SAFit2 ameliorates paclitaxel-induced neuropathic pain by reducing spinal gliosis and elevating pro-resolving lipid mediators

BACKGROUND

Chemotherapy-induced neuropathic pain (CIPN) describes a pathological pain state that occurs dose-dependently as a side effect and can limit or even impede an effective cancer therapy. Unfortunately, current treatment possibilities for CIPN are remarkably confined and mostly inadequate as CIPN therapeutics themselves consist of low effectiveness and may induce severe side effects, pointing out CIPN as pathological entity with an emerging need for novel treatment targets. Here, we investigated whether the novel and highly specific FKBP51 inhibitor SAFit2 reduces paclitaxel-induced neuropathic pain.

METHODS

In this study, we used a well-established multiple low-dose paclitaxel model to investigate analgesic and anti-inflammatory properties of SAFit2. For this purpose, the behavior of the mice was recorded over 14 days and the mouse tissue was then analyzed using biochemical methods.

RESULTS

Here, we show that SAFit2 is capable to reduce paclitaxel-induced mechanical hypersensitivity in mice. In addition, we detected that SAFit2 shifts lipid levels in nervous tissue toward an anti-inflammatory and pro-resolving lipid profile that counteracts peripheral sensitization after paclitaxel treatment. Furthermore, SAFit2 reduced the activation of astrocytes and microglia in the spinal cord as well as the levels of pain-mediating chemokines. Its treatment also increased anti-inflammatory cytokines levels in neuronal tissues, ultimately leading to a resolution of neuroinflammation.

CONCLUSIONS

In summary, SAFit2 shows antihyperalgesic properties as it ameliorates paclitaxel-induced neuropathic pain by reducing peripheral sensitization and resolving neuroinflammation. Therefore, we consider SAFit2 as a potential novel drug candidate for the treatment of paclitaxel-induced neuropathic pain.

Analysis of the Selective Antagonist SAFit2 as a Chemical Probe for the FK506-Binding Protein 51

The FK506-binding protein 51 (FKBP51) has emerged as an important regulator of the mammalian stress response and is involved in persistent pain states and metabolic pathways. The FK506 analog SAFit2 (short for selective antagonist of FKBP51 by induced fit) was the first potent and selective FKBP51 ligand with an acceptable pharmacokinetic profile. At present, SAFit2 represents the gold standard for FKBP51 pharmacology and has been extensively used in numerous biological studies. Here we review the current knowledge on SAFit2 as well as guidelines for its use.

SAFit2 reduces neuroinflammation and ameliorates nerve injury-induced neuropathic pain

Background

Neuropathic pain is experienced worldwide by patients suffering from nerve injuries, infectious or metabolic diseases or chemotherapy. However, the treatment options are still limited because of low efficacy and sometimes severe side effects. Recently, the deficiency of FKBP51 was shown to relieve chronic pain, revealing FKBP51 as a potential therapeutic target. However, a specific and potent FKBP51 inhibitor was not available until recently which hampered targeting of FKBP51.

Methods

In this study, we used the well-established and robust spared nerve injury model to analyze the effect of SAFit2 on nerve injury-induced neuropathic pain and to elucidate its pharmacodynamics profile. Therefore, the mice were treated with 10 mg/kg SAFit2 after surgery, the mice behavior was assessed over 21 days and biochemical analysis were performed after 14 and 21 days. Furthermore, the impact of SAFit2 on sensory neurons and macrophages was investigated in vitro.

Results

Here, we show that the FKBP51 inhibitor SAFit2 ameliorates nerve injury-induced neuropathic pain in vivo by reducing neuroinflammation. SAFit2 reduces the infiltration of immune cells into neuronal tissue and counteracts the increased NF-κB pathway activation which leads to reduced cytokine and chemokine levels in the DRGs and spinal cord. In addition, SAFit2 desensitizes the pain-relevant TRPV1 channel and subsequently reduces the release of pro-inflammatory neuropeptides from sensory neurons.

Conclusions

SAFit2 ameliorates neuroinflammation and counteracts enhanced neuronal activity after nerve injury leading to an amelioration of nerve injury-induced neuropathic pain. Based on these findings, SAFit2 constitutes as a novel and promising drug candidate for the treatment of nerve injury-induced neuropathic pain.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02615-7.

Macrocyclic FKBP51 Ligands Define a Transient Binding Mode with Enhanced Selectivity

Subtype selectivity represents a challenge in many drug discovery campaigns. A typical example is the FK506 binding protein 51 (FKBP51), which has emerged as an attractive drug target. The most advanced FKBP51 ligands of the SAFit class are highly selective vs. FKBP52 but poorly discriminate against the homologs and off-targets FKBP12 and FKBP12.6. During a macrocyclization pilot study, we observed that many of these macrocyclic analogs have unanticipated and unprecedented preference for FKBP51 over FKBP12 and FKBP12.6. Structural studies revealed that these macrocycles bind with a new binding mode featuring a transient conformation, which is disfavored for the small FKBPs. Using a conformation-sensitive assay we show that this binding mode occurs in solution and is characteristic for this new class of compounds. The discovered macrocycles are non-immunosuppressive, engage FKBP51 in cells, and block the cellular effect of FKBP51 on IKKα. Our findings provide a new chemical scaffold for improved FKBP51 ligands and the structural basis for enhanced selectivity.

Structure-Based Design of High-Affinity Macrocyclic FKBP51 Inhibitors

The FK506-binding protein 51 (FKBP51) emerged as a key player in several diseases like stress-related disorders, chronic pain, and obesity. Linear analogues of FK506 called SAFit were shown to be highly selective for FKBP51 over its closest homologue FKBP52, allowing the proof-of-concept studies in animal models. Here, we designed and synthesized the first macrocyclic FKBP51-selective ligands to stabilize the active conformation. All macrocycles retained full FKBP51 affinity and selectivity over FKBP52 and the incorporation of polar functionalities further enhanced affinity. Six high-resolution crystal structures of macrocyclic inhibitors in complex with FKBP51 confirmed the desired selectivity-enabling binding mode. Our results show that macrocyclization is a viable strategy to target the shallow FKBP51 binding site selectively.

It is not worthwhile to perform ileoscopy on all patients

BACKGROUND

It remains controversial whether ileoscopy should be attempted in all patients. Although the ease of ileoscopy and the diagnostic yield have been well described, there have been no studies describing the value of the diagnostic yield in altering clinical management. We carried out a study to ascertain whether it is worthwhile to perform ileoscopy in all patients having a colonoscopy.

METHODS

We carried out a retrospective study of all patients who had a colonoscopy between January 1, 2002, and December 31, 2003. The patient details, indications, findings, and complications of the procedure were recorded, together with the histopathology reports of colonic and terminal ileal biopsies. Clinical case note of patients with a positive diagnosis was reviewed to ascertain whether there was a change to the patient's management following an abnormal biopsy result.

RESULTS

A total of 2,149 colonoscopies were performed. In 346 patients (16.1%), the terminal ileum was intubated. There were 16 abnormal findings on histology, which gave a diagnostic yield of 4.6% of all ileoscopies. A change to management occurred in only half of these patients.

CONCLUSION

Ileoscopy should only be attempted in situations in which the indication is warranted and that would alter management. It is not cost-effective to carry out ileoscopy on all patients.

Colonoscopy in the very old: why bother?

OBJECTIVES

To evaluate the use of colonoscopy in patients aged at least 85 years. Does the ideal of an ageism free service apply?

DESIGN

A retrospective audit.

SETTING

Department of gastroenterology that carries out about 1000 colonoscopies annually in a district general hospital serving a population of about 320 000.

SUBJECTS

All patients aged at least 85 years who underwent colonoscopy over five years to 2003.

MAIN OUTCOME MEASURES

The indications for colonoscopy and its findings. The outcome of patients found to have colonic cancers.

RESULTS

Colonoscopy was completed in 219 cases (69%). The main reasons for failure were poor bowel preparation and severe diverticular disease. Normal findings occurred in 65 (30%) of the 219 cases that had had a complete examination. Colonoscopy identified a problem that explained the patient's symptoms in 116 (37%) cases. Polyps were found in 45 (14.2%) cases and malignancy in 28 (8.8%).

CONCLUSIONS

The absence of significant complications and comparatively high yield of colonic malignancies and polyps reinforces the value of colonoscopy as a diagnostic tool even after 85 years of age and despite the technical challenges of the procedure in this age group that limited completion. Increasing age alone should not preclude a patient from colonoscopy.

Intravenous hyoscine as a premedication for colonoscopy: a randomized double-blind controlled trial

BACKGROUND AND STUDY AIMS

There is wide variation in the use of antispasmodics to facilitate colonoscopy, both within and between countries, and its use before such procedures remains controversial. The aim of this study was to determine whether there was any objective benefit in using hyoscine as a premedication for colonoscopy in a district general hospital.

PATIENTS AND METHODS

Consecutive day-case patients undergoing colonoscopy were included in the study. They were prospectively randomly allocated to receive either intravenous hyoscine (n = 61) or intravenous placebo (n = 56) as part of their premedication.

RESULTS

Our analysis demonstrated no statistically significant difference between the two groups with respect to the median time from colonoscope insertion to caecal intubation (9.7 minutes in the hyoscine group vs. 8.3 minutes in the placebo group) or the median total procedure time (14.8 minutes in the hyoscine group vs. 13.8 minutes in the placebo group). There was also no statistically significant difference in success rates for caecal intubation between the two groups ( P < 0.06). However a type II error cannot be excluded because of the small sample size.

CONCLUSION

This study demonstrated no obvious benefit in the routine use of hyoscine as a premedication for colonoscopy in a district general hospital setting.

The future health-care worker: health-care practitioner

Changes in working patterns, advances in technology and changing patients' expectations are increasing the difficulties with recruitment and retention of appropriately skilled health-care staff (Hutchinson et al, 2001). This has resulted in increasing difficulty in meeting the population's health-care needs. Newer ways of working that may attract additional staff into the service and better ways of deploying the resources of new and existing staff may help ease the problem. This editorial considers one such initiative: the health-care practitioner (HCP) model that is being piloted in general (internal) medicine at Kingston Hospital, a district general hospital to the south west of London.

Exercise-induced rhabdomyolysis: even the fit may suffer

Keeping fit has its risks. We describe the case of a 29-year-old woman who presented with rhabdomyolysis following non-exhaustive exercise. Cases of exercise-induced rhabdomyolysis have been reported in unfit individuals or those attempting exhaustive exercise such as marathon running or weight lifting but are unusual in fit individuals making modest changes to their normal fitness routine. Renal failure is the most serious complication of rhabdomyolysis but is apparently rarer when the rhabdomyolysis is caused by exercise. Surprisingly the published literature does not help us advise patients on the risk of suffering further episodes of acute rhabdomyolysis with further exercise. We suggest that, regardless of a person's fitness, when starting a new exercise he or she does so gradually.

Clinical protocols are key to quality health care delivery

The use of clinical protocols allows health care providers to offer appropriate diagnostic treatment and care services to patients, variance reports to purchasers and quality training to clinical staff. Such protocols provide a locally agreed standard to which clinicians and the organization can work and against which they can be audited. By embedding protocols into patients' records and reporting by exception, the use of protocols may help to tackle a raft of other issues successfully such as the reduction in junior doctors' hours, and the facilitation of shared care. It may also bolster the medico-legal robustness of the health care delivered. If the protocols are sufficiently detailed, costing, coding and other resource usage information can flow directly from the clinical records. Such benefits may be maximized by using protocols within the framework of an electronic patient record system.