(853.3) Meprin β Modulates Cellular Proliferation Through The IL-6 Signaling Pathway In IRInduced Kidney Injury

Poster Board Number: E86

Shaymaa Abousaad (North Carolina Aamp;T State University), FAIHAA AHMED (North Carolina Aamp;T State University), Ayman Abouzeid (North Carolina Aamp;T State University), Elimelda Ongeri (North Carolina Aamp;T State University)

Inflammation plays a central role in the progression of kidney injury induced by ischemia/reperfusion (IR). Interleukin-6 (IL-6) trans-signaling has been shown to play a protective role by promoting repair processes in IR-induced renal injury. Meprin metalloproteases have been implicated in inflammation-induced kidney injury. Meprins proteolytically process the proinflammatory cytokine, IL-6, causing IL-6 inactivation. It was recently reported that meprins also cleave the IL-6 receptor (IL-6R). IL-6 binds to its receptor (IL-6R) in two ways, membrane bound (mbIL-6R), activating the classic IL-6 signaling pathway, or the soluble form (sIL-6R), activating the IL-6 trans-signaling pathway. IL-6 trans-signaling induces proliferation through either MAPK/ERK or PI3K/AKT pathway or in crosstalk with AKT/ERK. We previously showed that meprin β modulates cellular survival (BCL-2) through IL-6/JAK/STAT signaling pathway in IRinduced kidney injury. However, it’s not known how meprin β modulation of the IL-6 signaling pathway impacts the cellular proliferation in IR-induced acute kidney injury. Previous studies have shown that IL-6 binds to its receptor forming IL-6/IL6R complex, which binds to the membranebound gp130 dimer. This leads to activation phosphorylation of ERK and AKT pathways, which in turn leads to induction of cellular proliferation. PCNA is a cellular proliferation marker that is induced through activation of the IL-6 signaling pathway. The goal of the current study was to determine how meprin β modulation of the IL-6 signaling pathway impacts downstream cellular proliferation in IR-induced kidney injury. We used the unilateral IR as a model of renal inflammation in wild-type (WT) and meprin β knockout (βKO) male mice, with the contralateral kidneys serving as controls. The mice were sacrificed at 96 h post-IR, and kidney tissue processed for evaluation by RT-PCR and immunohistochemistry (IHC). To determine staining intensity, the tissue sections were evaluated for IL-6 and PCNA levels using light microscopy and imaged using Image J analysis Software. Statistical analysis of the optical density (OD) data utilized two-way ANOVA. Our PCR data showed a significant increase in mRNA levels for IL-6 and PCNA in WT and βKO mice (P ≤ 0.01) at 96 h-post IR when compared to WT control kidneys. However, the baseline mRNA levels for PCNA were significantly higher in βKO (P ≤ 0.01) when compared to WT kidneys. Immunohistochemical data showed significant increases (Plt;0.05) in IL-6 and PCNA in select tubules in both genotypes at 96 h post-IR when compared to control kidneys for each genotype. Data from immunofluorescence counterstaining of kidney tissues showed that the levels of IL-6, and PCNA were higher in meprin β-expressing proximal tubules (PTs), at 96 h post-IR when compared to the distal kidney tubules (DTs), which lack meprins. High levels of IL-6 were also present in the lumen of PTs and DTs from WT and βKO kidneys at 96 h post-IR, suggesting increased release into filtrate and subsequently into urine. However, high levels of PCNA were present in the lumen of PTs only from both genotypes at 96 h post-IR. In conclusion, our data shows that meprin β expression modulates cellular proliferation through the IL-6 signaling pathway in IR-induced kidney injury.