Phospholipase D1 mediates TNFalpha-induced inflammation in a murine model of TNFalpha-induced peritonitis.
BACKGROUND
Tumor Necrosis Factor alpha (TNFalpha) is a pleiotropic cytokine extensively studied for its role in the pathogenesis of a variety of disease conditions, including in inflammatory diseases. We have recently shown that, in vitro, that TNFalpha utilizes PLD1 to mediate the activation of NFkappaB and ERK1/2 in human monocytes. The aim of this study was to investigate the role(s) played by phospholipase D1 (PLD1) in TNFalpha-mediated inflammatory responses in vivo.


RESULTS
Studies were performed in vivo using a mouse model of TNFalpha-induced peritonitis. The role of PLD1 was investigated by functional genomics, utilizing a specific siRNA to silence the expression of PLD1. Administration of the siRNA against PLD1 significantly reduced PLD1 levels in vivo. TNFalpha triggers a rapid pyrogenic response, but the in vivo silencing of PLD1 protects mice from the TNFalpha-induced rise in temperature. Similarly TNFalpha caused an increase in the serum levels of IL-6, MIP-1alpha and MIP-1beta: this increase in cytokine/chemokine levels was inhibited in mice where PLD1 had been silenced. We then induced acute peritonitis with TNFalpha. Intraperitoneal injection of TNFalpha triggered a rapid increase in vascular permeability, and the influx of neutrophils and monocytes into the peritoneal cavity. By contrast, in mice where PLD1 had been silenced, the TNFalpha-triggered increase in vascular permeability and phagocyte influx was substantially reduced. Furthermore, we also show that the TNFalpha-mediated upregulation of the cell adhesion molecules VCAM and ICAM1, in the vascular endothelium, were dependent on PLD1.


CONCLUSIONS
These novel data demonstrate a critical role for PLD1 in TNFalpha-induced inflammation in vivo and warrant further investigation. Indeed, our results suggest PLD1 as a novel target for treating inflammatory diseases, where TNFalpha play key roles: these include diseases ranging from sepsis to respiratory and autoimmune diseases; all diseases with considerable unmet medical need.
Sethu
Swaminathan
S
Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
Pushparaj
Peter N
PN
Melendez
Alirio J
AJ
D000818:Animals; D001831:Body Temperature / Q000187:drug effects; D002199:Capillary Permeability / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000378:metabolism; D018925:Chemokines / Q000096:biosynthesis; D004195:Disease Models, Animal; D055785:Gene Knockdown Techniques; D007249:Inflammation / Q000150:complications / Q000201:enzymology* / Q000473:pathology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009000:Monocytes / Q000187:drug effects / Q000473:pathology; D020556:Neutrophil Infiltration / Q000187:drug effects; D010537:Peritoneum / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010538:Peritonitis / Q000097:blood / Q000150:complications / Q000201:enzymology* / Q000473:pathology*; D010739:Phospholipase D / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D015815:Cell Adhesion Molecules; D018925:Chemokines; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D010739:Phospholipase D; C106801:phospholipase D1
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