Involvement of Substance P (SP) and Its Related NK1 Receptor in Primary Sjögren's Syndrome (pSS) Pathogenesis

Primary Sjögren's Syndrome (pSS) is a systemic autoimmune disease that primarily attacks the lacrimal and salivary glands, resulting in impaired secretory function characterized by xerostomia and xerophthalmia. Patients with pSS have been shown to have impaired salivary gland innervation and altered circulating levels of neuropeptides thought to be a cause of decreased salivation, including substance P (SP). Using Western blot analysis and immunofluorescence studies, we examined the expression levels of SP and its preferred G protein-coupled TK Receptor 1 (NK1R) and apoptosis markers in biopsies of the minor salivary gland (MSG) from pSS patients compared with patients with idiopathic sicca syndrome. We confirmed a quantitative decrease in the amount of SP in the MSG of pSS patients and demonstrated a significant increase in NK1R levels compared with sicca subjects, indicating the involvement of SP fibers and NK1R in the impaired salivary secretion observed in pSS patients. Moreover, the increase in apoptosis (PARP-1 cleavage) in pSS patients was shown to be related to JNK phosphorylation. Since there is no satisfactory therapy for the treatment of secretory hypofunction in pSS patients, the SP pathway may be a new potential diagnostic tool or therapeutic target.

[Effects of moxibustion on serum levels of β-EP, SP and expression of IL-1β and COX-2 protein in brainstem in rats with migraine]

OBJECTIVE

To observe the effects of moxibustion at "Baihui" (GV 20) and "Dazhui" (GV 14) at different time points on the serum level of β-endorphin (β-EP), substance P (SP) and expression of interleukin-1β (IL-1β) and cyclooxygenase-2 (COX-2) protein in brainstem in rats with migraine, and to explore the effect and mechanism of moxibustion in preventing and treating migraine.

METHODS

Forty male SD rats were randomly divided into a blank group, a model group, a prevention+treatment (PT) group and a treatment group, 10 rats in each group. Except the blank group, the rats in the remaining groups were injected with nitroglycerin subcutaneously to prepare migraine model. The rats in the PT group were treated with moxibustion 7 days before modeling (once a day) and 30 min after modeling, while the rats in the treatment group were treated with moxibustion 30 min after modeling. The "Baihui" (GV 20) and "Dazhui" (GV 14) were taken for 30 minutes each time. The behavioral scores in each group were observed before and after modeling. After intervention, ELISA method was used to detect the serum level of β-EP and SP; the immunohistochemistry method was used to detect the number of positive cells of IL-1β in brainstem; the Western blot method was used to detect the expression of COX-2 protein in brainstem.

RESULTS

Compared with the blank group, the behavioral scores in the model group were increased 0-30 min, 60-90 min and 90-120 min after modeling (P<0.01); compared with the model group, in the treatment group and the PT group, the behavioral scores were decreased 60-90 min and 90-120 min after modeling (P<0.01). Compared with the blank group, in the model group, the serum level of β-EP was decreased (P<0.01), while the serum level of SP, the number of positive cells of IL-1β in brainstem and the expression of COX-2 protein were increased (P<0.01). Compared with the model group, in the PT group and and the treatment group, the serum level of β-EP was increased (P<0.01), while the serum level of SP, the number of positive cells of IL-1β and the expression of COX-2 protein in brainstem were decreased (P<0.01, P<0.05). Compared with the treatment group, in the PT group, the serum level of β-EP was increased and COX-2 protein expression was decreased (P<0.05).

CONCLUSION

Moxibustion could effectively relieve migraine. The mechanism may be related to reduce the serum level of SP, IL-1β and COX-2 protein expression in brainstem, and increase the serum level of β-EP, and the optimal effect is observed in the PT group.

Gut microbiota modulates visceral sensitivity through calcitonin gene-related peptide (CGRP) production

Abdominal pain is common in patients with gastrointestinal disorders, but its pathophysiology is unclear, in part due to poor understanding of basic mechanisms underlying visceral sensitivity. Accumulating evidence suggests that gut microbiota is an important determinant of visceral sensitivity. Clinical and basic research studies also show that sex plays a role in pain perception, although the precise pathways are not elucidated. We investigated pain responses in germ-free and conventionally raised mice of both sexes, and assessed visceral sensitivity to colorectal distension, neuronal excitability of dorsal root ganglia (DRG) neurons and the production of substance P and calcitonin gene-related peptide (CGRP) in response to capsaicin or a mixture of G-protein coupled receptor (GPCR) agonists. Germ-free mice displayed greater in vivo responses to colonic distention than conventional mice, with no differences between males and females. Pretreatment with intracolonic capsaicin or GPCR agonists increased responses in conventional, but not in germ-free mice. In DRG neurons, gut microbiota and sex had no effect on neuronal activation by capsaicin or GPCR agonists. While stimulated production of substance P by DRG neurons was similar in germ-free and conventional mice, with no additional effect of sex, the CGRP production was higher in germ-free mice, mainly in females. Absence of gut microbiota increases visceral sensitivity to colorectal distention in both male and female mice. This is, at least in part, due to increased production of CGRP by DRG neurons, which is mainly evident in female mice. However, central mechanisms are also likely involved in this process.

NF-κB-Associated Pain-Related Neuropeptide Expression in Patients with Degenerative Disc Disease

The role of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) has been highlighted in mechanisms underlying inflammatory and neuropathic pain processes. The present study was designed to investigate whether NF-κB signaling is associated with pain-related neuropeptide expression in patients with chronic back pain related to degenerative disc disease (DDD). Intervertebral disc (IVD) tissues were collected from forty DDD patients undergoing disc replacement or fusion surgery, and from eighteen postmortem (PM) control subjects. RELA, NFKB1, CGRP, TAC1, TRPV1, and MMP-3 gene expression were analyzed by RT-qPCR, while NF-κB subunit RelA and NF-κB1⁻DNA binding in nuclear extracts and calcitonin gene related peptide (CGRP), substance P (SP), and transient receptor potential, subfamily V, member 1 (TRPV1) protein levels in cytosolic extracts of tissues were assessed by enzyme-linked immunosorbent assay (ELISA). An upregulated NF-κB1⁻DNA binding, and higher CGRP and TRPV1 protein levels were observed in DDD patients compared to PM controls. In DDD patients, NF-κB1⁻DNA binding was positively correlated with nuclear RelA levels. Moreover, NF-κB1⁻DNA binding was positively associated with TRPV1 and MMP-3 gene and SP and TRPV1 protein expression in DDD patients. Our results indicate that the expression of SP and TRPV1 in IVD tissues was associated with NF-κB activation. Moreover, NF-κB may be involved in the generation or maintenance of peripheral pain mechanisms by the regulation of pain-related neuropeptide expression in DDD patients.

Activation of orexin-1 receptors in the ventrolateral periaqueductal grey matter (vlPAG) modulates pulpal nociception and the induction of substance P in vlPAG and trigeminal nucleus caudalis

AIM

To characterize the role of orexin-1 receptors (OX1Rs) in ventrolateral periaqueductal grey matter (vlPAG) on modulation of capsaicin-induced pulpal nociception in rats.

METHODOLOGY

Sixty-six adult male Wistar rats (2 months old) weighing between 230 and 260 g were used. The animals were cannulated for microinjection of drugs into the vlPAG matter. Pulpalgia was induced by intradental application of capsaicin solution (100 μg) into the incisor teeth of the rats. Ten min prior to capsaicin application, orexin-A (50, 100 and 150 pmol L^-1 per rat) was administered. Orexin-A (150 pmol L^-1 ) was also co-administrated with SB-334867 (40 nmol L^-1 per rat), an OX1Rs antagonist; or bicuculline (1 μg per rat), a GABAA receptors antagonist. Moreover, treatment effects on the release of pro-nociceptive modulator substance P (SP) in vlPAG and trigeminal nucleus caudalis (Vc) of rats were explored using an immunofluorescence technique. One-way analysis of variance was used for the statistical analysis.

RESULTS

Orexin-A dose-dependently decreased capsaicin-induced nociceptive behaviour. However, SB-334867 (40 nmol L^-1 per rat) pretreatment (P < 0.05), but not bicuculline (1 μg per rat), attenuated the analgesic effect of orexin-A (150 pmol L^-1 ). The level of SP was significantly increased in Vc and decreased in vlPAG of capsaicin-treated rats (P < 0.05). Capsaicin-induced changes in SP levels, however, were prohibited by orexin-A treatment (150 pmol L^-1 ) (P < 0.05).

CONCLUSIONS

Orexin-A administration into the vlPAG was associated with an inhibitory effect on capsaicin-induced pulpal nociception and bidirectional effects on the induction of SP in vlPAG and Vc of rats. Central activation of OX1Rs is a potential therapeutic tool for pulpalgia.

[Effect of transcutaneous electrical acupoint stimulation on postoperative analgesia of ureteroscopic holmium laser lithotripsy]

OBJECTIVE

To explore the effect of transcutaneous electrical acupoint stimulation (TEAS) on postoperative analgesia of ureteroscopic holmium laser lithotripsy.

METHODS

One hundred and twenty adult patients, American Association of Anesthesiologists (ASA) Class Ⅰ or Ⅱ, scheduled to ureteroscopic holmium laser lithotripsy, were randomly assigned into an observation group and a control group, 60 cases in each one. The patients in the observation group were treated with TEAS for postoperative analgesia. TEAS was implemented at bilateral Shenshu (BL 23) and Yinlingquan (SP 9) at the time of back ward and postoperative 4 h, 8 h, 12 h. TEAS at 7:00, 11:00 and 15:00 at the above acupoints were used on the second and third days; while placebo (twice a day, 100 mg a time) was used. Tramadol hydrochloride tablets for postoperative analgesia were applied in the contnol group, twice a day, 100 mg a time, and electrode sheets without stimulation were put on Shenshu (BL 23) and Yinlingquan (SP 9). When analgesia was insufficient with the score of visual analogue scale (VAS)≥3, the patients were treated with tramadol tablets for remedy analgesia. The VAS score, the concentrations of serotonin (5-HT) and substance P (SP) in 3 mL venous blood at the time of back ward (T₀), postoperative 4 h (T₁), 12 h (T₂), 24 h (T₃), and 48 h (T₄) were detected respectively. The total amount of medication for remedy analgesia and the incidence of adverse reactions, such as nausea and vomiting within postoperative 48 h were compared between the two groups.

RESULTS

The VAS scores at T₁ through T₄ were lower than those at T₀ in the two groups (all P<0.05). Compared with the control group, the VAS scores at T₁ through T₃ in the observation group were lower (all P<0.05). The total dose of remedy analgesic medicine within 48 h after operation in the observation group was lower than that in the control group (P<0.05). Compared with the control group, the concentrations of 5-HT at T₁, T₂, T₄ and SP at T₁ through T₄ were lower (all P<0.05). The numbers of constipation, nausea and vomiting in the observation group were less than those in the control group (both P<0.05).

CONCLUSION

TEAS can relieve the pain and reduce the total amount of analgesic medicine, the levels of substance causing pain and the incidence of adverse reactions after ureteroscopic holmium laser lithotripsy.

[Time-effect relationship and molecular mechanism of electroacupuncture for repair of gastric mucosal lesion]

OBJECTIVE

To dynamically observe the effects of electroacupuncture (EA) on repair of gastric mucosal lesion in rats with gastric ulcer, and to explore the time-effect relationship and molecular mechanism of EA for gastric ulcer.

METHODS

A total of 72 SD rats were randomly assigned to a normal group, a model group, a acupoint group and a sham acupoint group, and each group were further divided into a 1-day subgroup, a 4-day subgroup and a 7-day subgroup, 6 rats in each subgroup. The rat model of gastric ulcer was established by using intragastric administration of ethyl alcohol. The rats in the acupoint group were treated with EA at"Zusanli"(ST 36) and"Liangmen"(ST 21); the rats in the sham acupoint group were treated with EA at points 5 mm next to"Zusanli"(ST 36) and"Liangmen"(ST 21); the EA was given 30 min per treatment, once a day. The rats in the normal group and model group were treated with immobilization for 30 min per day, and no EA was given. PR-PCR method was applied to test the expression of proliferating cell nuclear antigen (PCNA) and substance P (SP); Western blot method was applied to test the expression of neurotensin (NT).

RESULTS

After 1-day treatment, the ulcer index in the model group was higher than that in the normal group (P<0.01), and the expression of PCNA, SP and NT was decreased (P<0.01, P<0.05); compared with the model group and sham acupoint group, the ulcer index was decreased in the acupoint group (both P<0.05), and the expression of PCNA and SP was up-regulated (all P<0.05) while that of NT was up-regulated (both P<0.01). After 4-day treatment, the ulcer index in the model group was reduced but still higher than that in the normal group (P<0.05), and the expression of PCNA, SP and NT was up-regulated and higher than that in the normal group (all P<0.01); the ulcer index in the acupoint group was similar to that in the normal group (P>0.05), and the expression of PCNA and SP was lower than that in the model group (P<0.01, P<0.05), and the expression of NT was not significantly different from that in the model group (P>0.05). After 7-day treatment, the differences of indexes above were not significant among the four groups (all P>0.05).

CONCLUSION

EA at acupoints of stomach meridian has two-way regulation on PCNA and SP and improve the expression of NT in different pathological state of gastric ulcer, which could further improve the repair of gastric ulcer.

The mechanism of μ-opioid receptor (MOR)-TRPV1 crosstalk in TRPV1 activation involves morphine anti-nociception, tolerance and dependence

Initiated by the activation of various nociceptors, pain is a reaction to specific stimulus modalities. The μ-opioid receptor (MOR) agonists, including morphine, remain the most potent analgesics to treat patients with moderate to severe pain. However, the utility of MOR agonists is limited by the adverse effects associated with the use of these drugs, including analgesic tolerance and physical dependence. A strong connection has been suggested between the expression of the transient receptor potential vanilloid type 1 (TRPV1) ion channel and the development of inflammatory hyperalgesia. TRPV1 is important for thermal nociception induction, and is mainly expressed on sensory neurons. Recent reports suggest that opioid or TRPV1 receptor agonist exposure has contrasting consequences for anti-nociception, tolerance and dependence. Chronic morphine exposure modulates TRPV1 activation and induces the anti-nociception effects of morphine. The regulation of many downstream targets of TRPV1 plays a critical role in this process, including calcitonin gene-related peptide (CGRP) and substance P (SP). Additional factors also include capsaicin treatment blocking the anti-nociception effects of morphine in rats, as well as opioid modulation of TRPV1 responses through the cAMP-dependent PKA pathway and MAPK signaling pathways. Here, we review new insights concerning the mechanism underlying MOR-TRPV1 crosstalk and signaling pathways and discuss the potential mechanisms of morphine-induced anti-nociception, tolerance and dependence associated with the TRPV1 signaling pathway and highlight how understanding these mechanisms might help find therapeutic targets for the treatment of morphine induced antinociception, tolerance and dependence.

Small constrained SP1-7 analogs bind to a unique site and promote anti-allodynic effects following systemic injection in mice

Previous results have shown that the substance P (SP) N-terminal fragment SP1-7 may attenuate hyperalgesia and produce anti-allodynia in animals using various experimental models for neuropathic pain. The heptapeptide was found to induce its effects through binding to and activating specific sites apart from any known neurokinin or opioid receptor. Furthermore, we have applied a medicinal chemistry program to develop lead compounds mimicking the effect of SP1-7. The present study was designed to evaluate the pharmacological effect of these compounds using the mouse spared nerve injury (SNI) model of chronic neuropathic pain. Also, as no comprehensive screen with the aim to identify the SP1-7 target has yet been performed we screened our lead compound H-Phe-Phe-NH2 toward a panel of drug targets. The extensive target screen, including 111 targets, did not reveal any hit for the binding site among a number of known receptors or enzymes involved in pain modulation. Our animal studies confirmed that SP1-7, but also synthetic analogs thereof, possesses anti-allodynic effects in the mouse SNI model of neuropathic pain. One of the lead compounds, a constrained H-Phe-Phe-NH2 analog, was shown to exhibit a significant anti-allodynic effect.