Expression and location of mRNAs encoding multiple forms of secretory phospholipase A₂ in the rat retina

Abstract

Low-molecular-weight secretory phospholipases A(2) (sPLA(2)s) are a subgroup of PLA(2)s, which are secreted, bind to receptors, and may act as intercellular signaling modulators. At least 10 different groups have been characterized in mammals, and there is expanding evidence of the significance of sPLA(2)s in neuronal signaling and survival [Kolko et al. (1996) J. Biol. Chem. 271: 32722-32728]. To date, no retinal sPLA(2)s have been cloned or characterized. We evaluated the existence and abundance of sPLA(2) subtypes in rat retina and explored their possible involvement in light-induced retinal damage. We designed primers to identify the sPLA(2)s in rat retina, based on known sequences of sPLA(2)-specific mRNAs in other tissues. RNA was isolated from rat retina, and cDNA was produced and used for PCR cloning to identify the novel subtypes of sPLA(2). Our study revealed the presence of mRNAs encoding sPLA(2)-IB, -X, -V, -IIE, -IIA, and -IIF in the retina, and quantification by real-time PCR revealed different abundances of the sPLA(2)s. We showed a time-dependent gene induction of sPLA(2)-X, -IB, and -V in light-induced retinal damage. We further explored the location of sPLA(2)-IB by in situ hybridization and immunohistochemistry. This study is the first to reveal the presence, abundance, and induction of mRNAs encoding sPLA(2)s in rat retina. We suggest that these enzymes are themselves intercellular signaling modulators of retinal cell function and perhaps also of retinal degeneration.

Cytochrome P450 2C Epoxygenases Mediate Photochemical Stress-induced Death of Photoreceptors

“…The responsible retinal cells, however, are unknown. Some secretory forms of PLA 2 are expressed in photoreceptors, and their expression is induced by light (61). These lines of evidence together with the endogenous expression of CYP2C55 and CYP2C29 in 661W cells (Fig.…”

A possible role for sPLA2 in oligodendrocyte death and spinal cord injury.

“…Interestingly, in separate studies sPLA 2 -IB increased following KA injection and electroconvulsive shock (Kolko et al, 2005), IB, V, and X increased after retinal damage (Kolko et al, 2004), and IIA increased following cerebral ischemia (Yagami et al, 2002b, Lin et al, 2004, Adibhatla and Hatcher, 2007. In comparison, this study found only the group II enzymes increased, while no change was observed in IB, and group X decreased following traumatic SCI.…”

“…Two sPLA 2 isoforms, IIA and IB, were chosen for this study because of their significant association with inflammation or highest expression in the CNS, respectively (Kolko et al, 2004).…”

“…The presence of sPLA 2 -IB, IIA, IIC, IIE, V, and X is well established within the mammalian brain (Molloy et al, 1998, Kolko et al, 2004 as is upregulation of certain isoforms following CNS injury (Kolko et al, 2004, Kolko et al, 2005, Adibhatla and Hatcher, 2007. However, only one study has demonstrated sPLA 2 -IIA and V protein in naïve spinal cords .…”

Characterization and location of secretory phospholipase A2 groups IIE, V, and X in the rat brain

“…Here, we found significant induction of all the sPLA 2 . Induction of the least-abundant sPLA 2 -X, however, was markedly higher as compared to the other sPLA 2 , indicating a special role of this subtype in neuronal damage (Kolko et al, 2004). Based on our studies in the neuroretina, we decided to further explore sPLA 2 in the brain.…”