Elsevier

Life Sciences

Volume 256, 1 September 2020, 116736
Life Sciences

Protective effects of catalpol on diabetes mellitus-induced male reproductive damage via suppression of the AGEs/RAGE/Nox4 signaling pathway

https://doi.org/10.1016/j.lfs.2019.116736Get rights and content

Abstract

Aims

Diabetes mellitus (DM)-induced reproductive damage is an important cause of infertility for male DM patients, we herein evaluated the effects of catalpol on diabetic reproductive damage through the suppression of the AGEs/RAGE/Nox4 signaling pathway.

Methods

KK-Ay diabetic reproductive damage mice were administered with catalpol for 8 weeks, the testis/body weight ratio, testicular histopathology, the levels of endogenous hormone and the activity of testicular marker enzymes were determined. In vitro, the GC-2 cell injury model was induced by advanced glycation end-products (AGEs) and pretreated with catalpol. Cell viability, apoptosis, and oxidative stress markers were detected and the mechanism based on the AGEs/RAGE/Nox4 pathway was explored.

Key findings

Catalpol showed remarkable capacity on protecting diabetic reproductive damage by improving the histomorphology of the testes, increasing the testis/body weight ratio and activity of acid phosphatase (ACP), lactate dehydrogenase (LDH), gamma-glutamyl transferase (γ-GT). The reduced testosterone (T), luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels in DM mice were also reversed with catalpol intervention. Moreover, catalpol showed markedly effects of anti-oxidative in vivo and in vitro, which significantly down-regulated reactive oxygen species (ROS) levels and restored superoxide dismutase (SOD) activity, meanwhile decreased GC-2 cell apoptosis and Bax/Bcl-2 ratio. Moreover, the over-expression of receptors for AGEs (RAGE), NADPH oxidase type 4 (Nox4) and phosphorylation of nuclear transcription factor-κB p65 (NF-κB p65) were suppressed by catalpol.

Significance

Catalpol could alleviate DM-induced male reproductive damage by inhibiting oxidative stress-induced apoptosis and inflammation mediated by AGEs/RAGE/Nox4 signaling pathway.

Introduction

Diabetes mellitus (DM) is a chronic metabolic disease that has become a growing global problem. According to data published by the International Diabetes Federation in 2017, the number of people with DM worldwide will reach 424 million in 2017, a number that is expected to increase to 628 million by 2045. With the increasing prevalence and the younger age of patients presenting with DM, the effect of DM on the male reproductive system has come to attract greater attention. Approximately 90% of men with DM have disturbances in sexual function such as invirility, infertility, hypogonadism, retrograde ejaculation and so on [[1], [2], [3], [4]]. According to traditional Chinese medicine (TCM), DM reproductive dysfunction is due to “kidney essence and yin deficiency” while Western medicine studies have suggested that the pathogenesis of DM-induced reproductive damage is related to oxidative stress [5], endocrine imbalance [6,7], apoptosis, autophagy [8], endothelial dysfunction [9], neurological factors [10] and vasculopathy [11].

Recent investigations also demonstrated that high levels of advanced glycation end-products (AGEs) play a crucial role in the pathogenesis of DM-induced male reproductive damage. Chen et al. [12] reported that AGEs increased reactive oxygen species (ROS) production and induced TM3 cell apoptosis. Zhao et al. [13] found that AGEs significantly inhibited testosterone (T) production by inducing oxidative stress in the testicular interstitial cells of rats. The receptor for AGEs (RAGE) is one of a number of AGEs-binding proteins [14]. Overactivity of AGEs-RAGE is considered to be a direct cause of serious diabetic complications, containing nephropathy [15] and testicular damage [16]. NADPH oxidase has also been shown to play a pivotal role in boosting the development of DM-induced testicular injury [17,18]. Therefore, suppression of the AGEs-RAGE downstream signaling pathway is helpful for the prevention of DM-induced male reproductive damage.

Catalpol (Cat) is one of the effective components extracted from the TCM Radix Rehmanniae, which has been widely used in the treatment of DM. Some studies have shown that catalpol could improve diabetic encephalopathy [19], hyperglycemia [20] and neurotoxicity [21]. Additionally, catalpol has shown considerable anti-inflammatory [22] and anti-oxidative [23] effects. Catalpol has been demonstrated to suppress AGEs-induced inflammation through inhibition of ROS production and NF-κB p65 activity [24] and to alleviate diabetic nephropathy by inhibiting the AGEs-RAGE pathway [25]. However, there are few reports referring to the effect of catalpol on reproductive function, this study, therefore, aimed to explore the therapeutic effect of catalpol on DM-induced male reproductive damage. The AGEs/RAGE/Nox4 signaling pathway, which is responsible for oxidative stress during the pathological process, was also discussed (Fig. 1).

Section snippets

Reagents

Catalpol (HPLC ≥98%) was provided by Chengdu Rui-fen-si Biotechnology Co., Ltd. (China). Aminoguanidine (Ami) was provided by Sigma-Aldrich Inc. (USA). T, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) immunosorbent assay (ELISA) kits were provided from Shanghai Mei-Lian Biotechnology Co., Ltd (China). Hematoxylin and eosin (HE) assay kit was obtained from Beijing Solarbio Science & Technology Co., Ltd (China), while acid phosphatase (ACP), lactate dehydrogenase (LDH),

Catalpol restored DM-induced morphological alterations of testes in KK-Ay mice

As shown in the images from HE staining (Fig. 2A), in the control group, normal spermatogenic cells at various stages were observed arranged orderly from the basement membrane to the lumen, with a large number of mature sperm in the lumen. Pathological alterations of testicular tissue were observed in the model group and the basement membrane of testicular seminiferous tubules was incomplete and varied in thickness. Atrophied and recessed seminiferous tubules, degenerate or shriveled

Discussion

DM is a pathological condition of hyperglycemia that can result in damage to multiple systems, including dysfunction of the male reproductive system [28]. Catalpol is one of the effective components extracted from the TCM Radix Rehmanniae, which has been widely used in the treatment of DM and its complication [29]. This is the first report to prove the therapeutical effects of catalpol on DM-induced male reproductive damage. Also, the protective effects are likely related to hormone regulation,

Conclusion

In general, the findings of this study emphasize the potential of catalpol as an antioxidant for the treatment of DM-induced male reproductive damage. Catalpol could protect against DM-induced male reproductive damage by mitigating testicular structure, increasing sex hormone levels, as well as reducing oxidative stress-induced apoptosis and inflammation. The AGEs/RAGE/Nox4 signaling pathway has played an important role in this protective action. Nevertheless, further investigations are needed

Authorship contributions

Huiqin Xu and Yuping Chen participated in the research design. Ni Jiao, Yuping Chen, Yihui Zhu, Wei Wang, Mengxue Liu, and Wangli Ding participated in project administration. Ni Jiao and Yuping Chen performed data curation and formal analysis. Gaohong Lv, Jinfu Lu, and Bin Yu contributed new reagents and software analytic tools. Ni Jiao wrote the original draft. Huiqin Xu and Yuping Chen reviewed and edited the manuscript.

CRediT authorship contribution statement

Ni Jiao: Data curation, Formal analysis, Project administration, Writing - original draft. Yuping Chen: Conceptualization, Data curation, Formal analysis, Project administration, Writing - review & editing. Yihui Zhua: Project administration. Wei Wang: Project administration. Mengxue Liua: Project administration. Wangli Dinga: Project administration. Gaohong Lv: Resources, Software. Jinfu Lu: Resources, Software. Bin Yu: Resources, Software. Huiqin Xu: Conceptualization, Writing - review &

Declaration of competing interest

The authors all declare that they have no competing interests.

Acknowledgments

This work was supported by the National Natural Science Foundation of China (Nos. 81073111, 81374029 and 81874359), a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) (JKLPSE201604), the Natural Science Research of Jiangsu Higher Education Institutions of China (No. 17KJB360003) and College Students Innovation Training Program of Jiangsu Province (201810315066Y).

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