targeted-toxins

Q: What are neuropeptide-toxins and how do they work?

A: Neuropeptide-toxin conjugates are made up of the ribosome-inactivating protein, saporin, coupled to a naturally-occurring or synthetically-modified neuropeptide such as Substance P or dermorphin. The conjugate has binding specificity similar to the native, unconjugated neuropeptide. When the neuropeptide binds to its cognate receptor, the conjugate is internalized. Once inside the target cell within an endosome, the neuropeptide and saporin separate and some of the saporin translocates into the cytoplasm where it catalytically inactivates ribosomes resulting in cell death.

Q: Are neuropeptide-toxins effective suicide transport agents?

A: The general answer to this question is not currently known. However, in the instance of intrathecally injected dermorphin-SAP (Cat. #IT-12), the evidence does NOT favor suicide transport of the neuropeptide-toxin conjugate. When supramaximal doses of dermorphin-SAP (750 ng) are injected into the lumbar subarachnoid space of adult rats, less than 1% of lumbar dorsal root ganglion cells show evidence of saporin activity. This is in spite of the fact that many of these neurons express the targeted mu opioid receptor on their central terminals in the superficial dorsal horn of the spinal cord. This assertion is based on analysis of over 16,000 neurons from dorsal root ganglia in six rats.

See: Targeted Toxins

Alhassan M (2022) Sensory and motor visual functions in Parkinson’s Disease with respect to freezing of gait symptoms. J Ophthalmol & Vis Sci 7(2):1069.

Objective: This review article summarizes the results from previous studies focusing on visual functions in Parkinson’s Disease patients.

Summary: Freezing of gait (FOG) is considered to be a motor disorder symptom that affects some Parkinson Disease (PD) patients; however, it is hypothesized that sensory systems may also be involved in FOG. Visual functions include high contrast visual acuity, low contrast visual acuity, contrast sensitivity, Vernier acuity, mesopic vision, stereopsis, motion perception, and vergence eye movements and are all affected in PD patients with FOG patients having more deficits in some of these functions. FOG patients also had impairments in non-dopaminergic mediated functions which suggests greater impairment in two functions that involve cholinergic neurotransmitters. 192-IgG-SAP (Cat. IT-01) was used to create a PD rat animal model to study the contribution of the cholinergic system to motor functions. It was found that the fall rates were more frequent in rats, that were injected with dual 192 IgG-saporin /6-hydroxydopamine (6-OHDA) than rats with either isolated cholinergic or isolated dopaminergic lesions.

Related Products: 192-IgG-SAP (Cat. #IT-01)

See Also:

• Kucinski A et al. Modeling fall propensity in Parkinson’s disease: deficits in the attentional control of complex movements in rats with cortical-cholinergic and striatal-dopaminergic deafferentation. J Neurosci 33(42):16522-16539, 2013.

Levine AS, Jewett DC, Kotz CM, Olszewski PK (2022) Behavioral plasticity: Role of neuropeptides in shaping feeding responses. Appetite 174:106031. doi: 10.1016/j.appet.2022.106031 PMID: 35395362

Objective: Review studies on feeding behavior involving neuropeptides that influence behavioral plasticity – primarily opioids, orexin, neuropeptide Y, and oxytocin.

Summary: Eating behavior is influenced by a number of external factors, including time of day, type of food available, energy balance state, and stressors. The reviewed work underscores that environmental factors play a critical role in feeding behavior and energy balance, but changes in eating behavior also result from a multitude of non-environmental factors, such that there can be no single mechanism or variable that can explain ingestive behavior.

Usage: References a previous publication using Oxytocin-SAP (IT-46).

Related Products: Oxytocin-SAP (Cat. #IT-46)

See Also:

• Baskin DG et al. A new oxytocin-saporin cytotoxin for lesioning oxytocin-receptive neurons in the rat hindbrain. Endocrinology 151(9):4207-4213, 2010.

Murphy ER, Thompson R, Osman KL, Haxton C, Brothers M, Lee L, Warncke K, Smith CL, Keilholz AN, Hamad A, Golzy M, Bunyak F, Ma L, Nichols NL, Lever TE (2022) A strength endurance exercise paradigm mitigates deficits in hypoglossal-tongue axis function, strength, and structure in a rodent model of hypoglossal motor neuron degeneration. Front Neurosci 16:869592. doi: 10.3389/fnins.2022.869592 PMID: 35844238

Objective: To investigate the effect of high-repetition/low-resistance tongue exercise on tongue function, strength, and structure.

Summary: The tongue plays a crucial role in swallowing and impairment can lead to dysphagia, particularly in motor neuron diseases such as amyotrophic lateral sclerosis. This study utilized the authors previously established inducible rodent model of dysphagia due to targeted degeneration of the hypoglossal-tongue axis by injecting cholera toxin B conjugated to saporin (CTB-SAP) into the genioglossus muscle of the tongue base for retrograde transport to the hypoglossal (XII) nucleus via the hypoglossal nerve, which provides the sole motor control of the tongue. Results showed that sham-exercised CTB-SAP rats had significant deficits in lick rate, swallow timing, and lick force. In exercised CTB-SAP rats, lick rate and lick force were preserved; however, swallow timing deficits persisted.

Usage: Rats received either a single “control” injection of unconjugated CTB + SAP (20μg CTB+25μg SAP) or CTB-SAP (Cat. #IT-14) injection (25μg of CTB conjugated to SAP) into the midline genioglossus muscle in the tongue base.

Related Products: CTB-SAP (Cat. #IT-14), Saporin (Cat. #PR-01)

Zhang JJ, Song CG, Dai JM, Li L, Yang XM, Chen ZN (2022) Mechanism of opioid addiction and its intervention therapy: Focusing on the reward circuitry and mu-opioid receptor. MedComm 3(3):e148. doi: 10.1002/mco2.148 PMID: 35774845

Objective: To examine the mechanism of opioid addiction, with a specific focus on the reward circuitry and the role of the mu-opioid receptor, and to explore potential intervention therapies.

Summary: The authors discuss the neurobiological processes underlying addiction and highlight the importance of understanding these mechanisms in developing effective intervention therapies for opioid addiction.

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12)

See Also:

• Jenrette TA et al. Lesions of the patch compartment of dorsolateral striatum disrupt stimulus-response learning. Neuroscience 415:161-172, 2019.

Liu AL, Liu YF, Wang G, Shao YQ, Yu CX, Yang Z, Zhou ZR, Han X, Gong X, Qian KW, Wang LQ, Ma YY, Zhong YM, Weng SJ, Yang XL (2022) The role of ipRGCs in ocular growth and myopia development. Sci Adv 8(23):eabm9027. doi: 10.1126/sciadv.abm9027 PMID: 35675393

Objective: To provide evidence in a mouse model to demonstrate that intrinsically photosensitive retinal ganglion cells (ipRGCs) make a considerable contribution to the establishment of the ocular refractive system.

Summary: The involvement of ipRGCs in mouse refractive development was investigated with selective ipRGC ablation using Melanopsin-SAP. The authors found that ipRGCs are substantially involved in ocular refractive development in mice, which is crucial for image-forming visual functions. This conclusion is derived from the considerable myopic refractive shifts induced in the eyes when most ipRGCs were ablated, yet they exhibited hyperopic shifts when ipRGCs were selectively activated.

Usage: C57BL/6 mice received intravitreal injection of Melanopsin-SAP (IT-44) at three concentrations [200, 400, and 800 ng, all suspended in 0.75 µl of 0.1 M PBS (pH 7.4)] at postnatal day 18; control eyes received the same volume of PBS or 400 ng of nonspecific antibody–conjugated saporin (IgG-SAP, also in 0.75 µl of PBS).

Related Products: Melanopsin-SAP (Cat. #IT-44), Rabbit IgG-SAP (Cat. #IT-35), Melanopsin Rabbit Polyclonal, affinity-purified (Cat. #AB-N39)

Griffin JM, Healy FM, Dahal LN, Floisand Y, Woolley JF (2022) Worked to the bone: antibody-based conditioning as the future of transplant biology. J Hematol Oncol 15(1):65. doi: 10.1186/s13045-022-01284-6

Objective: To analyze the current status of antibody-based drugs in pre-transplant conditioning regimens and assess their potential in the future of transplant biology.

Summary: This review article suggests that antibody-based conditioning regimens may be the next big advancement in hematopoietic stem cell transplantation.

Related Products: Anti-CD117-SAP (Cat. #IT-83)

See Also:

• Palchaudhuri R et al. Non-genotoxic conditioning for hematopoietic stem cell transplantation using a hematopoietic-cell-specific internalizing immunotoxin. Nat Biotechnol 34:738-745, 2016.
• Castiello MC et al. Efficacy and safety of anti-CD45-saporin as conditioning agent for RAG deficiency. J Allergy Clin Immunol 147(1):309-320.e6, 2021.
• Czechowicz A et al. Selective hematopoietic stem cell ablation using CD117-antibody-drug-conjugates enables safe and effective transplantation with immunity preservation. Nat Commun 10:617, 2019.
• Li Z et al. Hematopoietic chimerism and donor-specific skin allograft tolerance after non-genotoxic CD117 antibody-drug-conjugate conditioning in MHC-mismatched allotransplantation. Nat Commun 10:616, 2019.

Krieger JP, Asker M, Van der Velden P, Börchers S, Richard JE, Maric I, Longo F, Singh A, De Larigue G, Skibicka KP (2022) Neural pathway for gut feelings: vagal interoceptive feedback from the gastrointestinal tract is a critical modulator of anxiety-like behavior. Biological Psychiatry in press. doi: 10.1016/j.biopsych.2022.04.020

Objective: To determine how the sensing of gastrointestinal state affects anxiety.

Summary: Vagal sensory signals from the gastrointestinal tract are critical for baseline and feeding-induced tuning of anxiety via the central amygdala in rats. The article results suggest vagal gut-brain signaling as a target to normalize interoception in anxiety.

Usage: 1.5 ul of CCK-SAP or Blank-SAP were delivered into each nodose ganglion at 250 ng/ul.

Related Products: CCK-SAP (Cat. #IT-31), Blank-SAP (Cat. #IT-21)

Ahn JP (2022) Ablation of dorsomedial striatum patch compartment results in modification to reward-driven behaviors in rats. Mercer University School of Medicine Thesis.

Objective: This thesis intended to demonstrate that selective ablation of dorsomedial striatum (DMS) patch compartment neurons results in a significant impact on the initial development of reward-driven behaviors during the early stages of drug seeking behavior.

Summary: Through the use Dermorphin-SAP and training rats to self-administer cocaine, ablation of the patch compartment of the DMS resulted in an increase in early-stage lever pressing, suggesting that the DMS patch compartment contributes to reward-driven behaviors.

Usage: 17 ng/µl Dermorphin-SAP in sterile artificial cerebrospinal fluid (aCSF) to selectively ablate patch compartment neurons. Infusions into either the dorsomedial striatum or dorsolateral striatum (2 µl of infusion liquid).

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12)

Bosecke C (2022) A novel anxiety process biomarker via electrovestibulography. University of Manitoba Thesis.

Objective: Use electrophysiological technique of Electrovestibulography to measure field potentials caused by vestibular neurons in the ear canal in order to identify biomarkers associated with anxiety disorder.

Summary: Anxiety disorders have no known biomarkers and are diagnosed based on symptoms. Identifying biomarkers could help improve the accuracy of anxiety disorder diagnosis, but can be difficult because the brain regions implicated in anxiety are very deep within the brain.

Usage: 192 IgG-SAP (Cat. #IT-01) was used to lesion the cholinergic medial septum inputs to the hippocampus. 192 IgG-saporin was diluted to 0.35 µg/µl with sterile saline, and 0.4 µl was infused bilaterally into each ventral site of the medial septum.

Related Products: 192-IgG-SAP (Cat. #IT-01)