Angiotensin (1-7) Attenuates the Nociceptive Behavior Induced by Substance P and NMDA via Spinal MAS1

Covid-19 infection as a possible risk factor for longitudinally extensive transverse myelitis!

INTRODUCTION

There is limited data about the neurological effects of Covid-19 in infected patients. In this report, we present 2 LETM cases that are possibly associated with Covid-19 infection.

METHODS

Here, we present 2 cases that subsequently developed LETM following Covid-19 infection. The first case presented a finding of tetraparesis prominent in the lower extremities that started ten days after the Covid-19 infection. The second patient was admitted with paraparesis and urinary-stool retention on the 12th day from the onset of symptoms of Covid-19 infection.

RESULTS

In these 2 cases, LETM developing following Covid'19 infection was associated with Covid-19 infection. Although Covid-19 PCR was negative in the CSF of both patients, the Covid-19 PCR test was positive in the samples taken from the oropharynx.

CONCLUSION

The mechanism of LETM caused by Covid-19 infection is not clearly known. However, both direct infection of the spinal cord and excessive inflammatory response to primary Covid-19 infection may cause spinal cord damage. Therefore, possible Covid-19-associated myelitis should be kept in mind in cases of long segment transverse myelitis grouped under the title of NMOSD and without any etiological factor.

Tachykinins and the potential causal factors for post-COVID-19 condition

The most prevalent symptoms of post-COVID-19 condition are pulmonary dysfunction, fatigue and muscle weakness, anxiety, anosmia, dysgeusia, headaches, difficulty in concentrating, sexual dysfunction, and digestive disturbances. Hence, neurological dysfunction and autonomic impairments predominate in post-COVID-19 condition. Tachykinins including the most studied substance P are neuropeptides expressed throughout the nervous and immune systems, and contribute to many physiopathological processes in the nervous, immune, gastrointestinal, respiratory, urogenital, and dermal systems and participate in inflammation, nociception, and cell proliferation. Substance P is a key molecule in neuroimmune crosstalk; immune cells near the peripheral nerve endings can send signals to the brain with cytokines, which highlights the important role of tachykinins in neuroimmune communication. We reviewed the evidence that relates the symptoms of post-COVID-19 condition to the functions of tachykinins and propose a putative pathogenic mechanism. The antagonism of tachykinins receptors can be a potential treatment target.

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.

RNA-seq analysis revealed genes associated with neuropathic pain induced by chronic compressive injury in interferon regulatory factors 4 knockout mice

OBJECTIVE

To explore the differential expression of genes between wild-type chronic compressive injury (CCI) mice (WT-CCI) and interferon regulatory factors 4 (IRF4) knockout CCI mice (KO-CCI) by RNA-seq analysis of the mouse spinal cord.

METHODS

RNA-seq analysis of the spinal cord tissue of the chronic sciatic nerve ligation mice and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were used.

RESULTS

A total of 104 genes were up-regulated and 116 genes were down-regulated in spinal cord of the mice in IRF4 knockout (KO-CCI) group compared with that in the wild-type CCI (WT-CCI) group. There were 1472 differentially expressed genes in the biological process group, 62 differentially expressed genes in the cellular component group, and 163 differentially expressed genes in the molecular function group in KO-CCI mice. A total of 14 genes related to inflammatory reactions were differentially expressed. Real-time PCR results confirmed that Pparg and Grpr mRNA expression was up-regulated and Arg 1 and Ccl11 mRNA expression was down-regulated in the KO-CCI group.

CONCLUSION

IRF4 is involved in neuropathic pain in CCI mice, IRF4 may participate in neuropathic pain by regulating Grpr, Mas1, Galr3, Nos2, Arg1, Ccl11, Ptgs2, S100a8, Pparg, Cd40, Has2, Gpr151, Il123a, Capns2, Ankrd1, Ccnb1, and Nppb genes.

COVID-19-Associated Acute Transverse Myelitis: A Case Series of a Rare Neurologic Condition

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral infection is not confined to the respiratory system, but has also shown extra-pulmonary invasion including the nervous system. About 36.4% of hospitalized patients in China with confirmed coronavirus disease 2019 (COVID-19) infection had neurological manifestations. SARS-CoV-2 virus enters the human body through angiotensin converting enzyme-2 (ACE-2) receptors on the surface of human cells and causes disease. ACE2 receptors are also expressed on the surface of spinal cord cells. More rare neurologic conditions have been reported in the literature to be associated with COVID-19 such as acute transverse myelitis (ATM), Guillain Barre syndrome, acute flaccid myelitis, etc. We report two cases of confirmed COVID-19 who presented four to five days of their COVID-19 symptoms and progressive bilateral lower limb weakness and urinary retention.

ATM is an acquired spinal cord disorder. ATM is a relatively common neurological complication of COVID-19, accounting for 1.2% of all neurological complications associated with COVID-19. The mechanism by which COVID-19 causes ATM is not completely understood but has been assumed to be due to the structural resemblance of RNA viruses. Entrance of SARS-CoV-2 to the nervous system can take place through two pathways, either directly or indirectly. The direct pathway is through trans-synaptic transmission from the peripheral nervous system or by hematogenous spread into the blood-brain barrier through ACE-2, while the indirect pathway is through a systemic immune response.

Shedding Light on the Pharmacological Interactions between μ-Opioid Analgesics and Angiotensin Receptor Modulators: A New Option for Treating Chronic Pain

The current protocols for neuropathic pain management include µ-opioid receptor (MOR) analgesics alongside other drugs; however, there is debate on the effectiveness of opioids. Nevertheless, dose escalation is required to maintain their analgesia, which, in turn, contributes to a further increase in opioid side effects. Finding novel approaches to effectively control chronic pain, particularly neuropathic pain, is a great challenge clinically. Literature data related to pain transmission reveal that angiotensin and its receptors (the AT1R, AT2R, and MAS receptors) could affect the nociception both in the periphery and CNS. The MOR and angiotensin receptors or drugs interacting with these receptors have been independently investigated in relation to analgesia. However, the interaction between the MOR and angiotensin receptors has not been excessively studied in chronic pain, particularly neuropathy. This review aims to shed light on existing literature information in relation to the analgesic action of AT1R and AT2R or MASR ligands in neuropathic pain conditions. Finally, based on literature data, we can hypothesize that combining MOR agonists with AT1R or AT2R antagonists might improve analgesia.