Intracellular Redox State Alters NMDA Receptor Response during Aging through Ca2+/Calmodulin-Dependent Protein Kinase II

“Introduction The NMDA receptor (NMDAR) is a major source of Ca 2 influx into the postsynaptic neuron during the induction of LTP at hippocampal CA3–CA1 synapses (Bliss and Collingridge, 1993).”

“The interaction of NMDARs with CaMKII has been proposed as a model of memory (Lisman et al., 2002) and recent work indicates that disruption of the interaction between CaMKII and NMDAR impairs the induction of LTP and spatial learning (Zhou et al., 2007).”

“CA1 region-specific knock-out of the NR1 subunit of the NMDAR abolishes LTP, in addition to impairing spatial memory (Tsien et al., 1996).”

“thermore, the enzymatic activity of these kinases can be regulated by the reduction and oxidation of the cysteine residues located in their structure (Raynaud et al., 1997; Griendling et al., 2000; Knapp and Klann, 2000).”

“, 1997; Billard and Rouaud, 2007), suggesting that age-related LTP and memory deficits are due to a decrease in the NMDARmediated component of synaptic transmission (Foster, 1999, 2007; Rosenzweig and Barnes, 2003), also referred to here as “NMDAR hypofunction.”

“Similarly, bath application of the CaMK inhibitor KN-62 (10 M, 45 min) (Tokumitsu et al., 1990), before and during the application of DTT, blocked (97.9 7.98%, n 5) the DTT-mediated increase in NMDAR-fEPSP in aged animals (Fig.”

“CaMKII contributes to DTT-mediated enhancement of NMDAR responses in aged animals NMDAR function is controlled by several intracellular kinases (Ben-Ari et al., 1992; Westphal et al., 1999; Li et al., 2001).”

“Furthermore, phosphatase activity decreases NMDAR function (Lieberman and Mody, 1994; Wang et al., 1994).”

“The redox state of the extracellular cysteine residues of the NMDARs have been implicated in regulating the NMDAR function in cell cultures and neonatal animals (Aizenman et al., 1989, 1990; Bernard et al., 1997; Choi and Lipton, 2000; Choi et al., 2001).”

“…and in tissue from neonates suggests that redox state is an important determinant of NMDAR function (Aizenman et al., 1989, 1990; Bernard et al., 1997; Choi and Lipton, 2000; Choi et al., 2001), possibly through oxidation of extracellular cysteine residues on the NMDAR (Lipton et al., 2002).”

“CaMKII contributes to DTT-mediated enhancement of NMDAR responses in aged animals NMDAR function is controlled by several intracellular kinases (Ben-Ari et al., 1992; Westphal et al., 1999; Li et al., 2001).”

“…in aged animals (Barnes et al., 1997; Billard and Rouaud, 2007), suggesting that age-related LTP and memory deficits are due to a decrease in the NMDARmediated component of synaptic transmission (Foster, 1999, 2007; Rosenzweig and Barnes, 2003), also referred to here as “NMDAR hypofunction.””

“Intracellular redox status contributes to age-related differences in NMDAR synaptic responses Previous research indicates that L-GSH is a cellular reducing agent that protects hippocampal neurons against oxidative stress (Shin et al., 2005; Shih et al., 2006; Yoneyama et al., 2008).”

“Our results indicate that a shift in the intracellular redox state during aging may cause or magnify the imbalance in the kinase/phosphatase activity, favoring phosphatases (Foster, 2007).”

“…are reminiscent of the agedependent effects of kinase and phosphatase inhibitors on the rapid component of synaptic transmission mediated by AMPARs (Norris et al., 1998b; Hsu et al., 2002; Foster, 2007) and suggest that PP1 activity contributes to a reduction in AMPAR and NMDAR components of…”

“CaMKII contributes to DTT-mediated enhancement of NMDAR responses in aged animals NMDAR function is controlled by several intracellular kinases (Ben-Ari et al., 1992; Westphal et al., 1999; Li et al., 2001).”

“” Numerous studies indicate that NMDARs contribute less Ca 2 to the induction of LTP in the area CA1 of aged hippocampus, when compared to the young hippocampus (Norris et al., 1998a; Shankar et al., 1998; Boric et al., 2008).”

“Our results are not likely due to CaM methionine oxidation since DTT selectively reduces cysteine residues (Ciorba et al., 1997; Cai and Sesti, 2009; Long et al., 2009).”

“…(Norris et al., 1998b; Hsu et al., 2002; Foster, 2007) and suggest that PP1 activity contributes to a reduction in AMPAR and NMDAR components of synaptic transmission (Foster et al., 2001; Morishita et al., 2005), a characteristic specific to senescent CA1 synapses (Rosenzweig and Barnes, 2003).”

“Furthermore, phosphatase activity decreases NMDAR function (Lieberman and Mody, 1994; Wang et al., 1994).”

“The redox state of the extracellular cysteine residues of the NMDARs have been implicated in regulating the NMDAR function in cell cultures and neonatal animals (Aizenman et al., 1989, 1990; Bernard et al., 1997; Choi and Lipton, 2000; Choi et al., 2001).”

“thermore, the enzymatic activity of these kinases can be regulated by the reduction and oxidation of the cysteine residues located in their structure (Raynaud et al., 1997; Griendling et al., 2000; Knapp and Klann, 2000).”

“…(Norris et al., 1998b; Hsu et al., 2002; Foster, 2007) and suggest that PP1 activity contributes to a reduction in AMPAR and NMDAR components of synaptic transmission (Foster et al., 2001; Morishita et al., 2005), a characteristic specific to senescent CA1 synapses (Rosenzweig and Barnes, 2003).”

“The interaction of NMDARs with CaMKII has been proposed as a model of memory (Lisman et al., 2002) and recent work indicates that disruption of the interaction between CaMKII and NMDAR impairs the induction of LTP and spatial learning (Zhou et al., 2007).”

“…and in tissue from neonates suggests that redox state is an important determinant of NMDAR function (Aizenman et al., 1989, 1990; Bernard et al., 1997; Choi and Lipton, 2000; Choi et al., 2001), possibly through oxidation of extracellular cysteine residues on the NMDAR (Lipton et al., 2002).”

“In contrast, the membrane-permeable PKC inhibitor, Bis-I (500 nM, 45 min) (Knapp and Klann, 2002) failed to block the DTT-mediated increase in the NMDAR-fEPSP (142.58 13.06%, n 6) (Fig.”

“Importantly, the NMDAR component of the synaptic response is decreased in aged animals (Barnes et al., 1997; Billard and Rouaud, 2007), suggesting that age-related LTP and memory deficits are due to a decrease in the NMDARmediated component of synaptic transmission (Foster, 1999, 2007; Rosenzweig…”

“Indeed, reduced CaMKII activity is associated with a specific decrease in synaptic NMDARs and decreased LTP (Gardoni et al., 2009).”

“…to regulating phosphorylation state of proteins, including glutamate receptors, synaptic CaMKII participates in protein–protein interactions with several proteins localized to the dendritic spine, which could ultimately alter NMDAR location and function (Lisman et al., 2002; Robison et al., 2005).”

“…and in tissue from neonates suggests that redox state is an important determinant of NMDAR function (Aizenman et al., 1989, 1990; Bernard et al., 1997; Choi and Lipton, 2000; Choi et al., 2001), possibly through oxidation of extracellular cysteine residues on the NMDAR (Lipton et al., 2002).”

“The aged brain exhibits an increase in oxidative damage (Foster, 2006; Poon et al., 2006), and a decrease in redox buffering capacity (Parihar et al., 2008); however, the effect of redox state on NMDAR function during aging has not been examined.”

“” Numerous studies indicate that NMDARs contribute less Ca 2 to the induction of LTP in the area CA1 of aged hippocampus, when compared to the young hippocampus (Norris et al., 1998a; Shankar et al., 1998; Boric et al., 2008).”

“However, L-GSH is relatively membrane impermeable such that exogenous application of L-GSH is not effective in increasing intracellular free thiols when compared to DTT (Mazor et al., 1996; Zou et al., 2001; Susankova et al., 2006).”

“…are reminiscent of the agedependent effects of kinase and phosphatase inhibitors on the rapid component of synaptic transmission mediated by AMPARs (Norris et al., 1998b; Hsu et al., 2002; Foster, 2007) and suggest that PP1 activity contributes to a reduction in AMPAR and NMDAR components of…”

“The aged brain exhibits an increase in oxidative damage (Foster, 2006; Poon et al., 2006), and a decrease in redox buffering capacity (Parihar et al., 2008); however, the effect of redox state on NMDAR function during aging has not been examined.”

“Intracellular redox status contributes to age-related differences in NMDAR synaptic responses Previous research indicates that L-GSH is a cellular reducing agent that protects hippocampal neurons against oxidative stress (Shin et al., 2005; Shih et al., 2006; Yoneyama et al., 2008).”

“Importantly, the NMDAR component of the synaptic response is decreased in aged animals (Barnes et al., 1997; Billard and Rouaud, 2007), suggesting that age-related LTP and memory deficits are due to a decrease in the NMDARmediated component of synaptic transmission (Foster, 1999, 2007; Rosenzweig…”

“Our results are not likely due to CaM methionine oxidation since DTT selectively reduces cysteine residues (Ciorba et al., 1997; Cai and Sesti, 2009; Long et al., 2009).”

“Age differences in the NMDAR response, which depend on kinase/phosphatase activity, are reminiscent of the agedependent effects of kinase and phosphatase inhibitors on the rapid component of synaptic transmission mediated by AMPARs (Norris et al., 1998b; Hsu et al., 2002; Foster, 2007) and suggest that PP1 activity co…”

“The aged brain exhibits an increase in oxidative damage (Foster, 2006; Poon et al., 2006), and a decrease in redox buffering capacity (Parihar et al., 2008); however, the effect of redox state on NMDAR function during aging has not been examined.”

“However, L-GSH is relatively membrane impermeable such that exogenous application of L-GSH is not effective in increasing intracellular free thiols when compared to DTT (Mazor et al., 1996; Zou et al., 2001; Susankova et al., 2006).”

“However, there is a debate concerning whether NMDAR subunit expression decreases at hippocampal CA3–CA1 synapses (Foster, 2002).”

“To examine the role of PP1, the PP1 inhibitor OA (1 M, 30 min) (Schnabel et al., 2001) was applied before and during application of DTT to aged hippocampal slices.”

“Intracellular redox status contributes to age-related differences in NMDAR synaptic responses Previous research indicates that L-GSH is a cellular reducing agent that protects hippocampal neurons against oxidative stress (Shin et al., 2005; Shih et al., 2006; Yoneyama et al., 2008).”

“Oxidation of methionine residues on CaM has been reported to decrease the ability of CaM to activate CaMKII (Robison et al., 2007).”

“thermore, the enzymatic activity of these kinases can be regulated by the reduction and oxidation of the cysteine residues located in their structure (Raynaud et al., 1997; Griendling et al., 2000; Knapp and Klann, 2000).”

“To test whether DTT effects were mediated by CaN, the CaN inhibitor FK-506 (10 M) (Norris et al., 2010) was bath applied 45 min before and during the application of DTT on aged hippocampal slices.”

“…redox state contributes to “NMDAR hypofunction” in the aged hippocampus Previous work demonstrates that NMDAR responses are reduced in the area CA1 of the hippocampus of aged rat brain (Barnes et al., 1997; Billard and Rouaud, 2007), possibly due to altered receptor function (Cady et al., 2001).”

“Age-related alterations that may contribute to the NMDAR deficits include altered subunit expression, composition, and splice forms (Magnusson et al., 2005, 2006).”

“The redox state of the extracellular cysteine residues of the NMDARs have been implicated in regulating the NMDAR function in cell cultures and neonatal animals (Aizenman et al., 1989, 1990; Bernard et al., 1997; Choi and Lipton, 2000; Choi et al., 2001).”

“This confirms previous reports that DTT does not influence AMPAR function (Gozlan et al., 1995; Abele et al., 1998).”

“…oxidation of CaMKII, rather than CaM, underlies the reduction in kinase activity and are consistent with a recent report demonstrating that oxidative stress induced by ischemia results in disulfide linkages on the cysteine residues of CaMKII, which decrease kinase activity (Shetty et al., 2008).”

“Age-related alterations that may contribute to the NMDAR deficits include altered subunit expression, composition, and splice forms (Magnusson et al., 2005, 2006).”

“This confirms previous reports that DTT does not influence AMPAR function (Gozlan et al., 1995; Abele et al., 1998).”

“Our results are not likely due to CaM methionine oxidation since DTT selectively reduces cysteine residues (Ciorba et al., 1997; Cai and Sesti, 2009; Long et al., 2009).”

“However, L-GSH is relatively membrane impermeable such that exogenous application of L-GSH is not effective in increasing intracellular free thiols when compared to DTT (Mazor et al., 1996; Zou et al., 2001; Susankova et al., 2006).”

“Indeed, the maintenance of the intracellular redox state is crucial for appropriate NMDA receptor function at hippocampal synapses during LTP processes (Bodhinathan et al., 2010), and also for neurogenic function within the SGZ of the hippocampus (Huang et al., 2012a).”

“Modulation of intracellular redox state has also been shown to alter the NMDA responses at hippocampal synapses in the aged, but not young rats (Bodhinathan et al., 2010), which may be relevant for the study of age-dependent cognitive decline.”