Angioni L, Cocco C, Ferri G, Argiolas A, Melis M, Sanna F (2016) Involvement of nigral oxytocin in locomotor activity: A behavioral, immunohistochemical and lesion study in male rats. Horm Behav 83:23-38. doi: 10.1016/j.yhbeh.2016.05.012
Summary: Oxytocin is well known for its hormonal role in lactation and parturition, but also exerts widespread actions in central nervous system. Previous experiments revealed the existence of a correlation between the changes in locomotor activity found in Oxytocin-SAP-treated rats and the extent of the changes in nigral TH and vesicular glutamate transporters immunoreactivity, provide support for a modulatory role of oxytocin on locomotor activity at the level of the substantia nigra. The day after a prior assessment of spontaneous locomotor activity, rats were randomly injected bilaterally with 0.3 μL of Oxytocin-SAP (Cat. #IT-46, 60 ng/μL/site), or with the same amount of Blank-SAP (Cat. #IT-21, 60 ng/μL/site) or with vehicle (0.3 μL/site of PBS, pH 7.4). Whether oxytocin may be considered as a target for controlling motor disturbances, as those occurring in Parkinson’s disease and/or in other motor disturbances related to basal ganglia dysfunctions, remains to be evaluated
Lee S, Diener K, Kaufman S, Krieger J, Pettersen K, Jejelava N, Arnold M, Watts A, Langhans W (2016) Limiting glucocorticoid secretion increases the anorexigenic property of Exendin-4. Mol Metab 5:552-565. doi: 10.1016/j.molmet.2016.04.008
Summary: Glucagon-like peptide-1 (GLP-1) analogs lower blood surgar levels and cause a loss of appetite. Exendin-4 (Ex-4) is a GLP-1 receptor agonist, and also increases glucocorticoid secretion. Several tests were conducted to determine if the released glucocorticoids interact with Ex-4’s anorexigneic effect. One method involved ablating hindbrain catecholaminergic neurons by stereotaxically injecting 42 ng of Anti-DBH-SAP (Cat. #IT-03) bilaterally into the paraventricular nucleus of the hypothalamus in rats. Animals were injected with equimolar concentrations of unconjugated Saporin (Cat. #PR-01) as a control. Anti-DBH-SAP lesions reduced the efficacy of Ex-4 to increase corticosterone secretion but increased the anorexigenic effect, indicating that Ex-4-dependent corticosterone secretion opposes Ex-4’s actions. Anti-DBH-SAP lesions increased Ex-4’s ability to reduce food intake and body weight.
Over the years, ATS has frequently been asked about Saporin’s safety for use in the lab as well as when used clinically. Residual awareness of alternate Ribosome-Inactivating Proteins (RIPs) and ‘toxins’ such as Ricin have caused some researchers new to the use of RIPs to question the belief that Saporin is safe. Unlike Type 2 RIPs (such as Ricin), Type I RIPs, like Saporin have no binding chain and consequently no means of entering the physiological space necessary for the protein to act as a toxin. The following is a review of safety in handling and potential toxicity within the human body for systemic events not related to normal research applications of Saporin conjugates, including Substance P-Saporin (SP-SAP), which is a therapeutic under development for the treatment of chronic pain.
The acute LD50 for saporin in mice (25 g) is 6.8 mg/kg;[1] that would translate in humans (75 kg) to 510 mg! A concentration of about 100 nM is the threshold to see even a vague hint of saporin toxicity. In human blood, that would correspond to 24 mg injected systemically into a person. The fermentation process to produce recombinant saporin has a titer of 2 mg/L meaning that the production broth itself contains no more than 67 nM concentration of saporin. Furthermore, the final protein concentrations from production batches of recombinant Saporin used in our drug are 4 mg/ml, meaning 6 mL of final material would need to accidentally end up in a human before the ‘hint of toxicity’ threshold would potentially be met.
The toxicology studies of SP-SAP contained within ATS’s IND prior to the current human Phase I clinical trial evaluated effects related to the intended method of administration, intrathecal local injection. SP-SAP is not expected to ever be a self-administered therapy, so the effects of gross off-target events, such as accidental auto-injection, swallowing, spillage, or immersion were not considered.
The table below[2] highlights antibody-saporin conjugates approved by the FDA for Phase I/II clinical trials in humans. The therapeutics listed below were administered intravenously and imply what the FDA accepted as non-toxic levels of saporin-based conjugates in these studies.
Looking more closely at the study by French et al.,[3] several milligrams of antibody conjugate were repeatedly injected into human patients under a FDA regulated clinical trial and peak serum levels tested, demonstrating rapid clearing of saporin from the system.
As a company that specializes in Saporin, our two-plus decades of experience working with the protein in research, preclinical, and clinical environments has taught us that with minimal standard laboratory precautions users are not at any real risk of toxic effects. Even our CSO, after 30+ years of working with Saporin exhibits undetectable levels of Saporin antibodies in his blood!
Vierck C, Yezierski R, Wiley R (2016) Pain sensitivity following loss of cholinergic basal forebrain (CBF) neurons in the rat. Neuroscience 319:23-34. doi: 10.1016/j.neuroscience.2016.01.038
Objective: There is a large amount of research on the involvement of cholinergic mechanisms on spinal transmission of pain signals, indicating that cholinergic agonists can attenuate this kind of pain. In contrast, some studies have shown affective reactions to pain are suppressed by cholinergic antagonists. The authors investigated the disagreement between reflexive and affective reactions.
Summary: Lesioned rats displayed decreased escape from thermal stimulation, as well as loss of the normal hyperalgesic effect of sound stress. Results indicate that the basal forebrain cholinergic system plays a role in central processing of pain.
Usage: Administration of 192-IgG-SAP with a 4-μg injection into the left lateral ventricle of rats. Animals were tested in temperature escape and sound stress models.
Schwartz M, Nguyen A, Warrier D, Palmerston J, Thomas A, Morairty S, Neylan T, Kilduff T (2016) Locus coeruleus and tuberomammillary nuclei ablations attenuate hypocretin/orexin antagonist-mediated rem sleep. eNeuro 3:ENEURO.0018-0016.2016. doi: 10.1523/ENEURO.0018-16.2016
Summary: To examine the mechanism by which the Orexin 1r/Orexin 2r antagonist almorexant decreases wakefulness and increases NREM and REM sleep the authors utilized Anti-DBH-SAP (Cat. #IT-03) and Orexin-B-SAP (Cat. #IT-20). Rats received 3-μg injections of Anti-DBH-SAP into the LC, or bilateral 57-80 ng injections of Orexin-SAP into the TMN. Both conjugates attenuated the increased REM sleep seen upon administration of almorexant without altering almorexant-induced changes in NREM sleep.
Yao Y, Echeverry S, Shi X, Yang M, Yang Q, Wang G, Chambon J, Wu Y, Fu K, De Koninck Y, Zhang J (2016) Dynamics of spinal microglia repopulation following an acute depletion. Sci Rep 6:22839. doi: 10.1038/srep22839
Summary: This study confirms that similar to microglia in the brain, spinal microglia can repopulate rapidly following elimination, which is driven essentially by a self-renewal process. To deplete microglia in spinal cords, Mac-1-SAP (Cat. #IT-06) was injected i.t. (7 μl, 1.6 μg/μl) at the level of L4-L5 in mouse. The results support the concept that microglia repopulation, whether in the brain or in the spinal cord, is the consequence of onsite resident microglia proliferation. Newly generated microglia are fully functional and are able to respond to peripheral nerve injury and contribute to the development of neuropathic pain.
Fei Y, Wang X, Chen S, Zhou Q, Zhang C, Li Y, Sun L, Zhang L (2016) Role of the RVM in descending pain regulation originating from the cerebrospinal fluid-contacting nucleus. Neurochem Res 41:1651-1661. doi: 10.1007/s11064-016-1880-6
Summary: The researchers investigated whether the CSF-contacting nucleus contributed to descending pain modulation in normal and neuropathic rats, and detected the 5-HT expression changes in both RVM and spinal dorsal cord. They also detected the possible anatomical and function correlation between the CSF-contacting nucleus and the RVM. Targeted ablation of the CSF-contacting nucleus was performed using CTB-SAP (Cat. #IT-14; 500 ng/3 μl), which was administered i.c.v. to the normal rats and rats 7 days before the CCI procedure. Based on the findings of the present study, they believe that the CSF-contacting nucleus may act as a component of descending pain regulation system. RVM, which acts as an important brain nucleus, is involved in the relay of nociceptive information between the CSF-contacting nucleus and spinal cord. Moreover, RVM 5-HT system plays a critical role in descending pain inhibition originating from the CSF-contacting nucleus.
Gritsch S, Bali K, Kuner R, Vardeh D (2016) Functional characterization of a mouse model for central post-stroke pain. Mol Pain 12:1744806916629049. doi: 10.1177/1744806916629049
Summary: While clinical evidence has pointed toward central pain pathway dysfunction in central post-stroke pain (CPSP), the underlying mechanisms have not been defined. In this work the authors created a mouse model of CPSP through lesions of the thalamic ventral posterolateral nucleus. In order to examine the role of neurokinin-1 receptor-expressing (NK1R) neurons in lamina I/III of the spinal cord in the development and maintenance of CPSP the authors administered 1 μmol intrathecal injections of SSP-SAP (Cat. #IT-11). Saporin (Cat. #PR-01) was used as a control. While the NK1R+ neurons in the spinal cord were not involved in establishing CPSP, the data indicate that sensory changes in the mice are comparable to those observed in human patients with CPSP.
Wang L, Conner J, Nagahara A, Tuszynski M (2016) Rehabilitation drives enhancement of neuronal structure in functionally relevant neuronal subsets. Proc Natl Acad Sci U S A 113:2750-2755. doi: 10.1073/pnas.1514682113
Summary: Rehabilitation is often prescribed after brain injury, but the basis for how training can influence brain plasticity and recovery is unclear. In this study, the authors show that intense rehabilitation training after focal brain injury drives significant structural changes in brain cells located adjacent to the injury. Importantly, a key brain modulatory system, the basal forebrain cholinergic system, is required for enabling rehabilitation to impact brain structure. Rats underwent cholinergic ablations by injecting 192-IgG-Saporin (Cat. #IT-01) into the nucleus basalis (0.2-0.25 mcl of 0.375 mg/ml solution in artificial CSF). Damage to the cholinergic system, which can occur naturally during aging, completely blocks brain plasticity mediated by rehabilitation and significantly attenuates functional recovery. These results provide new insights into how rehabilitation may promote recovery and suggest that brain cholinergic systems may be a possible therapeutic target for influencing recovery.
