Hyperlipidemia impairs erectile function in rats by causing cavernosal fibrosis

MiRNA-100 ameliorates diabetes mellitus-induced erectile dysfunction by modulating autophagy, anti-inflammatory, and antifibrotic effects

BACKGROUND

Diabetes mellitus-induced erectile dysfunction (DMED) has become a common disease in adult men that can seriously reduce the quality of life of patients, and new therapies are urgently needed. miRNA-100 has many targets and can induce autophagy and reduce fibrosis by inhibiting the mTOR pathway and the TGF-β pathway. However, no research has been conducted with miR-100 in the field of DMED, and the specific mechanism of action is still unclear.

OBJECTIVES

To ascertain the effects of miR-100 on corpus cavernosum tissue of DMED rats and vascular endothelial cells in a high glucose environment and to elucidate the relevant mechanisms in autophagy, fibrosis and inflammation to find a new approach for the DMED therapy.

METHODS

Thirty rats were divided into three groups: the control group, the DMED group, and the DMED + miR-100 group. Using intraperitoneal injections of streptozotocin, all rats except the control group were modeled with diabetes mellitus, which was verified using the apomorphine (APO) test. For rats in the DMED + miR-100 group, rno-miR-100-5p agomir (50 nmol/kg, every 2 days, 6 times in total) was injected via the tail vein. After 13 weeks, the erectile function of each rat was assessed using cavernous manometry, and the corpus cavernosum tissue was harvested for subsequent experiments. For cellular experiments, human coronary microartery endothelial cells (HCMEC) were divided into four groups: the control group, the high-glucose (HG, 40 mM) group, the HG + mimic group, and the HG + inhibitor group. The cells were cultured for 6 days and collected for subsequent experiments 2 days after transfection.

RESULTS

Diabetic modeling impaired the erectile function in rats, and miR-100 reversed this effect. By measuring autophagy-related proteins such as mTOR/Raptor/Beclin1/p62/LC3B, we found that miR-100 could suppress the expression of mTOR and induce autophagy. The analysis of the eNOS/NO/cGMP axis function indicated that impaired endothelial function was improved by miR-100. By evaluating the TGF-β1/CTGF/Smad2/3 and NF-κB/TNF-α pathways, we found that miR-100 could lower the level of inflammation and fibrosis, which contributed to the improvement of the erectile function. Cellular experiments can be used as supporting evidence for these findings.

CONCLUSION

MiR-100 can improve the erectile function by inhibiting mTOR and thus inducing autophagy, improving the endothelial function through the eNOS/NO/cGMP axis, and exerting antifibrotic and anti-inflammatory effects, which may provide new ideas and directions for the treatment of DMED.

Oxidative Stress and Erectile Dysfunction: Pathophysiology, Impacts, and Potential Treatments

Erectile dysfunction (ED) is a prevalent condition affecting men's sexual health, with oxidative stress (OS) having recently been identified as a significant contributing causative factor. This narrative review aims to elucidate the role of OS in the pathophysiology of ED, focusing on impact, mechanisms, and potential therapeutic interventions. Key findings indicate that OS disrupts endothelial function and nitric oxide (NO) signaling, crucial for erectile function. Various sources of reactive oxygen species (ROS) and their detrimental effects on penile tissue are discussed, including aging, diabetes mellitus, hypertension, hyperlipidemia, smoking, obesity, alcohol consumption, psychological stress, hyperhomocysteinemia, chronic kidney disease, and sickle cell disease. Major sources of ROS, such as NADPH oxidase, xanthine oxidase, uncoupled endothelial NO synthase (eNOS), and mitochondrial electron transport, are identified. NO is scavenged by these ROS, leading to endothelial dysfunction characterized by reduced NO availability, impaired vasodilation, increased vascular tone, and inflammation. This ultimately results in ED due to decreased blood flow to penile tissue and the inability to achieve or maintain an erection. Furthermore, ROS impact the transmission of nitrergic neurotransmitters by causing the death of nitrergic neurons and reducing the signaling of neuronal NO synthase (nNOS), exacerbating ED. Therapeutic approaches targeting OS, including antioxidants and lifestyle modifications, show promise in ameliorating ED symptoms. The review underscores the need for further research to develop effective treatments, emphasizing the interplay between OS and vascular health in ED. Integrating pharmacological and non-pharmacological strategies could enhance clinical outcomes for ED patients, advocating for OS management in ED treatment protocols to improve patient quality of life.

Autophagy in erectile dysfunction: focusing on apoptosis and fibrosis

In most types of erectile dysfunction, particularly in advanced stages, typical pathological features observed are reduced parenchymal cells coupled with increased tissue fibrosis. However, the current treatment methods have shown limited success in reversing these pathologic changes. Recent research has revealed that changes in autophagy levels, along with alterations in apoptosis and fibrosis-related proteins, are linked to the progression of erectile dysfunction, suggesting a significant association. Autophagy, known to significantly affect cell fate and tissue fibrosis, is currently being explored as a potential treatment modality for erectile dysfunction. However, these present studies are still in their nascent stage, and there are limited experimental data available. This review analyzes erectile dysfunction from a pathological perspective. It provides an in-depth overview of how autophagy is involved in the apoptotic processes of smooth muscle and endothelial cells and its role in the fibrotic processes occurring in the cavernosum. This study aimed to develop a theoretical framework for the potential effectiveness of autophagy in preventing and treating erectile dysfunction, thus encouraging further investigation among researchers in this area.

The Role of Autophagy in Erectile Dysfunction

Autophagy is a conservative lysosome-dependent material catabolic pathway, and exists in all eukaryotic cells. Autophagy controls cell quality and survival by eliminating intracellular dysfunction substances, and plays an important role in various pathophysiology processes. Erectile dysfunction (ED) is a common male disease. It is resulted from a variety of causes and pathologies, such as diabetes, hypertension, hyperlipidemia, aging, spinal cord injury, or cavernous nerve injury caused by radical prostatectomy, and others. In the past decade, autophagy has begun to be investigated in ED. Subsequently, an increasing number of studies have revealed the regulation of autophagy contributes to the recovery of ED, and which is mainly involved in improving endothelial function, smooth muscle cell apoptosis, penile fibrosis, and corpus cavernosum nerve injury. Therefore, in this review, we aim to summarize the possible role of autophagy in ED from a cellular perspective, and we look forward to providing a new idea for the pathogenesis investigation and clinical treatment of ED in the future.

Autophagy, a critical element in the aging male reproductive disorders and prostate cancer: a therapeutic point of view

Autophagy is a highly conserved, lysosome-dependent biological mechanism involved in the degradation and recycling of cellular components. There is growing evidence that autophagy is related to male reproductive biology, particularly spermatogenic and endocrinologic processes closely associated with male sexual and reproductive health. In recent decades, problems such as decreasing sperm count, erectile dysfunction, and infertility have worsened. In addition, reproductive health is closely related to overall health and comorbidity in aging men. In this review, we will outline the role of autophagy as a new player in aging male reproductive dysfunction and prostate cancer. We first provide an overview of the mechanisms of autophagy and its role in regulating male reproductive cells. We then focus on the link between autophagy and aging-related diseases. This is followed by a discussion of therapeutic strategies targeting autophagy before we end with limitations of current studies and suggestions for future developments in the field.

Combining effect of camellia oil and squalene on hyperlipidemia-induced reproductive damage in male rats

Introduction

Camellia oil (CO), a common edible oil in China, contains a variety of active ingredients. In this study, we explored the combining effect and optimal feeding time of CO and squalene on hyperlipemia-induced reproductive damage rats and probably provided supportive data for use of CO for health benefits.

Methods

We established the hyperlipidaemia-induced reproductive damage model, and then the successfully modeled rats were randomly classified into four groups including a model control (MC) group, a camellia oil (CO) group, a camellia oil + squalene (COS) group, and a sildenafil (SN) group, which were feeding with different subjects during days 30 and 60. The normal (NC) group was fed under the same conditions.

Results

Our results showed that compared with the MC group, the CO, COS, and SN groups could significantly decline the serum TG, TC and LDL-C levels, increase the serum testosterone levels, the sperm counts in epididymidis and organ coefficients of penises, and no pathological change in penis and testis at days 30 and 60. Compared with the pure CO, the mixture of CO and squalene could significantly enhance the effect of decreasing the concentrations of TG, TC, and LDL-C and increasing the serum testosterone level and sperm count of epididymal tail, and the results of day 30 were better than those of day 60.

Discussion

CO and squalene have a combining effect on lowering blood lipid, improving the level of testosterone and the number of epididymal tail sperm, and promoting the recovery of erectile and sexual function on hyperlipidemia-induced reproductive damage rats on day 30.

Hyperuricaemia is an important risk factor of the erectile dysfunction: A systematic review and meta-analysis

Serum uric acid can affect endothelial function, and hyperuricaemia-induced endothelial dysfunction is involved in the pathogenesis of cardiovascular diseases. As endothelial dysfunction is also a main pathogenic mechanism of erectile dysfunction (ED), the present study aims to evaluate the relationship between hyperuricaemia and ED via systemic review and meta-analysis. Five cohort studies and six cross-sectional studies on hyperuricaemia and ED, including a total of 454,510 participants, were recruited. Odds ratio (OR) and the 95% confidence intervals (CI) were adopted to estimate the relationship between hyperuricaemia and ED. Overall risk on effects of urate-lowering therapy (ULT) were analysed. In addition, subgroup analyses on study design, populations, age stratification and the object were conducted. In the patients with hyperuricaemia, the risk of ED was 1.59-fold higher than (pooled OR = 1.59, 95% CI [1.29, 1.97]) the non-hyperuricaemia counterparts. Urate-lowing therapy (ULT) in these hyperuricaemia patients reduced the risk of ED by 27% (OR = 1.27, 95% CI [1.14, 1.41]). After subgroup analysis, the association between hyperuricaemia and ED remained significant apart from the >60 years subgroup. Hyperuricaemia is an important risk factor of ED, while ULT can reduce the risk of ED in hyperuricaemia. This study suggests that hyperuricaemia-associated endothelial dysfunction may also underlie the pathogenesis of ED in these patients.

Enhanced effects of salidroside on erectile function and corpora cavernosa autophagy in a cavernous nerve injury rat model

We explored the efficacy and mechanisms of salidroside treatment for erectile dysfunction induced by bilateral cavernous nerve injury (BCNI). Forty male rats were divided into four groups as follows: sham (cavernous nerves exposed only) (S); BCNI (M); BCNI + rapamycin (M + rapamycin); and BCNI + salidroside (M + salidroside). Erectile function in the rats was measured by intracavernosal pressure. Penile tissue was harvested for transmission electron microscopy, immunohistochemistry, immunofluorescence, Masson's trichrome staining, haematoxylin-eosin staining, TdT-mediated dUTP Nick End Labeling and western blotting. The M group exhibited a decrease in erectile responses and increased apoptosis and fibrosis compared to these in the S group. Meanwhile, nerve content and the penile atrophy index were also decreased in the M group. Treatment with salidroside and rapamycin for 3 weeks partially restored erectile function and significantly attenuated corporal apoptosis, fibrosis, nerve content and penile atrophy in the M group. Moreover, the autophagy level was further enhanced in the M + salidroside group, which was the same as that in the positive observation group (M + rapamycin). Salidroside treatment not only improved erectile function in rats with BCNI, but also inhibited apoptosis and fibrosis and ameliorated the loss of nerve content and endothelial and corpus cavernosum smooth muscle cells by promoting protective autophagy.

Human tissue kallikrein-1 protects against the development of erectile dysfunction in a rat model of hyperhomocysteinemia

The aim of this study was to investigate the mechanism by which a diet inducing high hyperhomocysteinemia (HHcy) leads to the deterioration of erectile function in rats and whether this is inhibited by expression of the human tissue kallikrein-1 (hKLK1) gene. We established a rat model of HHcy by feeding methionine (Met)-rich diets to male Sprague-Dawley (SD) rats. Male wild-type SD rats (WTRs) and transgenic rats harboring the hKLK1 gene (TGRs) were fed a normal diet until 10 weeks of age. Then, 30 WTRs were randomly divided into three groups as follows: the control (n = 10) group, the low-dose (4% Met, n = 10) group, and the high-dose (7% Met, n = 10) group. Another 10 age-matched TGRs were fed the high-dose diet and designated as the TGR+7% Met group. After 30 days, in all four groups, erectile function was measured and penile tissues were harvested to determine oxidative stress, endothelial cell content, and penis fibrosis. Compared with the 7% Met group, the TGR+7% Met group showed diminished HHcy-induced erectile dysfunction (ED), indicating the improvement caused by hKLK1. Regarding corpus cavernosum endothelial cells, hKLK1 preserved endothelial cell-cell junctions and endothelial cell content, and activated protein kinase B/endothelial nitric oxide synthase (Akt/eNOS) signaling. Fibrosis assessment indicated that hKLK1 preserved normal penis structure by inhibiting apoptosis in the corpus cavernosum smooth muscle cells. Taken together, these findings showed that oxidative stress, impaired corpus cavernosum endothelial cells, and severe penis fibrosis were involved in the induction of ED by HHcy in rats, whereas hKLK1 preserved erectile function by inhibiting these pathophysiological changes.

Novel noninvasive quantification of penile corpus cavernosum lesions in hyperlipidemia-induced erectile dysfunction in rabbits by two-dimensional shear-wave elastography

Structural alterations in fibroelastic components of the penile corpus cavernousum (CC) may impair its compliance, resulting in venous leakage and erectile dysfunction (ED). Our study evaluated the effectiveness of noninvasive two-dimensional shear-wave elastography (2-D SWE) in quantifying penile CC lesions in rabbits with hyperlipidemia-induced ED. A total of 12 New Zealand white rabbits were randomly divided into two groups. Six were fed a high-cholesterol diet containing 2% cholesterol and 8.5% lard for 10 weeks and the other six were fed normal diet as controls. We measured the shear-wave elastic quantitative (SWQ) value of penile CC by 2-D SWE. Erectile function was investigated by intracavernous injection of papaverine, and immunohistochemical (IHC) staining and the western blot analysis to determine the penile CC lesions. After 10 weeks, the SWQ values obtained from penile CC were remarkably higher in the high-cholesterol-fed compared with the control group, and the ΔICP (ICP plateau minus ICP baseline)/MAP (ICP: intracavernous pressure, MAP: mean arterial pressure) was markedly decreased. The IHC staining and western blot revealed extracellular matrix (ECM) accumulation in penile cavernous tissues, and the smooth muscle cell (SMC) phenotypic transition was affected, as indicated by reduced alpha-smooth muscle actin and calponin-1 expression and increased phospho-myosin light chain₂₀ (p-MLC₂₀)/MLC₂₀ and osteopontin expression. Hyperlipidemia resulted in ECM accumulation accompanied with SMC phenotypic transition in penile CC and impaired the erectile function eventually. These might, in turn, lead to variations in the SWQ values. It suggests that 2-D SWE may be a novel, noninvasive and effective approach that distinguishes penile CC lesions secondary to hyperlipidemia from normal.

Human Tissue Kallikrein 1 Improves Erectile Dysfunction of Streptozotocin-Induced Diabetic Rats by Inhibition of Excessive Oxidative Stress and Activation of the PI3K/AKT/eNOS Pathway

Objective

To investigate the protective effects and mechanisms of human tissue kallikrein 1 (hKLK1) on type 1 diabetes mellitus- (DM-) induced erectile dysfunction in rats. Materials and Methods. The homozygous transgenic rats (TGR) harboring the hKLK1 gene and age-matched wild-type Sprague Dawley rats (WTR) were involved, and intraperitoneal injection of streptozotocin was utilized to induce diabetes in rats. Forty-eight-week-old male rats were randomly divided into a WTR group, TGR group, diabetic WTR group (WTDM), diabetic TGR group (TGDM), and TGDM with HOE140 group (TGDMH), with eight rats in each group. Twelve weeks later, the erectile response of all rats was detected by cavernous nerve electric stimulation, and corpus cavernosums were harvested to evaluate the levels of cavernous oxidative stress (OS), apoptosis, fibrosis, and involved pathways. Moreover, cavernous smooth muscle cells (CSMC) and endothelial cells (EC) were primarily isolated to build a coculture system for a series of in vitro verification.

Results

The hKLK1 gene and age-matched wild-type Sprague Dawley rats (WTR) were involved, and intraperitoneal injection of streptozotocin was utilized to induce diabetes in rats. Forty-eight-week-old male rats were randomly divided into a WTR group, TGR group, diabetic WTR group (WTDM), diabetic TGR group (TGDM), and TGDM with HOE140 group (TGDMH), with eight rats in each group. Twelve weeks later, the erectile response of all rats was detected by cavernous nerve electric stimulation, and corpus cavernosums were harvested to evaluate the levels of cavernous oxidative stress (OS), apoptosis, fibrosis, and involved pathways. Moreover, cavernous smooth muscle cells (CSMC) and endothelial cells (EC) were primarily isolated to build a coculture system for a series of

Conclusions

hKLK1 preserves erectile function of DM rats through its antitissue excessive OS, apoptosis, and fibrosis effects, as well as activation of the PI3K/AKT/eNOS/cGMP pathway in the penis. Moreover, hKLK1 promotes relaxation and prevents high glucose-induced injuries of CSMC mediated by EC-CSMC crosstalk.

Rapamycin Supplementation May Ameliorate Erectile Function in Rats With Streptozotocin-Induced Type 1 Diabetes by Inducing Autophagy and Inhibiting Apoptosis, Endothelial Dysfunction, and Corporal Fibrosis

INTRODUCTION

Erectile dysfunction (ED), which is common in patients with diabetes mellitus (DM), seriously affects quality of life. Previous studies on the treatment of DM-induced ED (DMED) involve autophagy, but the specific effect and mechanism of treatment are not yet clear.

AIM

To investigate the effect and mechanism of rapamycin, an autophagy inducer, in ameliorating DMED.

METHODS

45 male Sprague-Dawley rats (7 weeks old) were used in the experiment. 8 rats were randomly selected as the control group; the other rats were treated with streptozotocin to induce type 1 DM. After 10 weeks, an apomorphine test was used to confirm DMED. Rats with DMED were intraperitoneally injected with rapamycin or vehicle for 3 weeks. Rats in the control group were injected with saline. Erectile function in rats was measured by electrically stimulating the cavernous nerve. The penises were then harvested for histologic examinations, ribonucleic acid (RNA), and protein levels of related factors by immunohistochemistry, immunofluorescence, real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and Western blot.

MAIN OUTCOME MEASURE

Erectile function was evaluated by maximum intracavernous pressure and mean arterial pressure. Penile tissues were used to perform histologic examinations and to determine the RNA and protein levels.

RESULTS

Erectile function, which was impaired in rats with DMED, was significantly ameliorated in the DMED + rapamycin group. The nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway was inhibited in the DMED group, and rapamycin significantly reduced this inhibition. The DMED group showed increased autophagy and apoptosis level compared with the non-diabetic group, and rapamycin increased the autophagy level and decreased the apoptosis level in the penis. Penile fibrosis was more severe in the DMED group than in the control group and was partially but significantly improved in the DMED + rapamycin group compared with the DMED group. The adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin kinase (mTOR) and PI3K/AKT/mTOR pathways were activated, and the mTOR (regulatory associated protein of mTOR, complex 1 [raptor])/p70 ribosomal protein S6 kinase (p70S6K) pathway was inhibited in the DMED group. Compared with DMED group, rapamycin led to lower AMPK/mTOR and AKT/mTOR pathways expression, a higher degree of mTOR (raptor)/p70S6K pathway inhibition, and no change in the mTORC2-related pathway.

CLINICAL IMPLICATIONS

Rapamycin was effective in restoring erectile function in type 1 DMED models.

STRENGTH AND LIMITATIONS

This study suggested for the first time that rapamycin, an autophagy inducer, is effective in restoring erectile function in rats with diabetes. However, the rat model might not represent the human condition.

CONCLUSION

Rapamycin improved erectile function in rats with DMED, likely by promoting autophagy, inhibiting apoptosis and fibrotic activity, and ameliorating endothelial function. These findings provide evidence of a potential treatment option for DMED. Lin H, Wang T, Ruan Y, et al. Rapamycin supplementation may ameliorate erectile function in rats with streptozotocin-induced type 1 diabetes by inducing autophagy and inhibiting apoptosis, endothelial dysfunction, and corporal fibrosis. J Sex Med 2018;15:1246-1259.

Melatonin Treatment Ameliorates Hyperhomocysteinemia-Induced Impairment of Erectile Function in a Rat Model

BACKGROUND

Hyperhomocysteinemia (HHcy) has been reported to be strongly correlated with the occurrence of erectile dysfunction (ED), but the mechanisms are not fully understood. Moreover, whether melatonin could be a potential treatment of HHcy-induced ED needs to be elucidated.

AIM

The aim of this study was to investigate the effects of melatonin on HHcy-induced ED and the potential mechanisms via modulating oxidative stress and apoptosis.

METHODS

The Sprague-Dawley (SD) rat model of HHcy was induced by 7% methionine (Met)-rich diets. 36 male SD rats were randomly distributed into 3 groups (n = 12 per group): control group, 7% Met group, and 7% Met + melatonin (Mel; 10 mg/kg, intraperitoneal injection) treatment group. After 4 weeks, the erectile function of all rats was evaluated by electrical stimulation of the cavernous nerve. Histologic and molecular alterations of the corpus cavernosum were also analyzed by immunofluorescence, immunohistochemistry, enzyme-linked immunosorbent assay, Western blotting, and polymerase chain reaction.

OUTCOMES

HHcy-induced ED rat models were successfully established, and Mel could preserve erectile function mainly through inhibiting oxidative stress via the Erk1/2/Nrf2/HO-1 signaling pathway and suppression of apoptosis.

RESULTS

Erectile function was significantly reduced in the rats with HHcy compared with that in the control group and was ameliorated in the HHcy rats treated with Mel. Compared with the control group, the rats in the HHcy group showed the following: (1) higher levels of total plasma homocysteine; (2) fewer neuronal nitric oxide synthase-positive cells in the corpus cavernous; (3) higher levels of reactive oxygen species and malondialdehyde, higher expression levels of nicotinamide adenine dinucleotide phosphate oxidase, and lower activities of superoxide dismutase, indicating an overactivated oxidative stress; (4) lower expression levels of Erk1/2/Nrf2/HO-1 signaling pathway components; and (5) higher levels of apoptosis, as determined by the expression levels of Bax, Bcl-2, and caspase 3. Mel treatment improved the erectile response, as well as histologic and molecular alterations.

CLINICAL TRANSLATION

Our study on a rodent model of HHcy provided evidence that Mel could be a potential therapeutic method for HHcy-related ED.

CONCLUSIONS

Mel treatment improves erectile function in rats with HHcy probably by potential antioxidative stress activity. This finding provides evidence for a potential new therapy for HHcy-induced ED. Tang Z, Song J, Yu, Z, et al. Melatonin Treatment Ameliorates Hyperhomocysteinemia-Induced Impairment of Erectile Function in a Rat Model. J Sex Med 2019;16:1506-1517.

Is lower low-density lipoprotein cholesterol associated with lower androgen and erectile dysfunction in men?

BACKGROUND AND AIMS

Therapeutic possibilities now exist to lower low-density lipoprotein cholesterol (LDL-C) to very low levels. However, substantial controversy remains in clinical practice with regard to its safety, and the question of whether low LDL-C levels per se may provoke adverse effects in humans arises. We aimed to explore the association of LDL-C with androgen and erectile dysfunction (ED) in a general population of men.

METHODS AND RESULTS

A total of 4203 men without hormone replacement therapy were enrolled from 22 sites in East China. Total testosterone (T) and Free T were assessed. Free androgen index (FAI) was calculated. The IIEF-5 questionnaire was used to assess ED. We found that free T and FAI gradually and markedly increased with increasing LDL-C levels. Using linear regression, after adjusting for age, educational level, economic status, smoking status, drinking status, BMI, diabetes, and use of lipid-lowering medication, LDL-C was positively associated with free T (B = 0.175, 95% CI: 0.084, 0.266) and FAI (B = 0.064, 95% CI: 0.016, 0.112). Meanwhile, there was a U-shaped curvilinear relationship between LDL-C and prevalence of ED. In the logistic regression analysis, compared to those with LDL-C among the 10th-90th percentile, the ORs of ED in men in the lowest and highest deciles were 1.938 (95% CI: 1.121, 3.349) and 1.804 (95% CI: 1.117, 2.916), respectively.

CONCLUSION

Lower LDL-C levels were significantly associated with lower free T and lower FAI in a general population of men. Moreover, both low and high levels of LDL-C might be risk factors for ED.

Human tissue kallikrein 1 ameliorates erectile function via modulation of macroautophagy in aged transgenic rats

Previously, we have demonstrated that human tissue kallikrein 1 (hKLK1) improves age-related erectile dysfunction (ED). Autophagy has been implicated in age-related diseases, including ED. However, the molecular mechanisms underlying hKLK1-mediated amelioration of age-related ED via regulation of autophagy remains unknown. To explore the potential mechanism, male wild-type Sprague-Dawley rats (WTR) and transgenic rats harboring human KLK1 (TGR) were bred till 4 or 18 months of age and divided into three groups: young WTR (yWTR) as the control group, aged WTR (aWTR) group, and aged TGR (aTGR) group. The erectile function of each rat was evaluated using cavernous nerve electrostimulation. The ratio of intracavernous pressure/mean arterial pressure (ICP/MAP) and total ICP were also measured. Western blotting, immunohistochemistry, and transmission electron microscopy were performed to detect the levels of autophagy. The expression levels of related signaling pathways were determined by western blotting and immunohistochemistry. We found that hKLK1 improved the impaired erectile function of aged rats. Compared to the yWTR and aTGR groups, the aWTR group showed reduced smooth muscle/collagen ratio, fewer autophagosomes, and lower expression of Beclin 1 and LC3-II, which indicate impaired smooth muscle function and low level of autophagy in the smooth muscle cells. Moreover, the PI3K/Akt/mTOR signaling pathway, which is considered to be a negative regulator of autophagy, was upregulated in the aWTR group. hKLK1 may partially restore erectile function in aged transgenic rats by upregulating protective autophagy via the PI3K/Akt/mTOR pathway. These observations indicate that hKLK1 is a potential gene therapy candidate for age-related ED.