The cytohesin guanosine exchange factors (GEFs) are required to promote HGF-mediated renal recovery after acute kidney injury (AKI) in mice

Abstract

The lack of current treatment and preventable measures for acute kidney injury (AKI) in hospitalized patients results in an increased mortality rate of up to 80% and elevated health costs. Additionally, if not properly repaired, those who survive AKI may develop fibrosis and long-term kidney damage. The molecular aspects of kidney injury and repair are still uncertain. Hepatocyte growth factor (HGF) promotes recovery of the injured kidney by inducing survival and migration of tubular epithelial cells to repopulate bare tubule areas. HGF-stimulated kidney epithelial cell migration requires the activation of ADP-ribosylation factor 6 (Arf6) and Rac1 via the cytohesin family of Arf-guanine-nucleotide exchange factors (GEFs), in vitro. We used an ischemia and reperfusion injury (IRI) mouse model to analyze the effects of modulating this signaling pathway on kidney recovery. We treated IRI mice with either HGF, the cytohesin inhibitor SecinH3, or a combination of both. As previously reported, HGF treatment promoted rapid improvement of kidney function as evidenced by creatinine (Cre) and blood urea nitrogen (BUN) levels. In contrast, simultaneous treatment with SecinH3 and HGF blocks the ability of HGF to promote kidney recovery. Immunohistochemistry showed that HGF treatment promoted recovery of tubule structure, and had enhanced levels of active, GTP-bound Arf6 and GTP-Rac1. SecinH3 treatment, however, caused a dramatic decrease in GTP-Arf6 and GTP-Rac1 levels when compared to kidney sections from HGF-treated IRI mice. Additionally, SecinH3 counteracted the renal reparative effects of HGF. Our results support the conclusion that cytohesin function is required for HGF-stimulated renal IRI repair.

Inhibition of smooth muscle contraction and ARF6 activity by the inhibitor for cytohesin GEFs, secinH3, in the human prostate

“…To date, secinH3 has been rarely applied in vivo. The existing studies did not focus on possible hemodynamic effects, and therefore none have been reported to date (22,50). SecinH3 was tolerated for a minimum of 2-4 days in mice, although it induced hepatic insulin resistance (22,50).…”

“…Whereas the roles of RhoA and Rac, as well as their effector kinases, have been well established for contraction of prostate smooth muscle, no data on the involvement of GEFs or about the activating mechanisms of these GTPases in the prostate are available to date (14,26,55,63). Cytohesins are a group of GEFs, which exist in four different isoforms, referred to as cytohesin-1Ϫ4 (33,37,50). Apart from indirect, downstream Rac activation by cytohesin-dependent mechanisms, direct activation of ADP ribosylation factor 6 (ARF6) by cytohesin-2 has been repeatedly reported (30,33,50,57).…”

“…Cytohesins are a group of GEFs, which exist in four different isoforms, referred to as cytohesin-1Ϫ4 (33,37,50). Apart from indirect, downstream Rac activation by cytohesin-dependent mechanisms, direct activation of ADP ribosylation factor 6 (ARF6) by cytohesin-2 has been repeatedly reported (30,33,50,57). ARF6 is another small monomeric GTPase, which has been associated with actin organization and with functions depending on correct actin assembly in different studies (17).…”

ELMOD1 stimulates ARF6-GTP hydrolysis to stabilize apical structures in developing vestibular hair cells

“…8H-L,N). We also examined the distribution of activated ARF6 using an ARF6-GTP antibody (Torii et al, 2014;Reviriego-Mendoza and Santy, 2015). Levels of ARF6-GTP peaked around P8 ( Fig.…”

The small G protein Arf6 expressed in keratinocytes by HGF stimulation is a regulator for skin wound healing

“…In addition to the skin, other tissues, such as liver, lung and kidney, express Arf62345, suggesting that Arf6 plays an key role in wound healing-related pathophysiological phenomena in these tissues. In support of this assumption, cytohesin family members of Arf6 GEFs, which regulate Arf6 activity, are required for the HGF/c-Met signaling-dependent recovery of acute kidney injury46. Thus, it is of interesting to investigate pathophysiological roles of HGF/c-Met/Arf6 signaling in a wide variety of tissues.…”