Neuroprotective Effect of Ramipril Is Mediated by AT2 in a Mouse MODEL of Paclitaxel-Induced Peripheral Neuropathy

The role of ACE inhibitors and ARBs in preserving cognitive function via hypertension Management: A critical Update

Hypertension poses a significant risk to cognition-related disorders like dementia. As the global population ages, age-related neurological illnesses such as Alzheimer's disease are becoming increasingly prevalent. The primary hypertension treatments, angiotensin receptor blockers, and angiotensin-converting enzyme inhibitors, exhibit neuroprotective properties. However, observational studies suggest that they may independently contribute to cognitive decline and dementia. Some of these medications have shown promise in reducing cognitive impairment and amyloid buildup in Alzheimer's models. While direct comparisons between the two drug classes are limited, angiotensin receptor blockers have been associated with less brain shrinkage, lower dementia incidence, and slower cognitive decline compared to angiotensin-converting enzyme inhibitors. Both types of medications can influence cognition by passing the blood-brain barrier, with angiotensin receptor blockers potentially offering superior neuroprotective effects due to their selective blockade of the angiotensin type 1 receptor.

Current understanding of the link between angiotensin-converting enzyme and pain perception

The renin-angiotensin system (RAS) is known to affect diverse physiological processes that affect the functioning of many key organs. Angiotensin-converting enzyme (ACE) modulates a variety of bioactive peptides associated with pain. ACE inhibitors (ACEis) have found applications in the treatment of cardiovascular, kidney, neurological and metabolic disorders. However, ACEis also tend to display undesirable effects, resulting in increased pain sensitization and mechanical allodynia. In this review, we provide comprehensive discussion of preclinical and clinical studies involving the evaluation of various clinically approved ACEis. With the emerging knowledge of additional factors involved in RAS signaling and the indistinct pharmacological role of ACE substrates in pain, extensive studies are still required to elucidate the mechanistic role of ACE in pain perception.

Biological Mediators and Partial Regulatory Mechanisms on Neuropathic Pain Associated With Chemotherapeutic Agents

One of the most common issues caused by antineoplastic agents is chemotherapy-induced peripheral neuropathy (CIPN). In patients, CIPN is a sensory neuropathy accompanied by various motor and autonomic changes. With a high prevalence of cancer patients, CIPN is becoming a major problem for both cancer patients and for their health care providers. Nonetheless, there are lacking effective interventions preventing CIPN and treating the CIPN symptoms. A number of studies have demonstrated the cellular and molecular signaling pathways leading to CIPN using experimental models and the beneficial effects of some interventions on the CIPN symptoms related to those potential mechanisms. This review will summarize results obtained from recent human and animal studies, which include the abnormalities in mechanical and temperature sensory responses following chemotherapy such as representative bortezomib, oxaliplatin and paclitaxel. The underlying mechanisms of CIPN at cellular and molecular levels will be also discussed for additional in-depth studies needed to be better explored. Overall, this paper reviews the basic picture of CIPN and the signaling mechanisms of the most common antineoplastic agents in the peripheral and central nerve systems. A better understanding of the risk factors and fundamental mechanisms of CIPN is needed to develop effective preventive and therapeutic strategies.

A mouse model of sensory neuropathy induced by a long course of monomethyl-auristatin E treatment

Antibody-drug conjugates (ADCs) are anticancer drugs consisting of a monoclonal antibody, targeting selective tumor antigens, to which has been frequently associated a highly potent cytotoxic agent, the monomethyl auristatin E (MMAE) using a chemical linker. MMAE is a tubulin polymerization inhibitor derived from dolastin-10. These MMAE-ADCs are responsible for peripheral nerve toxicities. Our objective was to develop and characterize a mouse model of MMAE-induced peripheral neuropathy induced by free MMAE injections. MMAE was injected in Swiss mice at 50 μg/kg i.p. every other day for 7 weeks. Assessments of motor and sensory nerve functions were performed once a week on MMAE and Vehicle-treated mice. Sciatic nerve and paw skin were removed at the end of experiment for subsequent immunofluorescence and morphological analysis. MMAE did not affect motor coordination, muscular strength and heat nociception, but significantly induced tactile allodynia in MMAE-treated mice compared with Vehicle-treated mice from day 35 to day 49. MMAE significantly reduced myelinated and unmyelinated axon densities in sciatic nerves and led to a loss of intraepidermal nerve fiber in paw skin. In summary, long course of low dose of MMAE induced a peripheral sensory neuropathy associated with nerve degeneration, without general state alteration. This model may represent a ready accessible tool to screen neuroprotective strategies in the context of peripheral neuropathies induced by MMAE-ADCs.

Angiotensin-Related Peptides and Their Role in Pain Regulation

Angiotensin (Ang)-generating system has been confirmed to play an important role in the regulation of fluid balance and blood pressure and is essential for the maintenance of biological functions. Ang-related peptides and their receptors are found throughout the body and exhibit diverse physiological effects. Accordingly, elucidating novel physiological roles of Ang-generating system has attracted considerable research attention worldwide. Ang-generating system consists of the classical Ang-converting enzyme (ACE)/Ang II/AT1 or AT2 receptor axis and the ACE2/Ang (1-7)/MAS1 receptor axis, which negatively regulates AT1 receptor-mediated responses. These Ang system components are expressed in various tissues and organs, forming a local Ang-generating system. Recent findings indicate that changes in the expression of Ang system components under pathological conditions are involved in the development of neuropathy, inflammation, and their associated pain. Here, we summarized the effects of changes in the Ang system on pain transmission in various organs and tissues involved in pain development process.

Fluocinolone Acetonide Enhances Anterograde Mitochondria Trafficking and Promotes Neuroprotection against Paclitaxel-Induced Peripheral Neuropathy

Paclitaxel (PTX)-induced peripheral neuropathy (PIPN) is a debilitating health condition which is a result of degeneration of peripheral nerves found in extremities. Currently, there are no established treatment methods that can prevent or protect from PIPN. Fluocinolone acetonide (FA) has been recently identified as a potential candidate for protection from PIPN. However, the fundamental mechanism of action is still unknown. In this study, we showed that enhanced anterograde mitochondrial movement in dorsal root ganglion (DRG) cells has a major role in FA-mediated neuroprotection in PIPN. In this study, cells were treated with PTX or FA along with their combination followed by mitochondrial fluorescence staining. Somal (proximal) and axonal (distal) mitochondria were selectively stained using a microfluidic compartmentalized chamber with different MitoTrackers blue and red, respectively, which we termed, the two-color staining approach. Results revealed that axons were protected from degeneration by the PTX effect when treated along with FA. PTX exposure alone resulted in low mitochondrial mobility in DRG cells. However, cotreatment with PTX and FA showed significant enhancement of anterograde trafficking of somal (proximal) mitochondria to distal axons. Similarly, cotreatment with FA restored mitochondrial mobility significantly. Overall, this study affirms that increasing mitochondrial recruitment into the axon by cotreatment with FA can be a worthwhile strategy to protect or prevent PIPN. The proposed two-color staining approach can be extended to study trafficking for other neuron-specific subcellular organelles.

Blockade of Cholecystokinin Type 2 Receptors Prevents the Onset of Vincristine-Induced Neuropathy in Mice

Vincristine (VCR) is responsible for the onset of the VCR-induced peripheral neuropathy (VIPN), associated with neuropathic pain. Several reports have strongly linked the cholecystokinin type 2 receptor (CCK2R) to nociceptive modulation. Thus, our aim was to evaluate the effect of CCK2R blockade on the onset of VIPN, as well as its interaction on VCR anticancer efficacy. VCR was administrated in mice for 8 days (100 µg/kg/d, i.p.). Transcriptomic analysis of the dorsal root ganglia (DRG) was performed at day 7 in VCR and control mice. Proglumide (30 mg/kg/d), a CCK1R and CCK2R antagonist, and Ly225910 (1 mg/kg/d), a selective CCK2R antagonist, were administrated one day before and during VCR treatment. Tactile sensitivity was assessed during treatments. Immunofluorescence and morphological analyses were performed on the skin, DRG and sciatic nerve at day 7. The cytotoxicity of VCR in combination with proglumide/Ly225910 was evaluated in human cancer cell lines. Cck2r was highly upregulated in the DRG of VCR mice. Proglumide accelerated the recovery of normal sensitivity, while Ly225910 totally prevented the onset of allodynia and nerve injuries induced by VCR. Proglumide or Ly225910 in combination with VCR did not affect the cytotoxicity of VCR. Targeting CCK2R could therefore be an effective strategy to prevent the onset of VIPN.