In addition to the loss of motor function,~60% of patients develop pain after spinal cord injury.The cellular-molecular mechanisms are not well understood,but the data suggests that plasticity within the rostral,epice...In addition to the loss of motor function,~60% of patients develop pain after spinal cord injury.The cellular-molecular mechanisms are not well understood,but the data suggests that plasticity within the rostral,epicenter,and caudal penumbra of the injury site initiates a cellularmolecular interplay that acts as a rewiring mechanism leading to central neuropathic pain.Sprouting can lead to the formation of new connections triggering abnormal sensory transmission.The excitatory glutamate transporters are responsible for the reuptake of extracellular glutamate which makes them a critical target to prevent neuronal hyperexcitability and excitotoxicity.Our previous studies showed a sexually dimorphic therapeutic window for spinal cord injury after treatment with the selective estrogen receptor modulator tamoxifen.In this study,we investigated the anti-allodynic effects of tamoxifen in male and female rats with spinal cord injury.We hypothesized that tamoxifen exerts anti-allodynic effects by increasing the expression of glutamate transporters,leading to reduced hyperexcitability of the secondary neuron or by decreasing aberrant sprouting.Male and female rats received a moderate contusion to the thoracic spinal cord followed by subcutaneous slow-release treatment of tamoxifen or matrix pellets as a control(placebo).We used von Frey monofilaments and the“up-down method”to evaluate mechanical allodynia.Tamoxifen treatment decreased allodynia only in female rats with spinal cord injury revealing a sexdependent effect.The expression profile of glutamatergic transporters(excitatory amino acid transporter 1/glutamate aspartate transporter and excitatory amino acid transporter 2/glutamate transporter-1)revealed a sexual dimorphism in the rostral,epicenter,and caudal areas of the spinal cord with a pattern of expression primarily on astrocytes.Female rodents showed a significantly higher level of excitatory amino acid transporter-1 expression while male rodents showed increased excitatory amino acid transporter-2 expression compared with female rodents.Analyses of peptidergic(calcitonin gene-related peptide-α)and non-peptidergic(isolectin B4)fibers outgrowth in the dorsal horn after spinal cord injury showed an increased calcitonin gene-related peptide-α/isolectin B4 ratio in comparison with sham,suggesting increased receptive fields in the dorsal horn.Although the behavioral assay shows decreased allodynia in tamoxifen-treated female rats,this was not associated with overexpression of glutamate transporters or alterations in the dorsal horn laminae fibers at 28 days post-injury.Our findings provide new evidence of the sexually dimorphic expression of glutamate transporters in the spinal cord.The dimorphic expression revealed in this study provides a therapeutic opportunity for treating chronic pain,an area with a critical need for treatment.展开更多
Spinal cord injury（SCI） is a condition without a cure,affecting sensory and/or motor functions.The physical trauma to the spinal cord initiates a cascade of molecular and cellular events that generates a non-permiss...Spinal cord injury（SCI） is a condition without a cure,affecting sensory and/or motor functions.The physical trauma to the spinal cord initiates a cascade of molecular and cellular events that generates a non-permissive environment for cell survival and axonal regeneration.Among these complex set of events are damage of the blood-brain barrier,edema formation,inflammation,oxidative stress,demyelination,reactive gliosis and apoptosis.The multiple events activated after SCI require a multi-active drug that could target most of these events and produce a permissive environment for cell survival,regeneration,vascular reorganization and synaptic formation.Tamoxifen,a selective estrogen receptor modulator,is an FDA approved drug with several neuroprotective properties that should be considered for the treatment of this devastating condition.Various investigators using different animal models and injury parameters have demonstrated the beneficial effects of this drug to improve functional locomotor recovery after SCI.Results suggest that the mechanism of action of Tamoxifen administration is to modulate anti-oxidant,anti-inflammatory and anti-gliotic responses.A gap of knowledge exists regarding the sex differences in response to Tamoxifen and the therapeutic window available to administer this treatment.In addition,the effects of Tamoxifen in axonal outgrowth or synapse formation needs to be investigated.This review will address some of the mechanisms activated by Tamoxifen after SCI and the results recently published by investigators in the field.展开更多
Spinal cord injury （SCI） is a devastating condition that produces significant changes in the life- style of patients. Many molecular and cellular events are triggered after the initial physical impact to the cord. T...Spinal cord injury （SCI） is a devastating condition that produces significant changes in the life- style of patients. Many molecular and cellular events are triggered after the initial physical impact to the cord. Two major phases have been described in the field of SCI： an acute phase and late phase. Most of the therapeutic strategies are focused on the late phase because this provides an opportunity to target cellular events like apoptosis, demyelination, scar formation and axonal outgrowth. In this mini-review, we will focus on two agents （tamoxifen and a Src kinase family inhibitor known as PP2） that have been shown in our laboratory to produce neuroprotective （increase cell survival） and/or regenerative （axonal outgrowth） actions. The animal model used in our laboratory is adult female rat （N250 g） with a moderate contusion （12.5 mm） to the spinal cord at the T10 level, using the MASCIS impactor device. Tamoxifen or PP2 was administered by implantation of a 15 mg pellet （Innovative Research of America, Sarasota, FL, USA） or by intraperitoneal injections （1.5 mg/kg, every 3 days）, respectively, to produce a long-term effect （28 days）. Tamoxifen and the Src kinase inhibitor, PP2, are drugs that in rats with a moderate spinal cord injury promote functional locomotor recovery, increase spared white matter tissue, and stimulate axonal outgrowth. Moreover, tamoxifen reduces the formation of reactive oxygen species. Therefore, these drugs are possible therapeutic agents that have a neuroprotective/regen- erative activity in vertebrates with SCI.展开更多
The spinal cord has the ability to regenerate but the microenvironment generated after trauma reduces that capacity. An increase in Src family kinase （SFK） activity has been implicated in neuropathological condition...The spinal cord has the ability to regenerate but the microenvironment generated after trauma reduces that capacity. An increase in Src family kinase （SFK） activity has been implicated in neuropathological conditions associated with central nervous system trauma. Therefore, we hypothesized that a decrease in SFK activation by a long-term treatment with 4-amino-5-（4- chlorophenyl）-7-（t-butyl）pyrazolo[3,4-d]pyramidine （PP2）, a selective SFK inhibitor, after spinal cord contusion with the New York University （NYU） impactor device would generate a permissive environment that improves axonal sprouting and/or behavioral activity. Results demonstrated that long-term blockade of SFK activation with PP2 increases locomotor activity at 7, 14, 21 and 28 days post-iniury in the Basso, Beattie, and Bresnahan open field test, round and square beam crossing tests. In addition, an increase in white matter spared tissue and serotonin fiber density was observed in animals treated with PP2. However, blockade of SFK activity did not change the astrocytic response or infiltration of cells from the immune system at 28 days post-injury. Moreover, a reduced SFK activity with PP2 diminished Ephexin （a guanine nudeotide exchange factor） phosphorylation in the acute phase （4 days post-injury） after trauma. Together, these findings suggest a potential role of SFK in the regulation of spared tissue and/or axonal outgrowth that may result in functional locomotor recovery during the pathophysiology generated after spinal cord injury. Our study also points out that ephexinl phosphorylation （activation） by SFK action may be involved in the repulsive microenvironment generated after spinal cord injury.展开更多
基金supported by COBRE(P30GM149367)the Puerto Rico Science&Technology Trust(2022-00125)+1 种基金MBRS-RISE Program(R25 GM061838)SC1GM144032 program(all to JDM)。
文摘In addition to the loss of motor function,~60% of patients develop pain after spinal cord injury.The cellular-molecular mechanisms are not well understood,but the data suggests that plasticity within the rostral,epicenter,and caudal penumbra of the injury site initiates a cellularmolecular interplay that acts as a rewiring mechanism leading to central neuropathic pain.Sprouting can lead to the formation of new connections triggering abnormal sensory transmission.The excitatory glutamate transporters are responsible for the reuptake of extracellular glutamate which makes them a critical target to prevent neuronal hyperexcitability and excitotoxicity.Our previous studies showed a sexually dimorphic therapeutic window for spinal cord injury after treatment with the selective estrogen receptor modulator tamoxifen.In this study,we investigated the anti-allodynic effects of tamoxifen in male and female rats with spinal cord injury.We hypothesized that tamoxifen exerts anti-allodynic effects by increasing the expression of glutamate transporters,leading to reduced hyperexcitability of the secondary neuron or by decreasing aberrant sprouting.Male and female rats received a moderate contusion to the thoracic spinal cord followed by subcutaneous slow-release treatment of tamoxifen or matrix pellets as a control(placebo).We used von Frey monofilaments and the“up-down method”to evaluate mechanical allodynia.Tamoxifen treatment decreased allodynia only in female rats with spinal cord injury revealing a sexdependent effect.The expression profile of glutamatergic transporters(excitatory amino acid transporter 1/glutamate aspartate transporter and excitatory amino acid transporter 2/glutamate transporter-1)revealed a sexual dimorphism in the rostral,epicenter,and caudal areas of the spinal cord with a pattern of expression primarily on astrocytes.Female rodents showed a significantly higher level of excitatory amino acid transporter-1 expression while male rodents showed increased excitatory amino acid transporter-2 expression compared with female rodents.Analyses of peptidergic(calcitonin gene-related peptide-α)and non-peptidergic(isolectin B4)fibers outgrowth in the dorsal horn after spinal cord injury showed an increased calcitonin gene-related peptide-α/isolectin B4 ratio in comparison with sham,suggesting increased receptive fields in the dorsal horn.Although the behavioral assay shows decreased allodynia in tamoxifen-treated female rats,this was not associated with overexpression of glutamate transporters or alterations in the dorsal horn laminae fibers at 28 days post-injury.Our findings provide new evidence of the sexually dimorphic expression of glutamate transporters in the spinal cord.The dimorphic expression revealed in this study provides a therapeutic opportunity for treating chronic pain,an area with a critical need for treatment.
基金partially supported by COBRE(P20-GM103642)the MBRS-RISE Program(R25 GM061838)+1 种基金NIH-MARC(5T34GM007821-35)the RCMI program(5G12MD007600)
文摘Spinal cord injury（SCI） is a condition without a cure,affecting sensory and/or motor functions.The physical trauma to the spinal cord initiates a cascade of molecular and cellular events that generates a non-permissive environment for cell survival and axonal regeneration.Among these complex set of events are damage of the blood-brain barrier,edema formation,inflammation,oxidative stress,demyelination,reactive gliosis and apoptosis.The multiple events activated after SCI require a multi-active drug that could target most of these events and produce a permissive environment for cell survival,regeneration,vascular reorganization and synaptic formation.Tamoxifen,a selective estrogen receptor modulator,is an FDA approved drug with several neuroprotective properties that should be considered for the treatment of this devastating condition.Various investigators using different animal models and injury parameters have demonstrated the beneficial effects of this drug to improve functional locomotor recovery after SCI.Results suggest that the mechanism of action of Tamoxifen administration is to modulate anti-oxidant,anti-inflammatory and anti-gliotic responses.A gap of knowledge exists regarding the sex differences in response to Tamoxifen and the therapeutic window available to administer this treatment.In addition,the effects of Tamoxifen in axonal outgrowth or synapse formation needs to be investigated.This review will address some of the mechanisms activated by Tamoxifen after SCI and the results recently published by investigators in the field.
基金partially supported by the MBRS-RISE Program(R25 GM061838)COBRE(5P20-GM103642)
文摘Spinal cord injury （SCI） is a devastating condition that produces significant changes in the life- style of patients. Many molecular and cellular events are triggered after the initial physical impact to the cord. Two major phases have been described in the field of SCI： an acute phase and late phase. Most of the therapeutic strategies are focused on the late phase because this provides an opportunity to target cellular events like apoptosis, demyelination, scar formation and axonal outgrowth. In this mini-review, we will focus on two agents （tamoxifen and a Src kinase family inhibitor known as PP2） that have been shown in our laboratory to produce neuroprotective （increase cell survival） and/or regenerative （axonal outgrowth） actions. The animal model used in our laboratory is adult female rat （N250 g） with a moderate contusion （12.5 mm） to the spinal cord at the T10 level, using the MASCIS impactor device. Tamoxifen or PP2 was administered by implantation of a 15 mg pellet （Innovative Research of America, Sarasota, FL, USA） or by intraperitoneal injections （1.5 mg/kg, every 3 days）, respectively, to produce a long-term effect （28 days）. Tamoxifen and the Src kinase inhibitor, PP2, are drugs that in rats with a moderate spinal cord injury promote functional locomotor recovery, increase spared white matter tissue, and stimulate axonal outgrowth. Moreover, tamoxifen reduces the formation of reactive oxygen species. Therefore, these drugs are possible therapeutic agents that have a neuroprotective/regen- erative activity in vertebrates with SCI.
基金partially supported by the MBRS-RISE Program(R25 GM061838)MBRS-SCORE(SO6-GM08224)+2 种基金COBRE(5P20-GM103642)SNRP(NS39405)RCMI(8G12MD007600)
文摘The spinal cord has the ability to regenerate but the microenvironment generated after trauma reduces that capacity. An increase in Src family kinase （SFK） activity has been implicated in neuropathological conditions associated with central nervous system trauma. Therefore, we hypothesized that a decrease in SFK activation by a long-term treatment with 4-amino-5-（4- chlorophenyl）-7-（t-butyl）pyrazolo[3,4-d]pyramidine （PP2）, a selective SFK inhibitor, after spinal cord contusion with the New York University （NYU） impactor device would generate a permissive environment that improves axonal sprouting and/or behavioral activity. Results demonstrated that long-term blockade of SFK activation with PP2 increases locomotor activity at 7, 14, 21 and 28 days post-iniury in the Basso, Beattie, and Bresnahan open field test, round and square beam crossing tests. In addition, an increase in white matter spared tissue and serotonin fiber density was observed in animals treated with PP2. However, blockade of SFK activity did not change the astrocytic response or infiltration of cells from the immune system at 28 days post-injury. Moreover, a reduced SFK activity with PP2 diminished Ephexin （a guanine nudeotide exchange factor） phosphorylation in the acute phase （4 days post-injury） after trauma. Together, these findings suggest a potential role of SFK in the regulation of spared tissue and/or axonal outgrowth that may result in functional locomotor recovery during the pathophysiology generated after spinal cord injury. Our study also points out that ephexinl phosphorylation （activation） by SFK action may be involved in the repulsive microenvironment generated after spinal cord injury.
