Characterization of C3a and C5a Receptors in Rat Cerebellar Granule Neurons during Maturation

Abstract

There is now clear evidence that the Complement anaphylatoxin C3a and C5a receptors (C3aR and C5aR) are expressed in glial cells, notably in astrocytes and microglia. In contrast, very few data are available concerning the possible expression of these receptors in neurons. Here, we show that transient expression of C3aR and C5aR occurs in cerebellar granule neurons in vivo with a maximal density in 12-day-old rat, suggesting a role of these receptors during development of the cerebellum. Expression of C3aR and C5aR mRNAs and proteins was also observed in vitro in cultured cerebellar granule cells. Quantification of the mRNAs by real-time reverse transcription-PCR showed a peak of expression at day 2 in vitro (DIV 2); the C3aR and C5aR proteins were detected by Western blot analysis at DIV 4 and by flow cytometry and immunocytochemistry in differentiating neurons with a maximum density at DIV 4 -9. Apoptosis of granule cells plays a crucial role for the harmonious development of the cerebellar cortex. We found that, in cultured granule neurons in which apoptosis was induced by serum deprivation and low potassium concentration, a C5aR agonist promoted cell survival and inhibited caspase-3 activation and DNA fragmentation. The neuroprotective effect of the C5aR agonist was associated with a marked inhibition of caspase-9 activity and partial restoration of mitochondrial integrity. Our results provide the first evidence that C3aR and C5aR are both expressed in cerebellar granule cells during development and that C5a, but not C3a, is a potent inhibitor of apoptotic cell death in cultured granule neurons.

Gangliosides play pivotal roles in the regulation of complement systems and in the maintenance of integrity in nerve tissues

“…Besides roles in the induction of inflammation with complement activation and eventual neurodegeneration (23, 25), functions in development (32,33), neurogenesis in adults (34), and protection in disease-susceptible mutant mice like Tg/A␤ have been reported in ref. 35.…”

C5a receptor expression is associated with poor prognosis in urothelial cell carcinoma patients treated with radical cystectomy or nephroureterectomy

“…Although it has not yet been demonstrated in human UCC, C5aR signaling suppresses apoptosis, induces T-cell expansion via the enhanced expression of Bcl-2 (32) and enhances neuronal cell survival via inhibition of caspase-3 activation (33). C5a is present in the cancer microenvironment (17,20,23), where, by stimulation with C5a, the apoptosis of C5aR-expressing UCC may be suppressed; this supression facilitates the growth and development of cancer in concert with the C5a-elicited enhancement of proliferation (24) and invasiveness (22).…”

Delayed post-injury administration of C5a improves regeneration and functional recovery after spinal cord injury in mice

“…It was reported that the expression of the C5a receptor in neurones remained weak under normal physiological conditions but increased significantly when stimulated by inflammation [25], which could be a selfprotection response. For example, Mukherjee and Pasinetti [6] found that the neurones in the hippocampus that were pretreated with C5a showed high tolerance to glutamate, and Bénard et al [7] reported that the C5a receptor antagonist could promote neural survival. Our data also showed that a certain concentration of C5a could reduce the caspase-3 mediated apoptosis of injured neurones, and that this effect could be reversed by PMX53 administration.…”

“…However, it was reported recently that complement activation had another neuroprotective role [6][7][8][9] in addition to that involving the secondary injury [10,11], and C5a was thought to be the most important factor in this respect. Although C5a can induce the chemotactic response and mediate the early phase of inflammation that is harmful to cells at the lesion site [12,13], it can exert its neuroprotective effect by inhibiting neurone apoptosis [6,7,14] and promoting microglial phagocytosis [15,16], which is beneficial in alleviating the secondary injury.…”

“…Although C5a can induce the chemotactic response and mediate the early phase of inflammation that is harmful to cells at the lesion site [12,13], it can exert its neuroprotective effect by inhibiting neurone apoptosis [6,7,14] and promoting microglial phagocytosis [15,16], which is beneficial in alleviating the secondary injury. However, in terms of SCI, existing research is focused on the secondary injury caused by C5a, and it is not known whether it exerts a neuroprotective effect after SCI.…”