ABSTRACT
BACKGROUND: Considering long-term changes in renal sodium handling and blood pressure in maternal protein-restricted (LP) offspring, we assumed that the development of LP hypertension results from abnormal dorsal root ganglia (DRG) neurokinin expression associated with impaired responsiveness of renal sensory receptors, promoting a reduced urinary excretion of sodium. The present study investigates whether increased blood pressure in protein-restricted offspring would be associated with changes in the DRG cells and in renal pelvic wall expression of NK1R, SP and CGRP when compared to NP offspring. In addition, we assessed the tubular sodium handling, estimated by creatinine and lithium clearances before and after bilateral renal denervation in conscious LP offspring relative to age-matched NP counterparts. METHODS: Dams received a normal (NP) or low-protein diet (LP) during their entire pregnancy period. Male NP or LP offspring underwent bilateral surgical renal denervation before the 8-week renal functional test and blood pressure measurements. Immunofluorescence staining in DRG cells was assessed in optical sections by confocal laser scanning microscope. RESULTS: The current data demonstrated a sustained rise in blood pressure associated with a decrease in fractional excretion of sodium (FENa) by reducing post-proximal tubule sodium rejection in 16-wk old LP rats relative to age-matched NP counterparts. According to this study, bilateral renal denervation attenuated blood pressure and increased FENa in LP offspring. Furthermore, an immunohistochemical analysis showed a reduced expression of SP and CGRP in DRGs of LP when compared with NP rats. Renal pelvis of LP rats did not show a strong CGRP expression related to NP rats, whereas there was no change in SP immunostaining. CONCLUSIONS: These observations raise the possibility that impaired DRG and pelvic neurokinin expression associated with responsiveness of renal sensory receptors in 16-wk old LP offspring are conducive to excess renal reabsorption of sodium and development of hypertension in this programmed model.
Subject(s)
Blood Pressure/physiology , Diet, Protein-Restricted , Ganglia, Spinal/metabolism , Kidney Pelvis/metabolism , Neurokinin A/metabolism , Sodium/metabolism , Animals , Calcitonin Gene-Related Peptide/genetics , Calcitonin Gene-Related Peptide/metabolism , Catecholamines/analysis , Creatinine/metabolism , Female , Kidney/physiology , Lithium/analysis , Lithium/metabolism , Male , Microscopy, Fluorescence , Neurokinin A/genetics , Potassium/analysis , Rats , Rats, Wistar , Sodium/analysis , Substance P/genetics , Substance P/metabolismABSTRACT
Orofacial pain is associated with peripheral and central sensitization of trigeminal nociceptive neurons. Nerve injury results in release of chemical mediators that contribute to persistent pain conditions. The activation of the transient receptor potential vanilloid 1 (TRPV1), promotes release of calcitonin gene-related peptide (CGRP) and substance P (SP) from trigeminal nerve terminals. CGRP and SP contribute to the development of peripheral hyperalgesia. The expression of SP and CGRP by primary afferent neurons is rapidly increased in response to peripheral inflammation. CGRP receptor activation promotes activation of AMPA receptors, leading to increased firing of neurons which is reflected as central sensitization. In this study we investigated whether inferior alveolar nerve (IAN) injury influences AMPA receptors, CGRP, SP and TRPV1 expression in the trigeminal ganglion (TG). The relative expression of the protein of interest from naive rats was compared to those from injured rats and animals that received low level laser therapy (LLLT). IAN-injury did not change expression of GluA1, GluA2 and CGRP, but increased the expression of TRPV1 and SP. LLLT increases GluA1 and GluA2 expression and decreases TVPV1, SP and CGRP. These results, together with previous behavioral data, suggest that IAN-injury induced changes in the proteins analyzed, which could impact on nociceptive threshold. These data may help to understand the molecular mechanisms of pain sensitization in the TG.
Subject(s)
Facial Nerve Injuries/radiotherapy , Gene Expression Regulation/radiation effects , Low-Level Light Therapy , Mandibular Nerve/radiation effects , Trigeminal Ganglion/radiation effects , Animals , Calcitonin Gene-Related Peptide/genetics , Calcitonin Gene-Related Peptide/metabolism , Facial Nerve Injuries/genetics , Facial Nerve Injuries/metabolism , Facial Nerve Injuries/pathology , Male , Mandibular Nerve/metabolism , Mandibular Nerve/pathology , Neurons, Afferent/metabolism , Neurons, Afferent/pathology , Neurons, Afferent/radiation effects , Photic Stimulation/methods , Rats , Rats, Sprague-Dawley , Receptors, AMPA/genetics , Receptors, AMPA/metabolism , Signal Transduction , Substance P/genetics , Substance P/metabolism , TRPV Cation Channels/genetics , TRPV Cation Channels/metabolism , Trigeminal Ganglion/injuries , Trigeminal Ganglion/metabolismABSTRACT
STUDY DESIGN: Laboratory study. OBJECTIVE: The aims of this study were as follows: (1) to confirm that Substance P (SP) is expressed by nucleus pulposus (NP) and annulus fibrosus (AF) cells; (2) to determine the effect of SP on expression of inflammatory mediators in human disc cells and the effect of inflammatory mediators on the expression of SP; and (3) to characterize the relative expression of SP receptor isoforms in disc tissue and describe whether exposure to SP changes receptor expression. SUMMARY OF BACKGROUND DATA: SP, classically described as a neurotransmitter, acts as an inflammatory regulator in other tissue types, but its role within the intervertebral disc has not been characterized. METHODS: Human AF and NP cells from 7 individuals were expanded in monolayer and maintained in alginate bead culture. Cells were treated with SP or interleukin (IL)-1ß/tumor necrosis factor-α (TNF-α). After treatment, the cells were recovered and then RNA was isolated and transcribed into cDNA. Quantitative reverse-transcriptase polymerase chain reaction was performed to evaluate expression of inflammatory mediators and SP and its receptors. RESULTS: Disc cells treated with SP demonstrated significant upregulation of IL-1ß, IL-6, and IL-8 in NP and AF cells whereas significant upregulation of RANTES and TNF occurred only in the AF cells. AF and NP cells expressed SP at low levels; expression did not change significantly with SP treatment but was significantly upregulated after treatment with IL-1ß/TNF-α. Both SP receptor isoforms were expressed by NP and AF cells. CONCLUSION: SP upregulates inflammatory mediators in disc cells. SP and its receptors were expressed in both NP and AF cells, and expression did not change after treatment with SP but increased after treatment with IL-1ß/TNF-α. SP likely acts in an autocrine or paracrine manner in intervertebral disc cells and may be involved in "crosstalk" between disc cells and neurons, providing a potential mechanism for transmission of painful discogenic stimuli.