Hypoxia-induced autophagy promotes human prostate stromal cells survival and ER-stress

https://doi.org/10.1016/j.bbrc.2015.07.086Get rights and content

Highlights

  • Autophagy is induced in human prostatic stromal cells under hypoxic stress.

  • Autophagy induced by hypoxia promotes cell survival in human prostatic stromal cells.

  • Hypoxia-induced cell survival may be involved in ER Stress.

  • Hypoxia induces autophagy through ER stress.

Abstract

Benign prostatic hyperplasia (BPH) is emerging as one of the most common diseases seriously threatening the health of elderly men. Accumulating evidences indicate that hypoxia could induce BPH. However, the underlying mechanism of BPH induced by hypoxia is not clear. In the study, hypoxia-induced autophagy could promote cell survival and endoplasmic reticula stress (ER stress) in WPMY-1 cells. Cell viability induced by hypoxia could been decreased by autophagy inhibitors (3-methyladenine, bafilomycin A1) or siRNA interference in two autophagy genes (Beclin1, ATG5) in WPMY-1 cells. Furthermore, ER stress was present in hypoxia-treated WPMY-1 cells, while autophagy and cell survival could been inhibited by C/EBP-homologous protein siRNA (CHOP), which is an important protein of ER stress pathway. Taken together, our data support a novel model that autophagy as a cytoprotective response promotes cell survival via ER stress under hypoxia in human prostate stromal cells.

Introduction

Benign prostatic hyperplasia (BPH) seriously affects the physical and psychological health and the living quality of patients, especially in elderly men [1], [2]. According to epidemiological investigation, the incidence of BPH is more than 50% among middle aged and senile men over the age of 50; whereas for men over 80 years old, the incidence is as high as 90% [3], [4]. With its increasing morbidity and mortality, BPH brings serious harm to the life and health of elderly men. Therefore, the disease is emerging as one of the important clinical topics on andrology. At present, although there are a wide variety of drugs for the treatment of BPH, the application of the drugs is very limited due to the strong side effects, drug dependency and incapacity to completely prevent the process of prostate hyperplasia, etc [5], [6]. Androgens and aging are acknowledged to play a permissive role in the occurrence and development of BPH, but they can not fully explain the occurrence and development of BPH. Recently, increasing evidences showed that hypoxia resulted from the impaired blood flow could induce development of BPH in the prostate [7], [8], [9], but the detailed mechanism remains to be determined.

Autophagy, which could degrade dysfunctional or unnecessary intracellular components, plays a critical role in protecting cells from various cell stresses [10], [11], [12], [13]. Autophagy has great influence on many physiological and pathological processes including the pathogenesis of prostate cancer [14]. Although it is reported that hypoxia-induced autophagy could lead to cell death [15], a growing body of studies suggests that autophagy also plays a protective role in hypoxic stress [16], [17]. An intriguing finding of the study by Pouysségur J et al. was that hypoxia-induced autophagy is a survival mechanism, and BNIP3 induces autophagy by disrupting the interaction of Beclin 1 with Bcl-2 and Bcl-XL [16], [17], [18]. In spite of these foundings, we still know very little about autophagy and its regulation in human prostatic stromal cell under hypoxia. Therefore, to further identify whether autophagy could be induced after hypoxia treatment, we investigated the autophagy formation and the specific role under hypoxia.

The endoplasmic reticulum (ER) stress plays a fundamental role in several pathological conditions including hypoxia [19], [20], [21], and also acts as an important regulator in prostatic hyperplasia following prostate ischemia by eliciting a wide spectrum of changes of its downstream signal pathways (angiogenesis, glucose metabolism, and cell survival, etc) [22], [23]. After prostatic stromal cells exposure to hypoxia, ER stress could be activated in a time dependence manner, and the cells secreted several growth factors and proinflammatory factors (TGF-β1, FGF-2, and IL-8, etc), which could induce prostatic hyperplasia [24]. A recent investigation found that ER stress plays an important role in determine cell survival or cell death, and could induce autophagy in different cell lines [25]. However, the role of ER stress was not discussed in hypoxia-induced autophagy, which function as a survival process was not clearly defined in benign prostatic hyperplasia.

In the present study, the relationships among ER stress, autophagy, and cell survival were investigated under hypoxia in human prostatic stromal cells (WPMY-1 cells). we proposed a hypothesis that hypoxia might lead to benign prostatic hyperplasia through inducing autophagy and ER stress.

Section snippets

Antibodies and reagents

3-methyladenine (3-MA, M9281), Bafilomycin A1 (Baf-A1, B1793), antibodies against MAP1LC3B (L7543), and ATG5 (WH0009474M1) were purchased from Sigma. Antibody against Beclin1 (612112) was purchased from BD Transduction Laboratories, Inc (Beverly, MA), whereas antibody against Actin (sc-10731) was obtained from Santa Cruz Biotechnology, Inc (Dallas, U.S.A.). The antibodies against CHOP (#3087) and p-eIF2α (Ser51, #9721) was obtained from Cell Signaling Technology. The GFP-MAP1LC3B plasmid was a

Autophagy is induced in human prostatic stromal cells under hypoxic stress

To confirm whether hypoxia could induce autophagy, we firstly examined the ratio of microtubule-associated protein 1 light chain 3 beta-II (MAP1LC3B-II) to actin, which is considered an accurate indicator of autophagy [28]. As shown in Fig. 1A, there was a gradual increase in the ratio of MAP1LC3B-II to Actin under hypoxia. Moreover, Baf-A1 treatment promoted the further accumulation of MAP1LC3B-II in human prostatic stromal cell after 24 h (Fig. 1A), suggesting that hypoxia could induce

Discussion

Based on the present results, it is firstly proposed that hypoxia induces benign prostatic hyperplasia by activating ER stress and autophagy in human prostatic stromal cells. The mechanism is supported by the following results: (1) Autophagy is induced in human prostatic stromal cells under hypoxic stress; (2) Autophagy induced by hypoxia promotes cell survival in human prostatic stromal cells; (3) Hypoxia-induced cell survival may be involved in ER Stress; and (4) Hypoxia induces autophagy

Acknowledgments

This study was supported by a grant from National Natural Science Foundation of China (No. 81400756, 81300475 and 81402099), and Application of Public Technology, Science Technology Department of Zhejiang Province (No. N20140400).

References (36)

  • Y.A. Gao et al.

    Benign prostatic hyperplasia: prostatic arterial embolization versus transurethral resection of the prostate-A prospective, randomized, and controlled clinical trial

    Radiology

    (2013)
  • M. Saito et al.

    Prostatic ischemia induces ventral prostatic hyperplasia in the SHR; possible mechanism of development of BPH

    Sci. Rep.

    (2014)
  • Y. Bostanci et al.

    Correlation between benign prostatic hyperplasia and inflammation

    Curr. Opin. Urol.

    (2013)
  • M.Z. Noman et al.

    Hypoxia-induced autophagy: a new player in cancer immunotherapy?

    Autophagy

    (2012)
  • S. Wilkinson et al.

    Growth factor signaling permits hypoxia-induced autophagy by a HIF1alpha-dependent, BNIP3/3L-independent transcriptional program in human cancer cells

    Autophagy

    (2009)
  • M.V. Blagosklonny

    Hypoxia, MTOR and autophagy: converging on senescence or quiescence

    Autophagy

    (2013)
  • N.Y. Lin et al.

    Autophagy regulates TNFalpha-mediated joint destruction in experimental arthritis

    Ann. Rheum. Dis.

    (2013)
  • H.J. Kung

    Targeting tyrosine kinases and autophagy in prostate cancer

    Horm. Cancer

    (2011)
  • Cited by (36)

    • Decoding ceRNA regulatory network and autophagy-related genes in benign prostatic hyperplasia

      2023, International Journal of Biological Macromolecules
      Citation Excerpt :

      It is a highly evolutionarily conserved and complex cellular process in eukaryotic cells, whereby the cytoplasmic proteins with long half-life and organelles are sequestered within autophagosomes and transported to lysosomes for degradation and recycling [8]. In the past decades, autophagy is involved in BPH development [9,10]. Androgen inhibition induces autophagy in prostate epithelial cells [10].

    • Decreased mitophagy aggravates benign prostatic hyperplasia in aged mice through DRP1 and estrogen receptor α

      2022, Life Sciences
      Citation Excerpt :

      Differentially expressed gene analysis showed that autophagy could be significantly associated with the development of prostatic hyperplasia [28]. Autophagy, induced by 5α reductase treatment by upregulating the expression of ATG9A, was reported to play a cytoprotective role under in prostate stromal cells [29,30]. Although the regulation of autophagy in relation to prostatic hyperplasia has been studied in in vitro, autophagy, particularly mitophagy, has never been studied in a mouse model of prostatic hyperplasia, which occurs spontaneously in old age.

    • Alteration in autophagy gene expression profile correlates with low sperm quality

      2021, Reproductive Biology
      Citation Excerpt :

      Hence, the down-regulated LC3B might induced decreased autophagy which reduced sperm motility and affected the sperm quality. Autophagy is a protective factor for cellular survival, and could promote normal development and maintenance of prostate gland, and contribute to spermatogenesis [6,8]. In our study, decreased autophagy gene expression in the case group indicated disordered balance in cell proliferation, differentiation and death that might lead to sperm cell death, reduced sperm mobility and eventually infertility.

    View all citing articles on Scopus
    1

    Nan Zhang and Na Ji contributed equally to this work.

    View full text