Calpain-2 as a Treatment Target in Prenatal Stress-induced Epileptic Spasms in Infant Rats

Stress can induce a serious epileptic encephalopathy that occurs during early infancy. Recent studies have revealed that prenatal stress exposure is a risk factor for the development of infantile spasms. Our previous work demonstrates that prenatal stress with betamethasone-induced alterations to the expression of the K⁺/Cl⁻ co-transporter (KCC2) in gamma-aminobutyric acid (GABA) interneurons lowers the seizure threshold in exposed animals. Here, we further investigated the mechanisms involved in this KCC2 dysfunction and explored possible treatment options. We stressed Sprague-Dawley rats prenatally and further treated dams with betamethasone on gestational day 15, which increases seizure susceptibility and NMDA (N-Methyl-D-aspartate)-triggered spasms on postnatal day 15. In this animal model, first, we evaluated baseline calpain activity. Second, we examined the cleavage and dephosphorylation of KCC2. Finally, we checked the effect of a calpain inhibitor on seizure occurrence. The phosphorylated-N-methyl-D-aspartate Receptor 2B (NR2B):non-phosphorylated NR2B ratio was found to be higher in the cortex of the prenatally stressed beta-methasone model. We further found that the betamethasone model exhibited increased phosphorylation of calpain-2 and decreased phosphorylation of KCC2 and Glutamic acid decarboxylase 67 (GAD67). After using a calpain inhibitor in prenatal-stress rats, the seizure frequency decreased, while latency increased. GABAergic depolarization was further normalized in prenatal-stress rats treated with the calpain inhibitor. Our study suggests that calpain-dependent cleavage and dephosphorylation of KCC2 decreased the seizure threshold of rats under prenatal stress. Calpain-2 functions might, thus, be targeted in the future for the development of treatments for epileptic spasms.

The influence of ketamine on KCC2 in spinal cord of rat in remifentanil-induced hyperalgesia / 中华行为医学与脑科学杂志

Objective To explore the effect of pre-treatment of subcutaneous injection of ketamine on remifentanil induced hyperalgesia and K+/Cl-cotransporter 2,KCC2) expression on spinal cord of rats.Methods60 male adult SD rats were randomly divided into five groups(n=12 in each group):control group (group C),the incision group(group I),the incision plus remifentanil group(group I+R),the incision plus ketamine group(group I+K) and the incision plus remifentanil and ketamine group(group I+R+K).Mechanical withdrawal threshold (MWT) was evaluated at 24 hours before incision(T0),2 hours,6 hours,24 hours and 48 hours after incision(T1~T4).The lumbar spinal cords of rats were taken out at T4 time point and the KCC2 detected was detected by immunofluorescence analysis and western blot analysis.ResultsCompared with group C(T1(14.5±1.7)g,T2(14.2±1.1)g,T3(13.9±1.8)g,T4(14.2±1.1)g),MWT of other groups at T1 (I(5.6±0.8)g,I+R(3.2±1.0)g,I+K(6.8±1.7)g,I+R+K(5.1±1.6)g),T2 (I(6.9±1.0)g,I+R(4.3±1.2)g,I+K(8.0±1.4)g,I+R+K(6.2±1.5)g),T3 (I(7.6±0.9)g,I+R(5.4±1.1)g,I+K(10.3±1.2)g,I+R+K(7.1±1.1)g),T4 (I(8.9±1.1)g,I+R(7.5±1.4)g,I+K(11.3±1.2)g,I+R+K(8.3±1.2)g)and the expression of KCC2 at T4 decreased (P<0.05).Compared with group I(T1(5.6±0.8)g,T2(6.9±1.0)g,T3(7.6±0.9)g,T4(8.9±1.1)g),MWT of group I+R (T1(3.2±1.0)g,T2(4.3±1.2)g,T3(5.4±1.1)g,T4(7.5±1.4)g) decreased at all time points after incision (T1~T4)(P<0.05) and the expression of KCC2 at T4 decreased significantly (P<0.05).Compared with group I(T1(5.6±0.8)g,T2(6.9±1.0)g,T3(7.6±0.9)g,T4(8.9±1.1)g),MWT of group I+K (T1(6.8±1.7)g,T2(8.0±1.4)g,T3(10.3±1.2)g,T4(11.3±1.2)g) increased at all time points after incision (T1~T4)(P<0.05) and the expression of KCC2 at T4 increased (P<0.05).Compared with group I+R(T1(3.2±1.0)g,T2(4.3±1.2)g,T3(5.4±1.1)g,T4(7.5±1.4)g),MWT of group I+R+K (T1(5.1±1.6)g,T2(6.2±1.5)g,T3(7.1±1.1)g,T4(8.3±1.2)g) increased at all time points after incision (T1~T4)(P<0.05) and the expression of KCC2 at T4 increased (P<0.05).ConclusionPre-treatment of subcutaneous injection of ketamine can reduce the hyperalgesia of rats induced by remifentanil and reduce the inhibition of KCC2 expression on dorsal horn of spinal cord.

Change in expression of WNK1 in spinal cord of a rat model with bone cancer pain / 中国药理学通报

Aim To investigate the changes in the ex-pression of WNK1 in spinal cord of a rat model with bone cancer pain. Methods Female SD rats, weig-hing 170 ~200 g, were randomly divided into three groups:normal control group (group C, n=3), sham operation group ( group S, n =3 ) and bone cancer pain group ( group BCP, n =24 ) . Group C was not given any treatment, and group S was injected into the bone marrow of left tibia with 5 μl PBS solution while group BCP with 5 μl WALKER 256 mammary gland cancer cell suspension (approximately 1 × 105 cells). Mechanical paw withdrawal threshold ( MWT ) was measured at d1 before inoculation ( baseline) and d3, 6,9,10,11,12 after inoculation. Group S and C were sacrificed at d 12 while group BCP at d 3 ,6 ,9 ,12 after inoculation and spinal cord ( L4~6 ) were removed at different time points for detection of WNK1 mRNA ex-pression by qRT-PCR and WNK1 protein expression by Western blot. Results Compared with group C and S,group BCP’ s MWT started to decrease since d 3 ( P0. 05 ) while the protein expression upregulated since d6 and also showed an in-creasing trend to d 12 ( P<0. 01 ) . Conclusion The expression of WNK1 in spinal cord of a rat model with bone cancer pain increased abnormally, which may be involved in the occurrence and maintenance of a rat model with bone cancer pain.

Decreased Immunoreactivities of the Chloride Transporters, KCC2 and NKCC1, in the Lateral Superior Olive Neurons of Kanamycin-treated Rats

OBJECTIVES: From our previous study about the weak expressions of potassium-chloride (KCC2) and sodium-potassium-2 chloride (NKCC1) co-transporters in the lateral superior olive (LSO) in circling mice, we hypothesized that partially damaged cochlea of circling mice might be a cause of the weak expressions of KCC2 or NKCC1. To test this possibility, we reproduced the altered expressions of KCC2 and NKCC1 in the LSO of rats, whose cochleae were partially destroyed with kanamycin. METHODS: Rat pups were treated with kanamycin from postnatal (P)3 to P8 (700 mg/kg, subcutaneous injection, twice a day) and sacrificed for immunohistochemical analysis, scanning electron microscope (SEM) and auditory brain stem response. RESULTS: The SEM study revealed partially missing hair cells in P9 rats treated with kanamycin, and the hearing threshold was elevated to 63.8+/-2.5 dB SPL (4 ears) at P16. Both KCC2 and NKCC1 immunoreactivities were more prominent in control rats on P16. On 9 paired slices, the mean densities of NKCC1 immunoreactivities were 118.0+/-1.0 (control) and 112.2+/-1.2 (kanamycin treated), whereas those of KCC2 were 115.7+/-1.5 (control) and 112.0+/-0.8 (kanamycin treated). CONCLUSION: We concluded that weak expressions of KCC2 and NKCC1 in circling mice were due to partial destruction of cochleae.

Differential expression of Na+-K+-Cl- cotransporter 1 and K+-Cl- cotransporter 2 in the somata and dendrites of adult rat neocortical neurons[1] / 神经解剖学杂志

γ-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the adult brain. However, electrophysiological findings indicate that GABA exerts excitation in dendrites of mature eorlieal neurons. Little is known about morphological basis of GABA-medi-ated excitation in dendrites of mature cortical neurons. The effect of activated GABAA receptors is mainly determined by intraceUular chloride ion, whose active influx is mainly mediated by Na+-K +-Cl- cotransporter isoform 1 (NKCC1) and exclusion is mainly executed by K+-Cl- cotransporter isoform 2 ( KCC2 ). In the present study, by using immunofluorescent double staining and fluorescent density analysis, the expression and distribution of NKCCI- and KCC2-immunoreactivities in the dendrite and soma of adult rat neocortical neurons were detected in vivo and in vitro. The present results showed that both cytoplasm and membrane of neuronal soma and dendrite expressed NKCC1, while KCC2 only expressed in membrane of soma and dendrite. The results also indicated that the dendrites rather than the somata of neurons expressed more NKCC1 in adult rat neocortex, while the level of KCC2 expression in the dendrite membrane was similar to that in the membrane of somata. The similar expression pattern of NKCC1 and KCC2 in the dendrites and the somata was also observed in neocortical neurons cultured for 20 days in vitro. The present results suggest that the more NKCC1 expreasion in dendrites may contribute to GABA-mediated excitation in neuronal dendrites of adult neocortex neurons.