Advancing age alters the expression of the ryanodine receptor 3 isoform in adult rat superior cervical ganglia

Abstract

Sympathetic nerves arising from the superior cervical ganglion (SCG) protect the cerebrovasculature during periods of acute hypertension and may play a role in homeostasis of target organs. The functions of these nerves depend on calcium release triggered by activation of ryanodine receptor (RyR) channels. The function of RyR channels is in part dependent on genetic expression and regulation by numerous protein modulators such as neuronal nitric oxide synthase (nNOS) neurons also found in the SCG. We have shown that release of calcium in SCG cells is altered during late maturation and advancing age. However, the underlying molecular mechanisms that may in part account for these data are elusive. Therefore we used molecular techniques to test the hypothesis that advancing age alters the pattern of genetic expression and/or protein levels of RyRs and their modulation by nNOS in the SCG in F344 rats aged 6, 12, and 24 mo. Surprisingly, ryr1 expression was undetectable in all age groups and ryr2 and ryr3 are the predominantly transcribed isoforms in the adult rat SCG. mRNA and protein levels for RyR2 isoform did not change with advancing age. However, ryr3 mRNA levels increased from 6 to 12 mo and declined from 12 to 24 mo. Similarly, RyR3 receptor protein levels also increased from 6 to 12 mo and declined from 12 to 24 mo. Because nNOS and the phosphorylation of the RyRs have been shown to modulate the function of RyRs, total phosphorylation and nNOS protein levels were analyzed in all age groups. Phosphorylation levels of the RyRs were similar in all age groups. However, nNOS protein levels increased from 6 to 12 mo followed by decline from 12 to 24 mo. These data suggest that advancing age selectively impacts the genetic expression and protein levels of RyR3 as well as modulatory nNOS protein levels. In addition, these data may part provide some insight into the possible changes in the function of RyRs that may occur with the normal aging process.

Amyloid-β-(1-42) Increases Ryanodine Receptor-3 Expression and Function in Neurons of TgCRND8 Mice

“…In a report by Lu et al (42), RyR-1 mRNA was increased significantly in aged human cortical tissue from individuals that were not demented, which suggests that increased RyRs may have a protective or positive role to play in neuronal function. Furthermore, it has been shown recently that RyR-3 mRNA and protein levels are increased in the superior cervical ganglia of aged rats and may serve to protect neurons from oxidative stress by modulating and increasing the protein expression of neuronal nitric-oxide synthase (43). A clearer picture of how RyRs are involved in balancing normal and pathological aging is required before they can be considered a feasible therapeutic target.…”

Calcium Regulation in Neuronal Function with Advancing Age: Limits of Homeostasis

“…However, as discussed above, protein levels are not the only important measure of RyR function, as activity of these channels is be regulated by several factors. Therefore, we extended our studies to investigate possible age-related changes in selected modulators of the RyR, including phosphorylation and nNOS levels which are known to modulate levels of cADPr (Vanterpool et al, 2006). We found that total phosphorylation of RyR channels was not altered with age, suggesting that steady state phosphorylation of RyR and hence regulation by this mechanism does not necessarily change with advancing age.…”

“…Based on results of our most current studies and reviews (Vanterpool et al, 2005(Vanterpool et al, , 2006Buchholz et al, 2007; and our previous work and that of others we propose the following: With advancing age an alteration in [Ca 2+ ]i signaling and function of peripheral adrenergic neurons results from a complex interplay of mechanisms, including increased sensitivity of the NA release mechanism to calcium, decline in SERCA function that alters calcium buffering and refilling of SER calcium stores, reduced RyR3 and decline in nNOS levels, which in turn modulates cADPr levels. This combination ultimately reduces the capacity of the SER to release calcium and abolishes the CICR process.…”

“…However, RyR2 and RyR3 mRNA are amply present in rat SCG, appearing to be the major receptor isoforms regulating calcium release from RyR-sensitive stores in all age groups. Furthermore, RyR3 mRNA and protein levels increased from 6 to 12 months and then decreased in senescent (24 month) animals, while RyR2 mRNA and protein levels remained constant with advancing age (Vanterpool et al, 2006). From these data showing the impact of age on mRNA and protein levels of RyR3 it is difficult to make a straightforward conclusion.…”

“…All three have been shown to participate as calcium release channels responsible for CICR (Ogawa et al, 2000). Because RyR are integral components in [Ca 2+ ]i signaling in SCG neurons, we tested the hypothesis that, with advancing age, expression of the predominant RyR isoform(s) in adult rat SCG, along with selective modulators, is altered (Vanterpool et al, 2006). For this study we used F-344 rats aged 6, 12 and 24 months and molecular techniques of reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assays (ELISA).…”