Identification of thrombospondin 1 (TSP-1) as a novel mediator of cell injury in kidney ischemia

Abstract

Thrombospondin 1 (TSP-1) is a matricellular protein that inhibits angiogenesis and causes apoptosis in vivo and in vitro in several cancerous cells and tissues. Here we identify TSP-1 as the molecule with the highest induction level at 3 hours of IR injury in rat and mouse kidneys subjected to ischemia/reperfusion (IR) injury using the DNA microarray approach. Northern hybridizations demonstrated that TSP-1 expression was undetectable at baseline, induced at 3 and 12 hours, and returned to baseline levels at 48 hours of reperfusion. Immunocytochemical staining identified the injured proximal tubules as the predominant sites of expression of TSP-1 in IR injury and showed colocalization of TSP-1 with activated caspase-3. Addition of purified TSP-1 to normal kidney proximal tubule cells or cells subjected to ATP depletion in vitro induced injury as demonstrated by cytochrome c immunocytochemical staining and caspase-3 activity. The deleterious role of TSP-1 in ischemic kidney injury was demonstrated directly in TSP-1 null mice, which showed significant protection against IR injury-induced renal failure and tubular damage. We propose that TSP-1 is a novel regulator of ischemic damage in the kidney and may play an important role in the pathophysiology of ischemic kidney failure.

Molecular Basis for the Regulation of Angiogenesis by Thrombospondin-1 and -2

“…More effective recovery is observed for kidney ischemia/reperfusion injury and the cutaneous flap assay in TSP-1-null mice as compared to wild-type mice (Thakar et al 2005;Isenberg et al 2007). TSP-1-null and CD47-null mice display decreased necrosis and significantly improved healing in the cutaneous flap model and full-thickness skin grafts.…”

“…Given the complexity of its interactions, however, efforts have been undertaken to identify and purify the regions of TSP-1 and TSP-2 that interrupt angiogenesis selectively. Several domains of TSP-1 have been shown to interfere with angiogenesis, including the TSRs and procollagen homology domain (Persson et al 1995;Guo et al 1997;Iruela-Arispe et al 1999;Reiher et al 2002;Thakar et al 2005). To illustrate this, mice with experimental B16F10 melanomas and Lewis lung carcinomas have been treated systemically with recombinant peptides composed of various combinations of the TSRs with and without the TGF-b-activating sequence of TSP-1, the RFK sequence (Miao et al 2001).…”

CD47 deficiency confers cell and tissue radioprotection by activation of autophagy

“…Mice that lack CD47 or its ligand THBS1 are profoundly resistant to a variety of ischemic injuries including soft tissue ischemia and ischemia/reperfusion, 48 liver and renal ischemia/reperfusion injury, 34,49 spinal cord injury, 50 focal cerebral ischemia 51 and radiation. This makes CD47 blockade or agents that downregulate its expression attractive approaches CD47 primes cells by stabilizing mRNA to engage the autophagy machinery in an efficient manner to insure cell survival.…”

Regulation of Cellular Redox Signaling by Matricellular Proteins in Vascular Biology, Immunology, and Cancer

“…In vivo, studies in Thbs1 -/-and Cd47 -/-mice indicate that the TSP1-CD47 axis limits blood flow and tissue survival under conditions of fixed ischemia (85, 100a) as well as ischemia-reperfusion (36,271,307), situations characterized by significant oxidative stress. Conversely, suppressing CD47 expression using an adenoviral siRNA vector protected myocardial tissue from ischemia-reperfusion injury in rats while elevating eNOS phosphorylation and NO production, decreasing gp91 phox and superoxide, decreasing tissue malondialdehyde, and increasing SOD activity (288).…”

“…For example, multiple studies have reported TSP1 induction under hypoxia (11,123,185,187) and in response to ischemia (52,219,241,260) or ischemia-reperfusion injuries (89,125,138,215,217,228,271), situations well known to upregulate ROS. This raises the intriguing hypothesis that ROS signaling may increase TSP1 expression.…”