research is needed to clarify the mechanisms by which testosterone might trigger the IA development [2].
This study aimed at investigating the effects of testosterone on the Ang II-elastase-induced cerebral vascular injury. We hypothesized that testosterone could advance vascular injury and inflammation by affecting blood lipid levels. The in vivo part of our study assessed the brain vascular injury, inflammatory factors, oxidative stress, and plasma lipids. To better understand the underlying mechanisms, in vitro cultured RAW 264.7 macrophages were treated with testosterone, and their TNF-α and monocyte chemotactic protein-1 (MCP-1) expression levels were measured.
2 Materials and methods
2.1 Animals
Mice were housed in a laminar flow cabinet with a half-day light and half-day dark cycle and fed on standard diet (1025; HFK, Beijing, China) and water. Mice were anesthetized using isoflurane (970-00026-00; RWD, Shenzhen, China).
Ethical approval: The research related to animal use has been complied with all the relevant national regulations and institutional policies for the care and use of animals and has been approved by the Animal Care and Use Committee of Ankang Central Hospital.
2.2 Animal model
To investigate testosterone effects on vascular injury, we used the previously described [21] Ang II-elastase mouse IA model. Sixteen-week-old female mice were divided into two groups. The treated group mice were subcutaneously infused for 6 weeks with testosterone propionate (TP; 5 mg/kg day; T101368; Aladin, Shanghai, China) dissolved in soybean oil. The control group mice were infused with plain soybean oil only. After 2 weeks of TP or plain soybean oil treatment, 18-week-old mice were administered Ang II (1,000 ng/kg/min) through an implanted osmotic mini-pump (1004, Alzet pump; Durect, Cupertino, USA) and injected with 17 mU elastase (E8210; Solarbio, Beijing, China) into the basal cistern on the right side.
2.3 Histology
At termination, mice were perfused with 4% paraformaldehyde (PFA). Next, sampled vascular tissues were fixed in 4% PFA for 24 h and then embedded in optimal cutting temperature (OCT) compound (4583; Sakura, Torrance, USA). OCT samples were sliced to 8 µm (CM1950; Leica, Wetzlar, Germany). Slides were stained using a terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) kit (FA201; Transgen Biotech, Shanghai, China) for the cell apoptosis assay. To assess reactive oxygen species (ROS), we used the dihydroethidium (DHE) kit (BB47051; Bestbio, Shanghai, China). Pictures were taken under a microscope system (Axiocam 503; Zeiss, Jena, Germany; X-Cite 120Q, Excelitas, Waltham, USA).
2.4 Plasma TNF-α
At termination, blood was drawn from the left ventricle. Plasma was isolated by spinning at 3,000 rpm for 10 min. TNF-α was measured via an enzyme-linked immunosorbent assay (ELISA) kit (SEKM-0034-96T; Solarbio, Beijing, China) according to the manufacturer’s instructions.
2.5 Urine test
Before termination, a 24-h urine collection from metabolic cages was performed. To measure oxidative stress, we assayed 8-isoprostane (ELISA JL40844; Jianglai, Shanghai, China), a biomarker of oxidative stress. Creatinine was assayed as the reference compound (ELISA JL20489; Jianglai, Shanghai, China). The assays were performed following the instructions provided by the manufacturer. OD values were measured at 450 nm in a microplate reader (Epoch, BioTek, Winooski, USA).
2.6 Plasma lipids measurement
After 2 weeks of TP or plain soybean oil treatment, mice were sacrificed, and blood samples were drawn from their left ventricles. Plasma samples were collected after centrifugation and stored at −80°C. Plasma HDL, LDL, and triglycerides were measured by HDL (ml037767), LDL (ml063218), and triglycerides (ml063270) ELISA kits, respectively, that were bought from MLBio (Shanghai, China).
2.7 Cell culture
The RAW 264.7 murine macrophage cell line (SCC-211800; Solarbio, Beijing, China) was grown in high glucose Dulbecco’s Modified Eagle Medium (Hyclone, Logan, USA) supplemented with 10% FBS (13011-8611; Sijiqing, Hangzhou, China) and 1% penicillin–streptomycin. Cells were kept at 37°C in air with 5% v/v CO2 and subcultured every 48–72 h. Fifty thousand cells were seeded into each well of 6-well plates for 12 h and then incubated in serum-free medium for 24 h. After the addition of testosterone (10−7 mol/L; Aladdin, Shanghai, China), the cells were cultured for another 24 h to assess the hormone effects on macrophages. To remove cell debris, cell-conditioned media were centrifuged at 2,500 × g for 5 min and the supernatants were stored for further use. TNF-α and MCP-1 protein expression levels were measured by ELISA (SEKM-0108-96; Solarbio, Beijing, China). Cultured cells were collected to assess mRNA expression.
2.8 qRT-PCR
Total RNA was isolated using TRIzol (9109; Takara, Kusatsu, Japan). The cDNA was prepared by PrimeScript RT reagent Kit (RR047A; Takara, Kusatsu, Japan). qPCR was performed on an ABI-7300 apparatus (ABI, Foster, USA) using SYBR Green (B21203; Bimake, Shanghai, China). All steps were performed according to the manufacturer’s instructions. Primers: Tnf-α, forward, 5′-ACGTCGTAGCAAACCACCAA-3′, reverse, 5′-GCAGCCTTGTCCCTTGAAGA-3′; Mcp-1, forward, 5′-CCAGCCTACTCATTGGGATCA-3′, reverse, 5′-CTTCTGGGCCTGCTGTTCA-3′; Gapdh, forward, 5′-AGGTCGGTGTGAACGGATTTG-3′, reverse, 5′-GGGGTCGTTGATGGCAACA-3′. Gapdh was the reference gene used.
2.9 Statistical analysis
Results were expressed as mean ± SD. Group mean differences were evaluated by Student’s t-test using GraphPad Prism 6 (San Diego, USA). A P value of <0.05 was considered statistically significant.
3 Results
3.1 TP aggravated Ang II-induced apoptosis and ROS production in a mouse IA model
To investigate the effects of testosterone on vascular cell apoptosis, the TUNEL assay was applied to cerebral blood vessel slides. Results showed that TP significantly increased cell apoptosis in cerebral blood vessels (Figure 1a and b). DHE staining showed that TP significantly increased ROS production in cerebral blood vessel sections (Figure 1a and c). It means that TP aggravated Ang II-induced cerebral vascular injury.
TP aggravated vascular lesions in a mouse IA model. (a) Representative pictures of a cerebrovascular wall stained with DHE and TUNEL separately. (b) TUNEL staining showed that TP increased cell apoptosis in the blood vessel (positive cells/slide; control, 10.67 ± 3.502 vs TP, 17.17 ± 6.113; n = 6). (c) DHE staining showed that TP increased ROS production in the blood vessel wall (lesion area %/slide; control, 3.573 ± 1.589 vs TP, 6.323 ± 1.631; n = 6). *P < 0.05. TP, testosterone propionate.
3.2 TP increased the plasma inflammatory marker TNF-α and the urinary oxidative stress marker 8-isoprostane
Ang II promotes inflammation and oxidative stress [22]. To confirm the effects of TP on inflammation and oxidative stress, the plasma TNF-α and urinary 8-isoprostane levels were measured. Compared to the control group, TP significantly increased the plasma TNF-α level (Figure 2a) and the urine 8-isoprostane/creatinine ratio (Figure 2b).
TP increased inflammation and oxidative stress. (a) Plasma TNF-α level (pg/mL; control, 66.85 ± 4.050 vs TP, 73.06 ± 5.468; n = 7). (b) Urinary 8-isoprostane/creatinine ratio (pg/mg; control, 1398 ± 137.7 vs TP, 1575 ± 198.2; n = 9). *P < 0.05. TP, testosterone propionate.
3.3 TP decreased HDL plasma levels in mice
To detect the effects of TP on the regulation of plasma lipid levels in mice, after 2 weeks of treatment with TP or plain soybean oil, the mice were sacrificed and blood samples were drawn from them. The results showed that TP significantly decreased HDL plasma levels in mice (Figure 3a) but did not change LDL and triglyceride levels (Figure 3b and c).
Plasma lipid levels after 2 weeks of TP or plain soybean oil (control) treatment. (a) TP significantly decreased plasma HDL level (μg/μL; control, 2.276 ± 0.2050 vs TP, 2.120 ± 0.2207; n = 19). (b and c) TP did not change the levels of plasma triglycerides (μg/μL; control, 5.991 ± 0.6016 vs TP, 6.132 ± 0.5458; n = 19) and LDL (μg/μL; control, 1.734 ± 0.2345 vs TP, 1.749 ± 0.1771; n = 19). *P < 0.05. TP, testosterone propionate.
3.4 TP increased TNF-α and MCP-1 mRNA and protein expression levels in RAW 264.7 macrophages
To investigate the pro-inflammatory effects of TP on macrophages, RAW 264.7 cells were treated with TP. qRT-PCR and ELISA results showed that TP significantly increased TNF-α and MCP-1 mRNA and protein expression levels, respectively (Figure 4a–d).
TP increased TNF-α and MCP-1 levels in RAW 264.7 macrophages. (a and b) The mRNA expression levels of TNF-α (ratio; control, 1.000 ± 0.1868 vs treatment, 1.666 ± 0.4675; n = 8) and MCP-1 (ratio; control, 1.000 ± 0.08452 vs treatment, 1.097 ± 0.09157; n = 8). (c and d) The protein levels of TNF-α (ratio; control, 1.000 ± 0.06251 vs treatment, 1.111 ± 0.09776; n = 8) and MCP-1 (ratio; control, 1.000 ± 0.06382 vs treatment, 1.068 ± 0.05251; n = 8). *P < 0.05. **P < 0.01.
4 Discussion
Our present results show for the first time in an IA mouse experimental model that TP reduced plasma HDL level and increased cell apoptosis, oxidative stress, and inflammation, resulting in cerebral vascular injury.
Testosterone-induced vascular injury may be divided into several stages. At the early stage of the experiment, after 2 weeks of TP or plain soybean oil treatment, we isolated the blood before the Ang II-elastase infusion and analyzed the plasma lipids. It showed that TP decreased the HDL levels. In general, HDL is a key factor regulating vascular inflammation and macrophage infiltration. High levels of HDL can reduce macrophage infiltration and even remove infiltrated macrophages or push them toward the anti-inflammatory (M2) subtype [23]. Macrophages are the main source of oxidative stress products. Altered levels of both lipids and ROS are important causes of vascular injury. Later IA experiments in this study also confirmed this result. TP increased plasma TNF-α and urinary 8-isoprostane levels. To clarify whether testosterone directly affects the role of macrophages in vascular injury, we performed in vitro experiments to verify it. Consistent with our hypothesis, TP directly promoted an increased expression of the inflammatory factors TNF-α and MCP-1 in RAW 264.7 cells. These inflammatory factors can recruit additional macrophages, which may be the cause of increasing vascular inflammation intensity. Besides, macrophages can also degrade the vascular extracellular matrix (VECM) by secreting proteases, thus promoting vascular wall remodeling. Under the joint action of these factors, TP advanced the development of cerebral vascular injury.
Several previous studies have shown results that are consistent with ours but in different tissues. In AAA studies, testosterone treatment promoted aneurysm growth [24]. Inhibition or genetic deletion of the androgen receptor attenuated the AAA development, which was related to the decreased pro-inflammatory factors IL-1α, IL-6, and IL-17 [9]. These results may be explained by the fact that testosterone increased collagen deposition but decreased elastin deposition [1,25,26], leading to vascular wall remodeling. Altogether, the aforementioned results and those of this study show that high testosterone levels increase the probability of vascular injury.
In TP-aggravated cerebral vascular injury, the decrease in HDL acts as a key regulator. A clinical study showed that testosterone level is the major reason for the male–female differences in serum HDL-cholesterol levels, whereas the serum levels of total cholesterol, LDL, triglycerides, apolipoprotein B, and apolipoprotein A2 were not affected by testosterone [13]. A cohort study found that a lower HDL level in females was the only risk factor of a big size IA [14]. Another clinical study also remarkably indicated that lipid-lowering drugs and a higher HDL level are inversely associated with IA rupture, whereas LDL and total cholesterol levels were not significant under the same respect [15]. These studies further increased our knowledge of the HDL protective mechanisms against vascular injury. Therefore, we believe that the testosterone administration–aggravated brain vascular injury in our female IA model is linked to the concurrently reduced HDL levels.
Some studies held the opposite view. They suggested that testosterone exerts neuroprotective and anti-inflammatory effects in the central nervous system [2,27,28]. Also, testosterone inhibited vasospasms in subarachnoid hemorrhage model rabbits [29]. These findings may be related to the dosage and users. Most clinical studies of sex hormones are concerned with people with endocrine disorders or testosterone deficiency, especially middle-aged and older men [30,31]. Administered testosterone restores sex hormones to normal levels. There is no doubt that normal hormone levels are good for the body. But any overdose may entail potential risks such as increases in inflammation, oxidative stress, and cardiovascular disease. A study of renal ischemia–reperfusion (I/R)–induced acute kidney injury (AKI) in male rats showed that low-dose (20 µg/kg) testosterone protected against I/R AKI by reducing renal T-cell infiltration and shifting the balance of pro-inflammatory/anti-inflammatory cytokine production [32]. Higher dose of testosterone (100 µg/kg) not only did not mitigate renal injury but also increased both IL-10 and TNF-α levels. A recent review shared our point of view [7]. They pointed out that the number of testosterone prescriptions in the United States has increased in recent years. More than one-sixth of the men taking such therapy did not reach the baseline value of serum testosterone, suggesting that the patients may unnecessarily have taken testosterone. A later analysis found that testosterone may increase the cardiovascular risk. In consequence, we believe that the dose of testosterone to be administered is crucial to properly regulate physiological functions.
In summary, the administration of TP aggravates cerebral vascular injury by increasing the oxidative stress and inflammation by decreasing the HDL level in an Ang II-elastase-induced IA mice model. These results further inform us about the vascular protection mechanisms of sex hormones and their receptors, especially those related to the regulation of macrophage function and plasma HDL levels. They also supply a theoretical basis for the clinical application. It is necessary to measure the serum testosterone value before prescribing it to people who need testosterone therapy to avoid the risks of an overtreatment. Alternatively, testosterone supplements should be contraindicated in patients with a diagnosis of IA.
Acknowledgments
The authors thank Professor Song Jinning (First Affiliated Hospital of Xi’an Jiaotong University) for his suggestions.
Author contributions: Design: T.J.; Animal operation: T.J.; Cell culture: T.J. and L.W.; Experiments: T.J. and L.W.; Data analysis and writing: T.J.; D.L., T.Y., and Y.Z. supervised the study and edited the manuscript. All authors discussed the manuscript.
Conflict of interest: The authors state no conflict of interest.
Data availability statement: The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
References
[1] Villard C, Hultgren R. Abdominal aortic aneurysm: Sex differences. Maturitas. 2018;109:63–9.10.1016/j.maturitas.2017.12.012Search in Google Scholar PubMed
[2] Barrow JW, Turan N, Wangmo P, Roy AK, Pradilla G. The role of inflammation and potential use of sex steroids in intracranial aneurysms and subarachnoid hemorrhage. Surgical Neurol Int. 2018;9:150.10.4103/sni.sni_88_18Search in Google Scholar PubMed PubMed Central
[3] Rezanezhad B, Borgquist R, Willenheimer R, Elzanaty S. The association between serum testosterone and risk factors for atherosclerosis. Curr Urol. 2019;13(2):101–6.10.1159/000499285Search in Google Scholar PubMed PubMed Central
[4] Aherrahrou R, Kulle AE, Alenina N, Werner R, Vens-Cappell S, Bader M, et al. CYP17A1 deficient XY mice display susceptibility to atherosclerosis, altered lipidomic profile and atypical sex development. Sci Rep. 2020;10(1):8792.10.1038/s41598-020-65601-0Search in Google Scholar PubMed PubMed Central
[5] Kirlangic OF, Yilmaz-Oral D, Kaya-Sezginer E, Toktanis G, Tezgelen AS, Sen E, et al. The effects of androgens on cardiometabolic syndrome: Current therapeutic concepts. Sex Med. 2020;8(2):132–55.10.1016/j.esxm.2020.02.006Search in Google Scholar PubMed PubMed Central
[6] Liu JD, Wu YQ. Anabolic-androgenic steroids and cardiovascular risk. Chin Med J. 2019;132(18):2229–36.10.1097/CM9.0000000000000407Search in Google Scholar PubMed PubMed Central
[7] Gagliano-Jucá T, Basaria S. Trials of testosterone replacement reporting cardiovascular adverse events. Asian J Androl. 2018;20(2):131–7.10.4103/aja.aja_28_17Search in Google Scholar PubMed PubMed Central
[8] Zhang X, Thatcher S, Wu C, Daugherty A, Cassis LA. Castration of male mice prevents the progression of established angiotensin II-induced abdominal aortic aneurysms. J Vasc Surg. 2015;61(3):767–76.10.1016/j.jvs.2013.11.004Search in Google Scholar PubMed PubMed Central
[9] Davis JP, Salmon M, Pope NH, Lu G, Su G, Meher A, et al. Pharmacologic blockade and genetic deletion of androgen receptor attenuates aortic aneurysm formation. J Vasc Surg. 2016;63(6):1602–12.10.1016/j.jvs.2015.11.038Search in Google Scholar PubMed PubMed Central
[10] Zhang X, Thatcher SE, Rateri DL, Bruemmer D, Charnigo R, Daugherty A, et al. Transient exposure of neonatal female mice to testosterone abrogates the sexual dimorphism of abdominal aortic aneurysms. Circulation Res. 2012;110(11):e73–85.10.1161/CIRCRESAHA.111.253880Search in Google Scholar PubMed PubMed Central
[11] Velho I, Fighera TM, Ziegelmann PK, Spritzer PM. Effects of testosterone therapy on BMI, blood pressure, and laboratory profile of transgender men: A systematic review. Andrology. 2017;5(5):881–8.10.1111/andr.12382Search in Google Scholar PubMed
[12] Irwig MS. Testosterone therapy for transgender men. Lancet Diabetes Endocrinol. 2017;5(4):301–11.10.1016/S2213-8587(16)00036-XSearch in Google Scholar PubMed
[13] Asscheman H, Gooren LJ, Megens JA, Nauta J, Kloosterboer HJ, Eikelboom F. Serum testosterone level is the major determinant of the male-female differences in serum levels of high-density lipoprotein (HDL) cholesterol and HDL2 cholesterol. Metabolism. 1994;43(8):935–9.10.1016/0026-0495(94)90170-8Search in Google Scholar PubMed
[14] Huang Q, Shang-Guan HC, Wu SY, Yao PS, Sun Y, Zeng YL, et al. High-density lipoprotein is associated with progression of intracranial aneurysms. World Neurosurg. 2018;120:e234–e40.10.1016/j.wneu.2018.08.037Search in Google Scholar PubMed
[15] Can A, Castro VM, Dligach D, Finan S, Yu S, Gainer V, et al. Lipid-lowering agents and high HDL (High-density lipoprotein) are inversely associated with intracranial aneurysm rupture. Stroke. 2018;49(5):1148–54.10.1161/STROKEAHA.117.019972Search in Google Scholar PubMed PubMed Central
[16] Quintero-Garcia M, Delgado-Gonzalez E, Sanchez-Tusie A, Vazquez M, Aceves C, Anguiano B. Iodine prevents the increase of testosterone-induced oxidative stress in a model of rat prostatic hyperplasia. Free Radic Biol Med. 2018;115:298–308.10.1016/j.freeradbiomed.2017.12.014Search in Google Scholar PubMed
[17] Holmes S, Singh M, Su C, Cunningham RL. Effects of oxidative stress and testosterone on pro-inflammatory signaling in a female rat dopaminergic neuronal cell line. Endocrinology. 2016;157(7):2824–35.10.1210/en.2015-1738Search in Google Scholar PubMed PubMed Central
[18] Kao HW, Lee KW, Kuo CL, Huang CS, Tseng WM, Liu CS, et al. Interleukin-6 as a prognostic biomarker in ruptured intracranial aneurysms. PLoS One. 2015;10(7):e0132115.10.1371/journal.pone.0132115Search in Google Scholar PubMed PubMed Central
[19] Starke RM, Chalouhi N, Ali MS, Jabbour PM, Tjoumakaris SI, Gonzalez LF, et al. The role of oxidative stress in cerebral aneurysm formation and rupture. Curr Neurovasc Res. 2013;10(3):247–55.10.2174/15672026113109990003Search in Google Scholar PubMed PubMed Central
[20] Starke RM, Thompson JW, Ali MS, Pascale CL, Martinez Lege A, Ding D, et al. Cigarette smoke initiates oxidative stress-induced cellular phenotypic modulation leading to cerebral aneurysm pathogenesis. Arterioscler Thromb Vasc Biol. 2018;38(3):610–21.10.1161/ATVBAHA.117.310478Search in Google Scholar PubMed PubMed Central
[21] Kanematsu Y, Kanematsu M, Kurihara C, Tada Y, Tsou TL, van Rooijen N, et al. Critical roles of macrophages in the formation of intracranial aneurysm. Stroke. 2011;42(1):173–8.10.1161/STROKEAHA.110.590976Search in Google Scholar PubMed PubMed Central
[22] Yang G, Istas G, Hoges S, Yakoub M, Hendgen-Cotta U, Rassaf T, et al. Angiotensin-(1–7)-induced mas receptor activation attenuates atherosclerosis through a nitric oxide-dependent mechanism in apolipoproteinE-KO mice. Pflug Arch. 2018;470(4):661–7.10.1007/s00424-018-2108-1Search in Google Scholar PubMed
[23] Feig JE, Rong JX, Shamir R, Sanson M, Vengrenyuk Y, Liu J, et al. HDL promotes rapid atherosclerosis regression in mice and alters inflammatory properties of plaque monocyte-derived cells. Proc Natl Acad Sci U S A. 2011;108(17):7166–71.10.1073/pnas.1016086108Search in Google Scholar PubMed PubMed Central
[24] Cho BS, Woodrum DT, Roelofs KJ, Stanley JC, Henke PK, Upchurch GR. Differential regulation of aortic growth in male and female rodents is associated with AAA development. J Surg Res. 2009;155(2):330–8.10.1016/j.jss.2008.07.027Search in Google Scholar PubMed PubMed Central
[25] Fischer GM, Swain ML. Influence of contraceptive and other sex steroids on aortic collagen and elastin. Exp Mol Pathol. 1980;33(1):15–24.10.1016/0014-4800(80)90003-9Search in Google Scholar PubMed
[26] Natoli AK, Medley TL, Ahimastos AA, Drew BG, Thearle DJ, Dilley RJ, et al. Sex steroids modulate human aortic smooth muscle cell matrix protein deposition and matrix metalloproteinase expression. Hypertension. 2005;46(5):1129–34.10.1161/01.HYP.0000187016.06549.96Search in Google Scholar PubMed
[27] Matsumoto A. Hormonally induced neuronal plasticity in the adult motoneurons. Brain Res Bull. 1997;44(4):539–47.10.1016/S0361-9230(97)00240-2Search in Google Scholar
[28] Pike CJ. Testosterone attenuates beta-amyloid toxicity in cultured hippocampal neurons. Brain Res. 2001;919(1):160–5.10.1016/S0006-8993(01)03024-4Search in Google Scholar
[29] Gurer B, Turkoglu E, Kertmen H, Karavelioglu E, Arikok AT, Sekerci Z. Attenuation of cerebral vasospasm and secondary injury by testosterone following experimental subarachnoid hemorrhage in rabbit. Acta Neurochir (Wien). 2014;156(11):2111–20. Discussion 20.10.1007/s00701-014-2211-9Search in Google Scholar PubMed
[30] Jones TH, Kelly DM. Randomized controlled trials – mechanistic studies of testosterone and the cardiovascular system. Asian J Androl. 2018;20(2):120–30.10.4103/aja.aja_6_18Search in Google Scholar PubMed PubMed Central
[31] Traustadóttir T, Harman SM, Tsitouras P, Pencina KM, Li Z, Travison TG, et al. Long-term testosterone supplementation in older men attenuates age-related decline in aerobic capacity. J Clin Endocrinol Metab. 2018;103(8):2861–9.10.1210/jc.2017-01902Search in Google Scholar PubMed PubMed Central
[32] Patil CN, Wallace K, LaMarca BD, Moulana M, Lopez-Ruiz A, Soljancic A, et al. Low-dose testosterone protects against renal ischemia-reperfusion injury by increasing renal IL-10-to-TNF-alpha ratio and attenuating T-cell infiltration. Am J Physiol Ren Physiol. 2016;311(2):F395–403.10.1152/ajprenal.00454.2015Search in Google Scholar PubMed PubMed Central
© 2020 Tao Jin et al., published by De Gruyter
This work is licensed under the Creative Commons Attribution 4.0 International License.
