Role of mitochondrial Bax, caspases, and MAPKs for ceramide-induced apoptosis in renal proximal tubular cells

Abstract

It remains elusive whether crosstalk exists among mitochondrial Bax, caspases, and mitogen-activated protein kinases (MAPKs), and whether epidermal growth factor (EGF), which may activate MAPKs, affects ceramide-induced apoptosis through the crosstalk in renal proximal tubular cells (RPTCs). Effect of ceramide on expression of mitochondrial Bax and phosphorylated (p)-ERK, p38MAPK and JNK, that of MAPKs inhibition, and of EGF in the presence or absence of MAPKs inhibition on ceramide-induced apoptosis were examined in HK-2 cells. Apoptosis and expression of mitochondrial Bax and p-MAPKs were measured by Hoechst 33258 staining and Western blotting. C2-ceramide, but not dihydroC2-ceramide, inactive C2-ceramide, induced apoptosis at 24 h. C2-ceramide enhanced the mitochondrial Bax expression at 1 h, which was peaked at 3-6 h and decreased at 24 h, but remained increased, compared to control. An inhibitor of caspases, zVAD-fmk, ameliorated ceramide-induced apoptosis, suggesting a role of caspases for ceramide-induced apoptosis. C2-ceramide enhanced the expression of p-ERK and p-p38MAPK, but not p-JNK, at 1 h, which was increased till 24 h. An inhibitor of ERK, PD98059, or of p38MAPK, SB202190, failed to affect C2-ceramide-induced apoptosis. EGF, which enhanced the expression of p-ERK and p-p38MAPK but not p-JNK, ameliorated C2-ceramide-induced apoptosis without affecting mitochondrial Bax. Inhibition of ERK or p38MAPK failed to abolish the protective effect of EGF on C2-ceramide-induced apoptosis. Mitochondrial Bax and caspases, but not MAPKs, play a role for ceramide-induced apoptosis in RPTCs. EGF ameliorates ceramide-induced apoptosis in Bax- and MAPKs-independent pathways. The mechanism of ceramide-induced apoptosis and anti-apoptotic effect of EGF deserves further investigations.

Human adipose-derived mesenchymal stem cells repair cisplatin-induced acute kidney injury through antiapoptotic pathways

“…Apoptosis and necrosis of tubular cells have been considered as the major consequences of cisplatin-induced AKI (6,10,36). Human AD-MSCs have been shown to exhibit antiapoptotic capacity in vivo (23,28).…”

“…BAX and Bcl-2 are two key regulators (proapoptotic and antiapoptotic, respectively) of apoptosis. Previous studies have demonstrated that MSC engraftment downregulates the expression level of BAX, but upregulates the expression level of Bcl-2 in kidneys with AKI, which modulates their expression back to a control level (13,23,36). In the current in vitro co-culture system, the expression patterns of three key regulators (p38, BAX and Bcl-2) of apoptosis were clearly demonstrated following AD-MSC treatment, which was an important addition to the in vivo data demonstrating that AD-MSCs are able to effectively regulate apoptotic proteins (23).…”

“…The p38 mitogen-activated protein kinase (MAPK) signaling pathway plays a significant role in apoptosis (35), and AD-MSCs have been shown to strongly inhibit the phosphorylation of p38 in cisplatin-induced AKI in vivo (23). Furthermore, Bcl-2 family members, who are crucial regulators of apoptosis, have been demonstrated to play key roles in AKI induced by cisplatin (36). However, whether the apoptotic function of MSCs, particularly AD-MSCs, results from cell fusion or the secretion of certain factors is yet to be determined.…”

Ceramide-Induced Apoptosis in Renal Tubular Cells: A Role of Mitochondria and Sphingosine-1-Phoshate

“…In vivo studies show that ceramide is accumulated in kidneys exposed to anti-glomerular membrane (GBM) antibody [ 52 ], nephrotoxins such as carbon tetrachloride [ 67 ] and isoflurane [ 62 ], developing kidney [ 68 , 69 ], ischemia/reperfusion (I/R) injury [ 51 , 52 ], glycerol-induced myohemoglobinuria [ 52 ], and obstructive nephropathy [ 70 ]. These stimuli can induce apoptosis, and an apoptogenic role of ceramide is further supported by the ability of exogenous ceramide to induce apoptosis in RTCs [ 50 , 63 , 68 , 71 ].…”

Downregulation of insulin-like growth factor binding protein 5 is involved in intervertebral disc degeneration via the ERK signaling pathway

“…Conversely, the phosphorylation of these kinases was enhanced in IGFBP5 knockdown cells, which was confirmed by Western blot and RT-PCR analyses. In addition, the activity of ERK pathway associated proteins, such as Bax (Iwayama and Ueda, 2013; Ma et al, 2014; Yating et al, 2015) and caspase-3 (Sudo and Minami, 2011; Wang et al, 2011), and the downregulation of antiapoptotic proteins, such as Bcl2 (Mebratu and Tesfaigzi, 2009; Roskoski, 2012; Sudo and Minami, 2010), is associated with the upregulation of apoptosis execution. Our results obtained from the qRT-PCR and Western blot analyses indicated that the Bax and caspase-3 levels were significantly increased, while the level of Bcl2 was significantly decreased in the IGFBP5-shRNA group.…”