Characterisation of Peptide5 systemic administration for treating traumatic spinal cord injured rats

Abstract

Systemic administration of a Connexin43 mimetic peptide, Peptide5, has been shown to reduce secondary tissue damage and improve functional recovery after spinal cord injury (SCI). This study investigated safety measures and potential off-target effects of Peptide5 systemic administration. Rats were subjected to a mild contusion SCI using the New York University impactor. One cohort was injected intraperitoneally with a single dose of fluorescently labelled Peptide5 and euthanised at 2 or 4 h post-injury for peptide distribution analysis. A second cohort received intraperitoneal injections of Peptide5 or a scrambled peptide and was culled at 8 or 24 h post-injury for the analysis of connexin proteins and systemic cytokine profile. We found that Peptide5 did not cross the blood-spinal cord barrier in control animals, but reached the lesion area in the spinal cord-injured animals without entering non-injured tissue. There was no evidence that the systemic administration of Peptide5 modulates Connexin43 protein expression or hemichannel closure in the heart and lung tissue of SCI animals. The expression levels of other major connexin proteins including Connexin30 in astrocytes, Connexin36 in neurons and Connexin47 in oligodendrocytes were also unaltered by systemic delivery of Peptide5 in either the injured or non-injured spinal cords. In addition, systemic delivery of Peptide5 had no significant effect on the plasma levels of cytokines, chemokines or growth factors. These data indicate that the systemic delivery of Peptide5 is unlikely to cause any off-target or adverse effects and may thus be a safe treatment option for traumatic SCI.

The Connexin Mimetic Peptide Gap27 and Cx43-Knockdown Reveal Differential Roles for Connexin43 in Wound Closure Events in Skin Model Systems

“…Other studies by Gourdie and colleagues used a peptide targeting the carboxyl tail of Cx43 and its binding site with the PDZ domain to improve wound healing, resolve inflammation and reduce scarring in rat models and recently in human clinical trials [ 33 , 34 , 35 ]. Studies using Pep5, based on the Gap27 sequence, have shown remarkable effects on tissue repair and inflammation in the retina, cornea and spinal cord [ 36 , 37 , 38 ]. Recent studies using Gap27 have also shown that this peptide is effective in improving rabbit corneal wound healing [ 39 ] and in primary human gingival fibroblasts, isolated from donors aged 26–48 years of age [ 29 ].…”

Connexin Hemichannels in Astrocytes: Role in CNS Disorders

“…Though the interaction between Cx43 and molecules involved in pain offers a complicated feedback loop in pain development and maintenance, based on the current studies, strategies to suppress the function of Cx43 may be a robust approach for pain relief (Wu et al, 2011; Chen et al, 2012, 2014; Shen et al, 2014; Xu et al, 2014; Neumann et al, 2015; Robinson and Dougherty, 2015; Choi et al, 2016; Hang et al, 2016; Kaji et al, 2016; Mao et al, 2017a,b; Wang and Sun, 2017; Yang et al, 2018).…”

“…The expression changes of Cx43 following pain is still inconclusive (Table 2). Multiple studies have shown that Cx43 is upregulated in astrocytes following nerve ligation and spinal cord injury, and that inhibition of Cx43 can attenuate pain hypersensitivity (Wu et al, 2011; Chen et al, 2012, 2014, 2018; Shen et al, 2014; Neumann et al, 2015; Robinson and Dougherty, 2015; Choi et al, 2016; Hang et al, 2016; Kaji et al, 2016; Mao et al, 2017a,b; Wang and Sun, 2017; Yang et al, 2018). On the contrary, few studies showed that a decrease of Cx43 following nerve injury could contribute to pain hypersensitivity (Xu et al, 2014; Morioka et al, 2015; Zhang et al, 2016).…”

“…There are a few ways to distinguish hemichannels and gap junctions. For example, when used for short incubation time or at a low concentration, peptide 5, a mimetic of Cx43, can only inhibit hemichannels, but when applied for a long incubation time or at a long concentration, can attenuate both hemichannels and gap junctions (Choi et al, 2016; Mao et al, 2017a). Another approach to distinguish Cx43 gap junction and hemichannels are using the dyes uptaken.…”

Therapeutic repair for spinal cord injury: combinatory approaches to address a multifaceted problem

“…Since neuroinflammation has both beneficial and detrimental effects, broadspectrum suppression of inflammation may not be efficacious. Neuroprotection can also be achieved through preventing glutamate excitotoxicity by blockade of NMDA receptors by magnesium (Ditor et al, 2007) or gacyclidine (Feldblum et al, 2000), blockade of tetrodotoxin-sensitive sodium channels using riluzole (Satkunendrarajah et al, 2016), preventing apoptosis using erythropoietin (Baptiste & Fehlings, 2006), inhibition of connexin hemichannels using a mimetic peptide (Mao et al, 2017), mild to moderate hypothermia (Dietrich et al, 2009) and many more strategies (Baptiste & Fehlings, 2006;Thuret et al, 2006). These more discrete manipulations of secondary processes may prove to have greater therapeutic benefit than the broad approaches.…”